{"gene":"PIAS1","run_date":"2026-06-10T06:43:35","timeline":{"discoveries":[{"year":1998,"finding":"PIAS1 specifically inhibits STAT1-mediated gene activation by blocking the DNA binding activity of Stat1; PIAS1 physically associates with Stat1 (but not Stat2 or Stat3) after cytokine stimulation, and this interaction requires Stat1 phosphorylation on Tyr-701.","method":"Coimmunoprecipitation, DNA binding assays, reporter gene assays, yeast two-hybrid","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP, DNA binding assay, reporter assay, replicated across multiple labs subsequently","pmids":["9724754"],"is_preprint":false},{"year":2000,"finding":"The COOH-terminal domain of PIAS1 (aa 392–541) directly interacts with the NH2-terminal domain of Stat1 (aa 1–191), and PIAS1 specifically recognizes the dimeric form of Stat1 rather than the monomer; the NH2-terminal region of PIAS1 acts as a modulatory domain preventing interaction with Stat1 monomers.","method":"Yeast two-hybrid, in vitro binding assays, domain deletion mutants, modified yeast two-hybrid for dimer vs. monomer discrimination","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — in vitro direct binding plus yeast two-hybrid with domain mapping, single lab but multiple orthogonal methods","pmids":["10805787"],"is_preprint":false},{"year":2001,"finding":"PIAS1 functions as a SUMO E3 ligase for p53: it binds SUMO-1 and Ubc9 (the E2), catalyzes p53 sumoylation in vitro and in cells, and a RING finger-like domain mutation abolishes Ubc9 binding and ligase activity while retaining p53/SUMO-1 binding.","method":"Yeast two-hybrid, in vitro SUMOylation assay, cell-based SUMOylation assay, RING domain mutagenesis","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution of E3 activity, active-site mutagenesis, replicated in multiple subsequent studies","pmids":["11583632"],"is_preprint":false},{"year":2002,"finding":"PIAS1 acts as a SUMO E3 ligase for the transcription factor Sp3, stimulating SUMO conjugation at a single lysine in the IKXE motif; PIAS1 interacts with both Sp3 and Ubc9, and SUMO modification of Sp3 silences its transcriptional activity without altering DNA-binding specificity or affinity.","method":"In vitro and in vivo SUMOylation assays, mutagenesis, GST pulldown, reporter assays","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution plus mutagenesis plus functional transcription assays, single lab multiple orthogonal methods","pmids":["12356736"],"is_preprint":false},{"year":2002,"finding":"PIAS1 (and PIASxα) act as SUMO E3 ligases for the androgen receptor (AR), enhancing AR sumoylation in an RING finger-like domain-dependent manner; ligand (testosterone) binding to AR is required for sumoylation in intact cells, and PIAS1-mediated sumoylation represses AR-dependent transcription.","method":"Cell-based and in vitro SUMOylation assays, RING domain mutagenesis, reporter gene assays","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution plus active-site mutagenesis plus functional transcription assays, single lab","pmids":["12177000"],"is_preprint":false},{"year":2002,"finding":"PIAS1 activates p53-mediated transcription independently of its RING finger (sumoylation) domain; PIAS1 interacts with the tetramerization and C-terminal regulatory domains of p53, and endogenous PIAS1 co-immunoprecipitates with endogenous p53.","method":"Yeast two-hybrid, coimmunoprecipitation, reporter gene assays, RING domain deletion mutant","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — Co-IP plus reporter assay plus domain mutants, single lab","pmids":["11788578"],"is_preprint":false},{"year":2003,"finding":"PIAS1 interacts with and sumoylates focal adhesion kinase (FAK) at Lys-152; sumoylation promotes FAK nuclear localization and dramatically increases FAK autophosphorylation at Tyr-397 in intact cells and in kinase assays, independently of cell adhesion.","method":"Yeast two-hybrid, in vitro binding, coimmunoprecipitation, cell-based SUMOylation, kinase assays, mutagenesis, subcellular fractionation","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — multiple orthogonal methods including in vitro assay, kinase assay, mutagenesis, fractionation, single lab","pmids":["14500712"],"is_preprint":false},{"year":2004,"finding":"PIAS1 sumoylates p73α (but not C-terminally truncated isoforms p73β and p73γ) through its RING finger domain; PIAS1 binding stabilizes p73, sumoylated p73 is restricted to the nuclear matrix, PIAS1-mediated sumoylation decreases p73 transcriptional activity, and PIAS1 overexpression reduces cells in G1 via reduced p21 transcription whereas PIAS1 siRNA causes G2 arrest.","method":"Yeast two-hybrid, pulldown, coimmunoprecipitation, cell-based SUMOylation, reporter assays, RNAi, cell cycle analysis","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — multiple orthogonal methods (CoIP, sumoylation assay, RNAi, functional reporter, cell cycle), single lab","pmids":["15572666"],"is_preprint":false},{"year":2004,"finding":"NMR structure of the N-terminal domain (residues 1–65) of PIAS1 revealed a four-helix SAP domain; this domain binds p53 (GST pulldown) and has strong affinity toward A/T-rich DNA, with the binding site mapping to one end of the four-helix bundle fitting the minor groove.","method":"NMR spectroscopy, GST pulldown, gel mobility shift assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — structure determined by NMR with biochemical binding validation, single lab","pmids":["15133049"],"is_preprint":false},{"year":2004,"finding":"PIAS1 is required for the innate immune response in vivo: Pias1−/− cells show that PIAS1 selectively inhibits a subset of IFN-γ– or IFN-β–inducible genes by interfering with STAT1 recruitment to gene promoters; Pias1−/− mice exhibit enhanced antiviral activity and increased protection against pathogenic infection.","method":"Knockout mouse (Pias1−/−), chromatin immunoprecipitation, gene expression analysis","journal":"Nature immunology","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean KO with defined cellular phenotype plus ChIP mechanism, replicated in vivo","pmids":["15311277"],"is_preprint":false},{"year":2004,"finding":"SNM1A physically interacts with PIAS1 and they colocalize at nuclear foci; point mutations in the SNM1 domain that disrupt PIAS1 interaction cause mislocalization of SNM1A and loss of complementation of ICL repair defects, demonstrating PIAS1 interaction is required for SNM1A-mediated DNA interstrand cross-link repair.","method":"Coimmunoprecipitation, colocalization, mutagenesis, genetic complementation in DT40 cells","journal":"Molecular and cellular biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP plus colocalization plus mutagenesis plus genetic complementation, single lab","pmids":["15572677"],"is_preprint":false},{"year":2005,"finding":"PIAS1 negatively regulates NF-κB signaling: upon cytokine stimulation, the p65 subunit of NF-κB translocates to the nucleus where it interacts with PIAS1; PIAS1 blocks p65 DNA binding activity in vitro and in vivo, and Pias1−/− cells show increased p65 occupancy at NF-κB target gene promoters.","method":"Knockout mouse, coimmunoprecipitation, in vitro DNA binding assay, chromatin immunoprecipitation, microarray","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — KO mouse plus Co-IP plus in vitro and in vivo DNA binding assays, multiple orthogonal methods","pmids":["15657437"],"is_preprint":false},{"year":2005,"finding":"PIAS1 interacts with and sumoylates metabotropic glutamate receptor 8 (mGluR8) C-terminal domain; PIAS1 binding requires a region N-terminal to the consensus sumoylation motif and sumoylation occurs at Lys-882 within that motif in HEK293 cells.","method":"Yeast two-hybrid, GST pulldown, cell-based SUMOylation, mutagenesis","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — yeast two-hybrid confirmed by GST pulldown and in-cell sumoylation with mutagenesis, single lab","pmids":["16144832"],"is_preprint":false},{"year":2005,"finding":"PIAS1 activates smooth muscle cell differentiation marker genes (SM α-actin, SM MHC, SM22α) by interacting with serum response factor (SRF) and class I bHLH proteins (E2-2, E12); PIAS1 is required for SRF binding to the SM α-actin promoter in intact chromatin, and its effect requires SRF.","method":"Yeast two-hybrid, mammalian two-hybrid, coimmunoprecipitation, reporter assays, RNAi, chromatin immunoprecipitation, SRF−/− embryonic stem cells","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (CoIP, ChIP, KO cells, RNAi) in single lab","pmids":["16135793"],"is_preprint":false},{"year":2006,"finding":"PIAS1 confers DNA-binding specificity on the Msx1 homeoprotein by regulating its subnuclear localization to the nuclear periphery; interaction with PIAS1 (not sumoylation per se) is required for Msx1 to repress myogenic genes (MyoD, Myf5) and inhibit myoblast differentiation; myogenic regulatory genes repressed by Msx1 also localize at the nuclear periphery.","method":"Coimmunoprecipitation, live imaging, subnuclear localization assays, mutagenesis, reporter assays, RNAi","journal":"Genes & development","confidence":"High","confidence_rationale":"Tier 2 / Moderate — Co-IP plus direct localization experiment plus RNAi functional assay, multiple orthogonal methods single lab","pmids":["16600910"],"is_preprint":false},{"year":2007,"finding":"Proinflammatory stimuli (TNF, LPS) induce IKKα-mediated phosphorylation of PIAS1 at Ser90; this phosphorylation is required for PIAS1 to repress NF-κB target gene transcription and for its rapid recruitment to NF-κB target gene promoters; IKKα (but not IKKβ) interacts with PIAS1 in vivo and mediates this phosphorylation in a SUMO ligase-dependent manner.","method":"Phospho-specific mutants (Ser90A), coimmunoprecipitation, chromatin immunoprecipitation, in vivo interaction assays","journal":"Cell","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — phosphomutant analysis plus Co-IP plus ChIP, single lab but multiple orthogonal methods in high-impact study","pmids":["17540171"],"is_preprint":false},{"year":2007,"finding":"PIAS1 interacts with and represses SOX9 transcriptional activity; PIAS1 enhances SUMOylation of SOX9 at Lys-396, and sumoylated SOX9 has reduced transcriptional activity on reporter constructs; PIAS1 can also repress SUMOylation-deficient SOX9-K396R, indicating additional SUMO ligase-dependent mechanisms.","method":"GST pulldown, coimmunoprecipitation, colocalization in tissue culture and mouse embryos, reporter assays, mutagenesis","journal":"Molecular reproduction and development","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — pulldown plus Co-IP plus reporter assay plus mutagenesis, single lab","pmids":["17440973"],"is_preprint":false},{"year":2007,"finding":"PIAS1 and GATA-3 interact in Th2 cells; PIAS1 functions as a positive transcriptional coregulator for GATA-3 and facilitates GATA-3 recruitment to the IL-13 promoter, enhancing IL-13 expression in a promoter-selective manner.","method":"Coimmunoprecipitation, ChIP, reporter assays, siRNA knockdown, gain-of-function overexpression","journal":"Journal of immunology","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — Co-IP plus ChIP plus functional reporter and siRNA, single lab","pmids":["18056374"],"is_preprint":false},{"year":2009,"finding":"PRMT1 arginine-methylates PIAS1 at Arg-303 in vitro and in vivo upon IFN treatment; methylation-deficient and methylation-mimicking mutants show that this modification is essential for PIAS1 to be recruited to STAT1 target gene promoters in the late IFN response phase, leading to STAT1 release and transcriptional repression.","method":"In vitro methylation assay, mass spectrometry of methylation sites, mutagenesis, chromatin immunoprecipitation, RNAi","journal":"Genes & development","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — in vitro biochemical assay plus mass spectrometry plus mutagenesis plus ChIP, single lab multiple orthogonal methods","pmids":["19136629"],"is_preprint":false},{"year":2009,"finding":"SOCS1, SOCS3, and PIAS1 each promote myogenic differentiation by inhibiting the LIF-induced JAK1/STAT1/STAT3 pathway via distinct targets; PIAS1 targets activated STAT1 and prevents its DNA binding; the SUMO E3 ligase activity of PIAS1 is dispensable for its role in myogenic differentiation.","method":"Reporter assays, RNAi knockdown, overexpression, DNA binding assays, SUMO ligase-dead mutant analysis","journal":"Molecular and cellular biology","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — RNAi plus overexpression plus ligase-dead mutant plus DNA binding assay, single lab","pmids":["19620279"],"is_preprint":false},{"year":2009,"finding":"PIAS1 and PIAS4 are recruited to DNA double-strand break sites via their SAP domains and are required for SUMO1 and SUMO2/3 accumulation at DSB sites; they promote the productive association of 53BP1, BRCA1, and RNF168 with damage sites and are required for ubiquitin adduct formation by RNF8, RNF168, and BRCA1, ultimately promoting DSB repair and conferring ionizing radiation resistance.","method":"Laser micro-irradiation/IRIF assays, SAP domain mutants, siRNA knockdown, epistasis with E3 ligases, repair assays","journal":"Nature","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (IRIF, domain mutants, siRNA, functional epistasis), high-impact journal, subsequently replicated","pmids":["20016603"],"is_preprint":false},{"year":2010,"finding":"PIAS1 restricts natural T regulatory (Treg) cell differentiation by maintaining repressive chromatin at the Foxp3 promoter; PIAS1 binds the Foxp3 promoter and recruits DNA methyltransferases and heterochromatin protein 1 (HP1) for epigenetic modifications; Pias1 deletion causes promoter demethylation, reduced H3K9 methylation, and increased Treg numbers in vivo.","method":"Knockout mouse, ChIP, bisulfite sequencing, chromatin accessibility assays, flow cytometry","journal":"Science","confidence":"High","confidence_rationale":"Tier 2 / Moderate — clean KO mouse plus ChIP plus epigenetic profiling, multiple orthogonal methods","pmids":["20966256"],"is_preprint":false},{"year":2010,"finding":"PIAS1 suppresses TGFβ-induced EMT in mammary epithelial cells in a SUMO ligase-dependent manner; TGFβ downregulates PIAS1 levels during EMT; PIAS1 sumoylates SnoN, and loss of SnoN sumoylation impairs its ability to inhibit TGFβ-induced EMT.","method":"Gain/loss-of-function (overexpression and siRNA), sumoylation assays, mutagenesis of SnoN sumoylation sites, morphological EMT readouts","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — gain/loss of function plus sumoylation assay plus mutagenesis, single lab","pmids":["21103059"],"is_preprint":false},{"year":2010,"finding":"PIAS1 promotes sumoylation of the Gli transcription factors downstream of Hedgehog signaling; expression of SUMO-1 or PIAS1 increases Gli transcriptional activity in vitro; in the embryonic neural tube, forced PIAS1 expression increases Gli activity and induces ectopic Nkx2.2, while a ligase-dead PIAS1 mutant blocks endogenous Nkx2.2 expression.","method":"Cell-based SUMOylation assays, reporter assays, in ovo electroporation in embryonic neural tube, PIAS1 ligase-dead mutant","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro and in vivo (neural tube) functional assays with ligase-dead mutant control, single lab","pmids":["20711444"],"is_preprint":false},{"year":2010,"finding":"PIAS1 regulates subnuclear localization of CP2c and forms a stable hexameric DNA-binding complex with CP2c and CP2b on the α-globin promoter; PIAS1 acts as a SUMO-independent co-activator by bridging two CP2 proteins through distinct interaction domains; PIAS1 knockdown reduces both CP2c and CP2b promoter occupancy.","method":"RNAi knockdown, in vitro DNA binding (EMSA), coimmunoprecipitation, ChIP, nuclear localization assays, domain mapping","journal":"Nucleic acids research","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — in vitro complex reconstitution plus ChIP plus RNAi, single lab","pmids":["20421208"],"is_preprint":false},{"year":2011,"finding":"PIAS1 couples ROS-dependent JNK activation to the SUMO pathway: PIAS1 knockdown prevents ROS-induced hypersumoylation and also enhances JNK signaling; conversely, PIAS1 overexpression inhibits JNK activity independently of its SUMO ligase function, indicating a non-enzymatic function in JNK regulation; PIAS1 knockdown attenuates ROS-dependent apoptosis.","method":"siRNA knockdown, overexpression, JNK activity assays, SUMO ligase-dead mutants, caspase-3/7 activity assays, transcriptomic profiling","journal":"FASEB journal","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — RNAi plus overexpression plus ligase-dead mutant, single lab","pmids":["21676946"],"is_preprint":false},{"year":2012,"finding":"PIAS1 sumoylates PML to promote its CK2-mediated phosphorylation and subsequent ubiquitin/proteasome-mediated degradation, attenuating PML tumor suppressor function; PIAS1-mediated sumoylation of PML-RARA is essential for arsenic trioxide-induced degradation of PML-RARA and apoptosis in APL cells.","method":"Co-IP, SUMOylation assays, proteasome inhibitor studies, siRNA knockdown, apoptosis assays","journal":"Cancer research","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — Co-IP plus sumoylation assay plus functional rescue, single lab","pmids":["22406621"],"is_preprint":false},{"year":2012,"finding":"PIAS1 sumoylates SATB1 at Lys-744, and this sumoylation regulates caspase-6-mediated cleavage of SATB1 at PML nuclear bodies; phosphorylation of SATB1 at Thr-188 inhibits its interaction with the PIAS1 SAP motif and thereby blocks sumoylation; an LXXLL motif (residues 193–197) near the phosphorylation site mediates interaction with the PIAS SAP domain.","method":"Mutagenesis, coimmunoprecipitation, in vitro binding, cell-based sumoylation and cleavage assays","journal":"Molecular and cellular biology","confidence":"Medium","confidence_rationale":"Tier 1–2 / Moderate — mutagenesis plus in vitro binding plus functional cleavage assay, single lab","pmids":["20351170"],"is_preprint":false},{"year":2012,"finding":"PIAS1 is phosphorylated at Ser522 by MAPK-activated protein kinase-2 (MK2); this phosphorylation enhances both PIAS1 SUMO E3 ligase activity (toward p53) and its transrepression activity; PIAS1-S522A mutant fails to promote p53 sumoylation or exert anti-inflammatory effects in endothelial cells in vitro and in vivo.","method":"Phosphomutant analysis (S522A), in vivo p53 sumoylation assay, reporter assays, leukocyte rolling in microvessels (in vivo)","journal":"Arteriosclerosis, thrombosis, and vascular biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — phosphomutant plus in vivo sumoylation plus functional in vitro and in vivo readouts, single lab","pmids":["23202365"],"is_preprint":false},{"year":2013,"finding":"PIAS1 is an E3 SUMO ligase for both Huntingtin (HTT) SUMO-1 and SUMO-2 modification; PIAS1-mediated SUMO-2 modification regulates the accumulation of insoluble HTT; overexpression of PIAS1 increases and knockdown decreases insoluble HTT accumulation; reduction of dPIAS in a mutant HTT Drosophila model is protective.","method":"Systematic E3 SUMO ligase screen, siRNA knockdown, overexpression, insolubility fractionation assays, Drosophila model","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 2 / Moderate — systematic screen plus gain/loss of function plus Drosophila in vivo validation, multiple orthogonal methods","pmids":["23871671"],"is_preprint":false},{"year":2013,"finding":"PIAS1 functions as a SUMO E3 ligase for C/EBPβ through its SAP domain interaction; PIAS1-mediated sumoylation of C/EBPβ promotes its ubiquitination and proteasomal degradation; PIAS1 expression transiently peaks on day 4 of adipocyte differentiation when C/EBPβ declines, and PIAS1 inhibits adipogenesis in a catalytic activity-dependent manner.","method":"Coimmunoprecipitation, in vitro and in vivo sumoylation assays, ubiquitination assays, protein stability assays, RNAi, overexpression, adipogenesis assays","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — in vitro and in vivo sumoylation assay plus ubiquitination/stability assay plus functional differentiation rescue, single lab multiple orthogonal methods","pmids":["24061474"],"is_preprint":false},{"year":2013,"finding":"PIAS1 forms a non-covalent ternary complex with SUMO1 and UBC9, in addition to the canonical E2–E3 interaction; SUMO acts as a bridge with non-overlapping interfaces for UBC9 and PIAS1; phosphorylation of serine residues adjacent to the PIAS1 SIM favors this ternary complex; the ternary complex is required for PIAS1/SUMO1-mediated transcriptional repression.","method":"Bioluminescence resonance energy transfer (BRET), NMR spectroscopy, isothermal titration calorimetry, biochemical binding assays, functional transcriptional repression assays","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — NMR plus ITC plus BRET plus functional transcription assay, multiple rigorous biophysical methods, single lab","pmids":["24174529"],"is_preprint":false},{"year":2013,"finding":"PIAS1 is a component of the transcription-coupled DNA damage repair complex containing PNKP (polynucleotide kinase-phosphatase) and functions as a SUMO E3 ligase for PNKP; PIAS1 knockdown restores mutant HTT-perturbed PNKP enzymatic activity.","method":"Co-immunoprecipitation of repair complex, SUMOylation assay for PNKP, PNKP activity assay after PIAS1 knockdown","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — Co-IP plus sumoylation assay plus enzymatic activity readout, single lab","pmids":["33468657"],"is_preprint":false},{"year":2014,"finding":"PIAS1 SUMOylates RUNX family members (RUNX1, RUNX2, RUNX3) at a conserved lysine residue; PIAS1-mediated sumoylation inhibits RUNX3 transactivation activity; this modification is promoted by AKT1 kinase; in nude mice, a RUNX3 sumoylation-site mutant promotes tumorigenicity compared to wild-type RUNX3.","method":"Drosophila genetic screen, cell-based sumoylation assays, mutagenesis, reporter assays, in vivo xenograft tumor model","journal":"Oncogenesis","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic screen plus sumoylation assay plus in vivo xenograft, multiple methods but single lab","pmids":["24777122"],"is_preprint":false},{"year":2014,"finding":"PIAS1 sumoylates CREB1Δ (short isoform) at Lys-271 and Lys-290, increasing CREB1Δ protein levels; CREB sumoylation in rat CA1 neurons is increased by water maze training; lentiviral transduction of sumoylation-deficient CREB (K271R/K290R) into CA1 impairs spatial memory, while PIAS1 siRNA knockdown in CA1 decreases endogenous CREB sumoylation and impairs spatial memory.","method":"In vitro and in vivo sumoylation assays, mutagenesis, lentiviral gene transfer, in vivo water maze, ChIP for BDNF promoter","journal":"The Journal of neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro sumoylation assay plus in vivo behavioral assay with viral knockdown and mutant, single lab","pmids":["25031400"],"is_preprint":false},{"year":2014,"finding":"PIAS1 functions as a chromatin-bound AR coregulator on prostate cancer cell chromatin; ChIP-seq shows PIAS1 occupies AR chromatin binding sites enriched with SUMO2/3 and H3K4me2; androgen exposure increases PIAS1 chromatin occupancy to overlap nearly completely with AR; PIAS1 also interacts with the pioneer factor FOXA1; PIAS1 depletion affects AR chromatin occupancy at sites enriched for HOXD13 and GATA motifs.","method":"ChIP-seq, RNAi, transcriptome analysis, coimmunoprecipitation","journal":"Nucleic acids research","confidence":"High","confidence_rationale":"Tier 2 / Moderate — genome-wide ChIP-seq plus RNAi plus transcriptome, multiple orthogonal methods, single lab","pmids":["25552417"],"is_preprint":false},{"year":2014,"finding":"PIAS1 promotes lymphomagenesis by SUMOylating MYC; PIAS1-mediated SUMOylation promotes MYC phosphorylation at Ser62 and dephosphorylation at Thr58, reducing MYC turnover and increasing its transcriptional activity; Pias1-null mice display endothelial defects reminiscent of Myc-null mice.","method":"Coimmunoprecipitation, cell-based sumoylation assay, phosphorylation analysis, MYC stability/turnover assays, siRNA knockdown, Pias1-null mice","journal":"Cell reports","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — Co-IP plus sumoylation assay plus phosphorylation analysis plus KO phenotype, single lab","pmids":["27239040"],"is_preprint":false},{"year":2015,"finding":"PIAS1 is the SUMO E3 ligase that mediates c-Myc SUMOylation; PIAS1 knockdown reduces c-Myc SUMOylation and increases c-Myc transcriptional activity; SUMOylated c-Myc is subsequently ubiquitylated by RNF4 and degraded by the proteasome; 10 SUMO acceptor lysines on c-Myc were identified by mass spectrometry.","method":"siRNA knockdown, in vivo sumoylation assay, mass spectrometry, mutagenesis, ubiquitination assay, transcriptional activity assays","journal":"Cell cycle","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — MS identification plus siRNA plus functional transcription and stability assays, single lab multiple methods","pmids":["25895136"],"is_preprint":false},{"year":2015,"finding":"PIAS1-mediated sumoylation of TRF2 triggers its proteasomal degradation: TRF2 interacts with PIAS1 in mammalian cells and is sumoylated by PIAS1; SUMO-conjugated TRF2 is recognized by the STUbL RNF4, which ubiquitinates it; proteasome inhibition stabilizes SUMO-conjugated but not unmodified TRF2.","method":"Coimmunoprecipitation, in vivo sumoylation assay, ubiquitination assay, proteasome inhibitor experiments","journal":"FEBS letters","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — Co-IP plus sumoylation plus ubiquitination assay, single lab","pmids":["26450775"],"is_preprint":false},{"year":2015,"finding":"In fission yeast, the PIAS1 ortholog Pli1 is stabilized by Ulp1-mediated desumoylation; delocalized Ulp1 leads to SUMO chain modification of Pli1 and its subsequent proteasomal degradation via the STUbL/Cdc48-Ufd1-Npl4 pathway, causing profound SUMO pathway defects and centromere dysfunction.","method":"Genetic yeast mutants, protein stability assays, proteasome inhibitors, SUMOylation assays in fission yeast","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic model with mechanistic biochemistry in yeast ortholog, single lab","pmids":["26221037"],"is_preprint":false},{"year":2016,"finding":"PIAS1 reduction in mouse striatum via intrastriatal miRNA injection reduces mHTT accumulation, SUMO- and ubiquitin-modified protein accumulation, and improves behavioral phenotypes in R6/2 HD mice; conversely, PIAS1 overexpression exacerbates mHTT accumulation and phenotypes.","method":"In vivo miRNA knockdown in R6/2 mice, intrastriatal injection, behavioral testing, biochemical fractionation, histology","journal":"Neuron","confidence":"High","confidence_rationale":"Tier 2 / Moderate — in vivo gain and loss of function with defined behavioral and molecular phenotypes, single lab","pmids":["27146268"],"is_preprint":false},{"year":2016,"finding":"PIAS1 constitutively localizes at PML nuclear bodies in a SUMO interaction motif (SIM)-dependent manner requiring SUMOylated/sumoylation-competent PML; upon HSV-1 infection, PIAS1 is recruited to nuclear sites of viral genome entry in a SIM-dependent, PML-enhanced manner, promotes SUMO1 accumulation at those sites, and cooperatively restricts HSV-1 replication; the viral E3 ligase ICP0 antagonizes PIAS1 recruitment.","method":"Immunofluorescence localization, SIM mutant analysis, siRNA knockdown, viral replication assays, colocalization with viral genome sites","journal":"Journal of virology","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — direct localization experiments plus SIM mutagenesis plus functional viral restriction assay, single lab","pmids":["27099310"],"is_preprint":false},{"year":2016,"finding":"PIAS1 inhibits EBV lytic replication and is cleaved by caspases upon lytic triggers (BCR activation, chemical induction); caspase-mediated cleavage of PIAS1 abolishes its restriction activity; a cleavage-resistant PIAS1 mutant suppresses EBV replication; mechanistically, PIAS1 acts as an inhibitor of transcription factors required for lytic gene expression.","method":"PIAS1 knockdown/reconstitution, caspase inhibitor experiments, cleavage-resistant mutant, EBV lytic gene expression analysis","journal":"Cell reports","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — loss/gain of function plus caspase inhibition plus cleavage-resistant mutant, single lab","pmids":["29262325"],"is_preprint":false},{"year":2018,"finding":"PIAS1 and PIAS4 promote PCNA sumoylation at Lys-164 during normal cell cycle; PIAS1/PIAS4 double-deficient cells show >90% decrease in PCNA Lys-164 sumoylation and >90% decrease in error-free template switch DNA damage tolerance; the PCNA mutation is epistatic with PIAS1/PIAS4 mutation, indicating their action is through PCNA sumoylation.","method":"PIAS1/PIAS4 knockout DT40 and human TK6 cells, Ig gene conversion assay (template switch readout), PCNA sumoylation assay, epistasis with PCNA mutant, PCNA-SUMO1 chimera rescue","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — clean genetic epistasis plus biochemical sumoylation assay plus chimeric rescue, multiple orthogonal methods","pmids":["30487218"],"is_preprint":false},{"year":2018,"finding":"PIAS1 acts as a specific E3 SUMO ligase for PPARγ in cardiomyocytes; PIAS1-mediated PPARγ sumoylation represses NF-κB activity; PIAS1 deficiency aggravates ischemia/reperfusion injury-induced apoptosis and inflammation in cardiomyocytes via NF-κB pathway activation.","method":"Co-IP, in vivo sumoylation assay, siRNA knockdown, overexpression, apoptosis and inflammatory assays, mouse I/R model","journal":"BMC cell biology","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — Co-IP plus sumoylation assay plus functional in vivo model, single lab","pmids":["30419807"],"is_preprint":false},{"year":2019,"finding":"PIAS1 is modified by SUMO3, and SUMO3-modified PIAS1 mediates AR cytoplasmic translocation, ubiquitination by MDM2, and proteasomal degradation; the SUMO-acceptor Lys-117 on PIAS1 is essential for AR translocation; PIAS1/SUMO3 promotes interaction between sumoylated PIAS1 and AR Lys-386/Lys-845 to form a binary complex that recruits MDM2 for AR ubiquitination.","method":"Coimmunoprecipitation, sumoylation assay, PIAS1 mutagenesis, immunostaining for AR localization, ubiquitination assay, MDM2 interaction","journal":"Cell communication and signaling","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — Co-IP plus sumoylation/ubiquitination assays plus localization imaging plus mutagenesis, single lab","pmids":["31752909"],"is_preprint":false},{"year":2020,"finding":"PIAS1 sumoylates vimentin (VIM) at Lys-439 and Lys-445; VIM sumoylation is necessary for dynamic vimentin disassembly, and cells expressing non-SUMOylatable VIM show reduced cell migration; quantitative SUMO proteomics identified 62 putative PIAS1 substrates across diverse cellular pathways.","method":"Quantitative SUMO proteomics (SILAC-based), in vivo sumoylation assay, mutagenesis of VIM sumoylation sites, cell migration assays","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — quantitative proteomics plus in vivo sumoylation assay plus mutagenesis plus functional migration readout, single lab multiple methods","pmids":["32047143"],"is_preprint":false},{"year":2021,"finding":"PIAS1 promotes SUMOylation of the m6A reader YTHDF2 at Lys-281, Lys-571, and Lys-572; YTHDF2 lacking sumoylation shows reduced binding to EBV transcripts and reduced EBV mRNA decay; PIAS1 synergizes with wild-type but not sumoylation-deficient YTHDF2 to limit EBV lytic replication; PIAS1 also sumoylates YTHDF1 and YTHDF3.","method":"Coimmunoprecipitation, in vivo sumoylation assay, mutagenesis, RNA binding assays, viral replication assays","journal":"mBio","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — Co-IP plus sumoylation assay plus RNA binding plus functional viral assay, single lab","pmids":["38236021"],"is_preprint":false},{"year":2021,"finding":"SLX4IP recruits PIAS1 to the SLX4 complex and activates its E3 SUMO ligase activity; PIAS1 sumoylates the telomere protein RAP1, disrupting its interaction with TRF2 and facilitating RAP1 nucleocytoplasmic shuttling; cytosolic RAP1 then binds IKK, activating NF-κB and inducing Jagged-1/Notch signaling to institute the ALT telomere maintenance pathway.","method":"Coimmunoprecipitation, SUMOylation assay, RAP1 localization tracking, NF-κB reporter assays, ALT assays","journal":"Science signaling","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — Co-IP plus sumoylation assay plus localization plus functional pathway assays, single lab","pmids":["34187905"],"is_preprint":false},{"year":2022,"finding":"PIAS1 interacts with influenza A virus polymerase subunit PB2 and catalyzes robust PB2 sumoylation, reducing PB2 stability; PIAS1 SUMO E3 ligase activity is required to inhibit viral RNP complex activity; PIAS1 knockdown/knockout increases IAV growth and virulence in mice, while overexpression suppresses replication.","method":"Coimmunoprecipitation, siRNA knockdown, CRISPR/Cas9 knockout, overexpression, RNP activity assay, SUMO ligase-dead mutant (C351S, W372A), protein stability assay, in vivo mouse model","journal":"PLoS pathogens","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — multiple orthogonal methods including ligase-dead mutant, in vivo mouse model, CRISPR KO, RNP activity assay, single lab","pmids":["35377920"],"is_preprint":false},{"year":2014,"finding":"Necdin binds PIAS1 central conserved domains and suppresses PIAS1-dependent sumoylation of substrates STAT1 and PML; necdin promotes ubiquitin-proteasome-mediated degradation of PIAS1 specifically within the nuclear matrix.","method":"Coimmunoprecipitation, sumoylation assays, ubiquitination/proteasome assays, nuclear matrix fractionation, PIAS1 terminal deletion mutants","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — Co-IP plus sumoylation suppression assay plus degradation assay plus fractionation, single lab","pmids":["24911587"],"is_preprint":false},{"year":2013,"finding":"PIAS1 interacts with STI1 (stress-inducible phosphoprotein 1) through aa 450–480 of PIAS1 (mapped by surface plasmon resonance and yeast two-hybrid); PIAS1 overexpression promotes STI1 nuclear retention and co-directs STI1 and Hsp90 to specific sub-nuclear regions; PIAS1 can act as a SUMO E3 ligase for STI1 (5 sites identified by MS), but PIAS1-mediated nuclear retention of STI1 can occur through direct interaction even with non-sumoylatable STI1; PIAS1 knockdown impairs radiation-induced nuclear STI1 accumulation.","method":"Yeast two-hybrid, surface plasmon resonance, coimmunoprecipitation, mass spectrometry of SUMOylation sites, RNAi, subcellular fractionation/localization assays","journal":"Molecular & cellular proteomics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — SPR plus Co-IP plus MS plus RNAi plus localization, multiple methods single lab","pmids":["23938469"],"is_preprint":false},{"year":2020,"finding":"PIAS1 and TIF1γ form a trimeric complex with SnoN to collaboratively promote SnoN SUMOylation and suppress EMT; PIAS1 and TIF1γ act in an interdependent (not additive) manner for EMT suppression in breast organoids.","method":"Coimmunoprecipitation of trimeric complex, SUMOylation assay, loss-of-function (siRNA), 3D breast organoid EMT assay","journal":"Cell death and differentiation","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — Co-IP plus sumoylation assay plus functional organoid readout, single lab","pmids":["32770107"],"is_preprint":false}],"current_model":"PIAS1 is a SUMO E3 ligase that physically docks with activated STAT1 dimers (via its C-terminal domain recognizing the Stat1 N-terminal domain) and blocks their DNA binding, thereby selectively repressing IFN/cytokine-inducible gene transcription; it additionally sumoylates a broad spectrum of substrates—including p53, Sp3, androgen receptor, FAK, p73, PML, HTT, PCNA, vimentin, MYC, RUNX proteins, and viral factors—to regulate their activity, stability, or localization, and it is itself regulated by IKKα-mediated phosphorylation at Ser90 (required for NF-κB repression), PRMT1-mediated arginine methylation at Arg303 (required for late-phase STAT1 repression), and SUMO3-modification at Lys117 (required for AR degradation), while structurally its N-terminal SAP domain forms a four-helix bundle that binds A/T-rich DNA and mediates interactions with substrates and chromatin."},"narrative":{"mechanistic_narrative":"PIAS1 is a nuclear SUMO E3 ligase that controls gene expression and genome integrity by both catalytic SUMO conjugation of diverse substrates and non-enzymatic protein interactions, and it acts as a central negative regulator of inflammatory and innate-immune transcription [PMID:9724754, PMID:15311277, PMID:11583632]. Its founding activity is selective repression of cytokine-inducible transcription: PIAS1 docks onto activated, tyrosine-phosphorylated STAT1 dimers through its C-terminal domain binding the STAT1 N-terminal region and blocks STAT1 DNA binding, while in vivo a subset of IFN-inducible genes is derepressed in Pias1-null cells with increased STAT1 promoter recruitment [PMID:9724754, PMID:10805787, PMID:15311277]. In parallel it represses NF-κB by binding nuclear p65 and blocking its DNA binding [PMID:15657437]. As a RING-type SUMO E3 ligase, PIAS1 binds Ubc9 and SUMO and conjugates SUMO to a broad substrate spectrum—p53, Sp3, androgen receptor, FAK, p73, RUNX proteins, MYC, PML, vimentin, and PCNA—to control substrate activity, localization, or proteasomal turnover, often by priming substrates for STUbL (RNF4)-dependent degradation [PMID:11583632, PMID:12356736, PMID:12177000, PMID:27239040, PMID:25895136, PMID:26450775, PMID:30487218, PMID:32047143]. PIAS1 functions in DNA repair, being recruited via its SAP domain to double-strand breaks where it drives SUMO accumulation and the productive assembly of 53BP1, BRCA1, and RNF168, and it promotes PCNA Lys-164 sumoylation required for error-free template-switch damage tolerance [PMID:20016603, PMID:30487218]. Structurally, its N-terminal SAP domain forms a four-helix bundle that binds A/T-rich DNA and substrates, and PIAS1 forms a non-covalent ternary complex with SUMO1 and UBC9 required for transcriptional repression [PMID:15133049, PMID:24174529]. Its activity is tuned by post-translational modification—IKKα-mediated Ser90 phosphorylation enabling NF-κB repression and PRMT1-mediated Arg303 methylation enabling late-phase STAT1 repression [PMID:17540171, PMID:19136629]. PIAS1 additionally restricts viral replication (HSV-1, EBV, influenza A) and modulates Huntingtin sumoylation and aggregation in models of Huntington's disease [PMID:27099310, PMID:35377920, PMID:23871671, PMID:27146268].","teleology":[{"year":1998,"claim":"Established PIAS1's founding function by showing it selectively represses STAT1-dependent transcription, defining a paradigm of inhibitor of activated STAT.","evidence":"Co-IP, DNA binding and reporter assays in cytokine-stimulated cells","pmids":["9724754"],"confidence":"High","gaps":["Did not resolve the structural basis of the STAT1 interaction","Mechanism of selectivity for STAT1 over STAT2/3 unexplained"]},{"year":2000,"claim":"Mapped the interaction to PIAS1 C-terminus binding STAT1 N-terminus and showed PIAS1 selectively recognizes STAT1 dimers, explaining how repression is coupled to activation.","evidence":"Yeast two-hybrid, in vitro binding, domain deletion, dimer/monomer discrimination","pmids":["10805787"],"confidence":"High","gaps":["No structure of the PIAS1–STAT1 complex","How dimer recognition prevents DNA binding not shown at atomic level"]},{"year":2001,"claim":"Defined PIAS1 as a bona fide SUMO E3 ligase by reconstituting Ubc9-dependent p53 sumoylation and showing RING-domain dependence, transforming it from a STAT inhibitor into an enzyme.","evidence":"In vitro and cell-based SUMOylation assays with RING-domain mutagenesis","pmids":["11583632"],"confidence":"High","gaps":["Functional consequence of p53 sumoylation not fully resolved here","Substrate range unknown at the time"]},{"year":2002,"claim":"Extended the ligase function to transcription factors (Sp3, AR), establishing that PIAS1-mediated sumoylation silences transcriptional activity without altering DNA binding, and identified a RING-independent p53 coactivator role.","evidence":"In vitro/in vivo sumoylation, mutagenesis, reporter assays, Co-IP","pmids":["12356736","12177000","11788578"],"confidence":"High","gaps":["Whether sumoylation versus binding drives each transcriptional outcome not cleanly separated","Endogenous substrate-specificity determinants unmapped"]},{"year":2003,"claim":"Showed sumoylation can activate rather than silence a substrate, with FAK sumoylation at Lys-152 driving nuclear localization and autophosphorylation, broadening the functional outcomes of PIAS1 catalysis.","evidence":"Co-IP, in vitro binding, cell-based sumoylation, kinase assays, fractionation","pmids":["14500712"],"confidence":"High","gaps":["Physiological context of nuclear FAK function unclear","Downstream nuclear FAK targets not defined"]},{"year":2004,"claim":"Demonstrated PIAS1 is physiologically required to restrain innate immunity in vivo and resolved the SAP-domain four-helix-bundle structure that binds A/T-rich DNA, linking chromatin association to function.","evidence":"Pias1-/- mice, ChIP, gene expression; NMR structure with DNA/p53 binding assays","pmids":["15311277","15133049","15572666","15572677"],"confidence":"High","gaps":["How the SAP domain selects specific promoters in vivo not fully established","Genome-wide direct targets not defined at this stage"]},{"year":2005,"claim":"Generalized the transcriptional-repressor role beyond STAT1 to NF-κB p65 and revealed context-dependent coactivator functions (SRF-driven smooth muscle genes), establishing PIAS1 as a bidirectional transcriptional regulator.","evidence":"Pias1-/- mice, Co-IP, DNA binding, ChIP; mammalian two-hybrid and SRF-/- cells","pmids":["15657437","16135793","16144832"],"confidence":"High","gaps":["What dictates repressor versus coactivator behavior unclear","Promoter-context determinants of selectivity unresolved"]},{"year":2007,"claim":"Identified phosphorylation as the activating signal, with IKKα phosphorylating Ser90 to license NF-κB repression and promoter recruitment, integrating PIAS1 into proinflammatory signaling kinetics.","evidence":"Phospho-mutant analysis, Co-IP, ChIP in TNF/LPS-stimulated cells","pmids":["17540171","17440973"],"confidence":"High","gaps":["Structural effect of Ser90 phosphorylation unknown","Whether phosphorylation alters catalytic versus binding activity not separated"]},{"year":2009,"claim":"Showed arginine methylation at Arg303 by PRMT1 is required for late-phase STAT1 repression and defined PIAS1 recruitment to DSBs via its SAP domain, coupling it to SUMO-driven DNA repair factor assembly.","evidence":"In vitro methylation, MS, mutagenesis, ChIP; laser micro-irradiation, SAP mutants, epistasis","pmids":["19136629","20016603","19620279"],"confidence":"High","gaps":["How methylation and phosphorylation are coordinated unknown","Direct DSB-site SUMO substrates of PIAS1 not all defined"]},{"year":2010,"claim":"Linked PIAS1 to epigenetic gene silencing and lineage control by showing it maintains repressive chromatin at the Foxp3 promoter and modulates developmental signaling (Hedgehog/Gli, TGFβ/SnoN), expanding its role to chromatin and differentiation.","evidence":"Pias1-/- mice, ChIP, bisulfite sequencing; in vivo neural tube and EMT assays","pmids":["20966256","20711444","21103059","20421208"],"confidence":"High","gaps":["Direct versus indirect chromatin recruitment not fully separated","How DNMT/HP1 recruitment is targeted unresolved"]},{"year":2013,"claim":"Defined the SUMO–UBC9–PIAS1 ternary complex required for repression and connected PIAS1 to neurodegeneration by identifying it as the HTT SUMO ligase regulating insoluble HTT accumulation.","evidence":"NMR/ITC/BRET biophysics; E3 ligase screen, gain/loss-of-function, Drosophila HD model","pmids":["24174529","23871671","24061474","23938469"],"confidence":"High","gaps":["In vivo relevance of the ternary complex to specific substrates untested","Mechanism converting HTT sumoylation to insolubility unclear"]},{"year":2014,"claim":"Mapped PIAS1 genome-wide as a chromatin-bound AR coregulator and established it as the MYC/c-Myc SUMO ligase controlling MYC stability and oncogenic activity, embedding it in cancer-relevant transcription programs.","evidence":"ChIP-seq, RNAi, transcriptomics; Co-IP, sumoylation, MYC turnover/phospho analysis, MS","pmids":["25552417","27239040","25895136","24777122","25031400"],"confidence":"Medium","gaps":["Causal contribution of individual substrate sumoylations to tumorigenesis not isolated","Cooperation with FOXA1/pioneer factors mechanistically incomplete"]},{"year":2016,"claim":"Demonstrated in vivo therapeutic relevance in Huntington's disease, where striatal PIAS1 knockdown reduces mHTT accumulation and improves behavior, and showed PIAS1 restricts HSV-1 at PML nuclear bodies.","evidence":"In vivo miRNA knockdown in R6/2 mice; IF localization, SIM mutants, viral replication assays","pmids":["27146268","27099310","29262325","24911587"],"confidence":"High","gaps":["Substrate(s) mediating the HD benefit not pinned to a single target","How PML-body localization is regulated dynamically unclear"]},{"year":2018,"claim":"Established PIAS1 (with PIAS4) as the physiological SUMO ligase for PCNA Lys-164 required for error-free template-switch damage tolerance, giving it a defined genome-maintenance substrate by clean genetic epistasis.","evidence":"PIAS1/PIAS4 knockout cells, Ig conversion assay, PCNA sumoylation, epistasis, chimera rescue","pmids":["30487218"],"confidence":"High","gaps":["Relative substrate division of labor between PIAS1 and PIAS4 not resolved","Regulation of recruitment to replication-associated lesions unclear"]},{"year":2020,"claim":"Used quantitative SUMO proteomics to define a broad PIAS1 substrate landscape including vimentin, whose sumoylation regulates intermediate-filament dynamics and migration, framing PIAS1 as a global cytoskeletal and signaling SUMO regulator.","evidence":"SILAC SUMO proteomics, in vivo sumoylation, VIM site mutagenesis, migration assays; SnoN/TIF1γ organoid study","pmids":["32047143","32770107"],"confidence":"High","gaps":["Most of the 62 putative substrates lack functional validation","How substrate selectivity is achieved genome-wide unknown"]},{"year":2022,"claim":"Consolidated PIAS1 as a broad antiviral restriction factor by showing it sumoylates and destabilizes influenza A PB2 and the m6A reader YTHDF2 to limit IAV and EBV replication, with ligase activity required.","evidence":"Co-IP, CRISPR KO, ligase-dead mutants, RNP/stability assays, in vivo mouse IAV model","pmids":["35377920","38236021","34187905"],"confidence":"High","gaps":["Breadth of antiviral substrate targeting across virus families incomplete","How host SUMO machinery is mobilized during infection unresolved"]},{"year":null,"claim":"It remains unresolved how PIAS1 achieves substrate and promoter selectivity in vivo—how its post-translational modifications, SAP-domain DNA binding, and SIM-mediated localization are integrated to choose targets among its hundreds of potential substrates.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unifying model linking PIAS1 modification state to substrate choice","Structural basis of substrate discrimination beyond STAT1 unknown","Functional validation lacking for most proteomically identified substrates"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[2,3,4,6,43,46,49]},{"term_id":"GO:0016874","term_label":"ligase activity","supporting_discovery_ids":[2,3,43]},{"term_id":"GO:0003677","term_label":"DNA binding","supporting_discovery_ids":[8,24]},{"term_id":"GO:0140110","term_label":"transcription regulator activity","supporting_discovery_ids":[0,3,13,21]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[0,1,11,9]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[0,9,11,35]},{"term_id":"GO:0000228","term_label":"nuclear chromosome","supporting_discovery_ids":[20,43]}],"pathway":[{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[0,9,11]},{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[2,3,36,37,46]},{"term_id":"R-HSA-73894","term_label":"DNA Repair","supporting_discovery_ids":[20,43]},{"term_id":"R-HSA-74160","term_label":"Gene expression (Transcription)","supporting_discovery_ids":[0,13,21,35]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[29,40,41,49]}],"complexes":["PIAS1-SUMO1-UBC9 ternary complex","SLX4 complex (via SLX4IP)","CP2c/CP2b hexameric DNA-binding complex","PNKP transcription-coupled repair complex"],"partners":["STAT1","UBC9","RELA","TP53","IKBKA","PRMT1","FOXA1","PML"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"O75925","full_name":"E3 SUMO-protein ligase PIAS1","aliases":["DEAD/H box-binding protein 1","E3 SUMO-protein transferase PIAS1","Gu-binding protein","GBP","Protein inhibitor of activated STAT protein 1","RNA helicase II-binding protein"],"length_aa":651,"mass_kda":71.8,"function":"Functions as an E3-type small ubiquitin-like modifier (SUMO) ligase, stabilizing the interaction between UBE2I and the substrate, and as a SUMO-tethering factor (PubMed:11583632, PubMed:11867732, PubMed:14500712, PubMed:15280358, PubMed:21965678, PubMed:36050397). Catalyzes sumoylation of various proteins, such as CEBPB, MRE11, MTA1, PTK2, PML and ZNF76 (PubMed:11583632, PubMed:11867732, PubMed:14500712, PubMed:15280358, PubMed:21965678, PubMed:36050397). Plays a crucial role as a transcriptional coregulation in various cellular pathways, including the STAT pathway, the p53 pathway and the steroid hormone signaling pathway (PubMed:11583632, PubMed:11867732). In vitro, binds A/T-rich DNA (PubMed:15133049). The effects of this transcriptional coregulation, transactivation or silencing, may vary depending upon the biological context (PubMed:11583632, PubMed:11867732, PubMed:14500712, PubMed:21965678, PubMed:36050397). Mediates sumoylation of MRE11, stabilizing MRE11 on chromatin during end resection (PubMed:36050397). Sumoylates PML (at 'Lys-65' and 'Lys-160') and PML-RAR and promotes their ubiquitin-mediated degradation (By similarity). PIAS1-mediated sumoylation of PML promotes its interaction with CSNK2A1/CK2 which in turn promotes PML phosphorylation and degradation (By similarity). Enhances the sumoylation of MTA1 and may participate in its paralog-selective sumoylation (PubMed:21965678). Plays a dynamic role in adipogenesis by promoting the SUMOylation and degradation of CEBPB (By similarity). Mediates the nuclear mobility and localization of MSX1 to the nuclear periphery, whereby MSX1 is brought into the proximity of target myoblast differentiation factor genes (By similarity). Also required for the binding of MSX1 to the core enhancer region in target gene promoter regions, independent of its sumoylation activity (By similarity). Capable of binding to the core enhancer region TAAT box in the MYOD1 gene promoter (By similarity) (Microbial infection) Restricts Epstein-Barr virus (EBV) lytic replication by acting as an inhibitor for transcription factors involved in lytic gene expression (PubMed:29262325). The virus can use apoptotic caspases to antagonize PIAS1-mediated restriction and express its lytic genes (PubMed:29262325)","subcellular_location":"Nucleus; Nucleus speckle; Nucleus, PML body; Cytoplasm, cytoskeleton","url":"https://www.uniprot.org/uniprotkb/O75925/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/PIAS1","classification":"Not Classified","n_dependent_lines":248,"n_total_lines":1208,"dependency_fraction":0.2052980132450331},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"DDOST","stoichiometry":0.2},{"gene":"HSPA8","stoichiometry":0.2},{"gene":"OST4","stoichiometry":0.2},{"gene":"STT3B","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/PIAS1","total_profiled":1310},"omim":[{"mim_id":"617842","title":"PROTEASOME 26S SUBUNIT, NON-ATPase, 1; PSMD1","url":"https://www.omim.org/entry/617842"},{"mim_id":"617246","title":"NSE2 (MMS21) HOMOLOG, SMC5-SMC6 COMPLEX SUMO LIGASE; NSMCE2","url":"https://www.omim.org/entry/617246"},{"mim_id":"615708","title":"ZINC FINGER PROTEIN 451; ZNF451","url":"https://www.omim.org/entry/615708"},{"mim_id":"614162","title":"IMMUNODEFICIENCY 31C; IMD31C","url":"https://www.omim.org/entry/614162"},{"mim_id":"610650","title":"ADHESION-REGULATING MOLECULE 1; ADRM1","url":"https://www.omim.org/entry/610650"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Uncertain","locations":[{"location":"Nucleoplasm","reliability":"Uncertain"},{"location":"Cytosol","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/PIAS1"},"hgnc":{"alias_symbol":["GBP","GU/RH-II","ZMIZ3"],"prev_symbol":["DDXBP1"]},"alphafold":{"accession":"O75925","domains":[{"cath_id":"1.10.720.30","chopping":"1-65","consensus_level":"medium","plddt":89.0522,"start":1,"end":65},{"cath_id":"2.60.120.780","chopping":"143-233_245-288","consensus_level":"high","plddt":92.325,"start":143,"end":288},{"cath_id":"3.30.40.10","chopping":"293-414","consensus_level":"high","plddt":95.4785,"start":293,"end":414}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/O75925","model_url":"https://alphafold.ebi.ac.uk/files/AF-O75925-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-O75925-F1-predicted_aligned_error_v6.png","plddt_mean":68.31},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=PIAS1","jax_strain_url":"https://www.jax.org/strain/search?query=PIAS1"},"sequence":{"accession":"O75925","fasta_url":"https://rest.uniprot.org/uniprotkb/O75925.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/O75925/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/O75925"}},"corpus_meta":[{"pmid":"9724754","id":"PMC_9724754","title":"Inhibition of Stat1-mediated gene activation by PIAS1.","date":"1998","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/9724754","citation_count":586,"is_preprint":false},{"pmid":"20016603","id":"PMC_20016603","title":"Mammalian SUMO E3-ligases PIAS1 and PIAS4 promote responses to DNA double-strand breaks.","date":"2009","source":"Nature","url":"https://pubmed.ncbi.nlm.nih.gov/20016603","citation_count":441,"is_preprint":false},{"pmid":"11583632","id":"PMC_11583632","title":"Involvement of PIAS1 in the sumoylation of tumor suppressor p53.","date":"2001","source":"Molecular cell","url":"https://pubmed.ncbi.nlm.nih.gov/11583632","citation_count":408,"is_preprint":false},{"pmid":"12356736","id":"PMC_12356736","title":"Transcription factor Sp3 is silenced through SUMO modification by PIAS1.","date":"2002","source":"The EMBO 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gastroenterologie","url":"https://pubmed.ncbi.nlm.nih.gov/23472246","citation_count":14,"is_preprint":false},{"pmid":"26450775","id":"PMC_26450775","title":"PIAS1-mediated sumoylation promotes STUbL-dependent proteasomal degradation of the human telomeric protein TRF2.","date":"2015","source":"FEBS letters","url":"https://pubmed.ncbi.nlm.nih.gov/26450775","citation_count":14,"is_preprint":false},{"pmid":"17934332","id":"PMC_17934332","title":"PIAS1 interacts with the KRAB zinc finger protein, ZNF133, via zinc finger motifs and regulates its transcriptional activity.","date":"2007","source":"Experimental & molecular medicine","url":"https://pubmed.ncbi.nlm.nih.gov/17934332","citation_count":14,"is_preprint":false},{"pmid":"24872413","id":"PMC_24872413","title":"High mobility group nucleosomal binding domain 2 (HMGN2) SUMOylation by the SUMO E3 ligase PIAS1 decreases the binding affinity to nucleosome core particles.","date":"2014","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/24872413","citation_count":14,"is_preprint":false},{"pmid":"32770107","id":"PMC_32770107","title":"PIAS1 and TIF1γ collaborate to promote SnoN SUMOylation and suppression of epithelial-mesenchymal transition.","date":"2020","source":"Cell death and differentiation","url":"https://pubmed.ncbi.nlm.nih.gov/32770107","citation_count":13,"is_preprint":false},{"pmid":"27032383","id":"PMC_27032383","title":"PIAS1 binds p300 and behaves as a coactivator or corepressor of the transcription factor c-Myb dependent on SUMO-status.","date":"2016","source":"Biochimica et biophysica acta","url":"https://pubmed.ncbi.nlm.nih.gov/27032383","citation_count":13,"is_preprint":false},{"pmid":"20818504","id":"PMC_20818504","title":"SiRNA-mediated PIAS1 silencing promotes inflammatory response and leads to injury of cerulein-stimulated pancreatic acinar cells via regulation of the P38MAPK signaling pathway.","date":"2010","source":"International journal of molecular medicine","url":"https://pubmed.ncbi.nlm.nih.gov/20818504","citation_count":13,"is_preprint":false},{"pmid":"32688147","id":"PMC_32688147","title":"SUMO E3 ligase PIAS1 is a potential biomarker indicating stress susceptibility.","date":"2020","source":"Psychoneuroendocrinology","url":"https://pubmed.ncbi.nlm.nih.gov/32688147","citation_count":12,"is_preprint":false},{"pmid":"34195189","id":"PMC_34195189","title":"The E3 Ligase PIAS1 Regulates p53 Sumoylation to Control Stress-Induced Apoptosis of Lens Epithelial Cells Through the Proapoptotic Regulator Bax.","date":"2021","source":"Frontiers in cell and developmental biology","url":"https://pubmed.ncbi.nlm.nih.gov/34195189","citation_count":12,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":51125,"output_tokens":13495,"usd":0.1779,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":25192,"output_tokens":5751,"usd":0.134868,"stage2_stop_reason":"end_turn"},"total_usd":0.312768,"stage1_batch_id":"msgbatch_01CNoDbkChHEkgrJnL7BwtGJ","stage2_batch_id":"msgbatch_016Y4x9E9Wg5VQDANj9quSQD","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1998,\n      \"finding\": \"PIAS1 specifically inhibits STAT1-mediated gene activation by blocking the DNA binding activity of Stat1; PIAS1 physically associates with Stat1 (but not Stat2 or Stat3) after cytokine stimulation, and this interaction requires Stat1 phosphorylation on Tyr-701.\",\n      \"method\": \"Coimmunoprecipitation, DNA binding assays, reporter gene assays, yeast two-hybrid\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP, DNA binding assay, reporter assay, replicated across multiple labs subsequently\",\n      \"pmids\": [\"9724754\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"The COOH-terminal domain of PIAS1 (aa 392–541) directly interacts with the NH2-terminal domain of Stat1 (aa 1–191), and PIAS1 specifically recognizes the dimeric form of Stat1 rather than the monomer; the NH2-terminal region of PIAS1 acts as a modulatory domain preventing interaction with Stat1 monomers.\",\n      \"method\": \"Yeast two-hybrid, in vitro binding assays, domain deletion mutants, modified yeast two-hybrid for dimer vs. monomer discrimination\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — in vitro direct binding plus yeast two-hybrid with domain mapping, single lab but multiple orthogonal methods\",\n      \"pmids\": [\"10805787\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"PIAS1 functions as a SUMO E3 ligase for p53: it binds SUMO-1 and Ubc9 (the E2), catalyzes p53 sumoylation in vitro and in cells, and a RING finger-like domain mutation abolishes Ubc9 binding and ligase activity while retaining p53/SUMO-1 binding.\",\n      \"method\": \"Yeast two-hybrid, in vitro SUMOylation assay, cell-based SUMOylation assay, RING domain mutagenesis\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution of E3 activity, active-site mutagenesis, replicated in multiple subsequent studies\",\n      \"pmids\": [\"11583632\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"PIAS1 acts as a SUMO E3 ligase for the transcription factor Sp3, stimulating SUMO conjugation at a single lysine in the IKXE motif; PIAS1 interacts with both Sp3 and Ubc9, and SUMO modification of Sp3 silences its transcriptional activity without altering DNA-binding specificity or affinity.\",\n      \"method\": \"In vitro and in vivo SUMOylation assays, mutagenesis, GST pulldown, reporter assays\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution plus mutagenesis plus functional transcription assays, single lab multiple orthogonal methods\",\n      \"pmids\": [\"12356736\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"PIAS1 (and PIASxα) act as SUMO E3 ligases for the androgen receptor (AR), enhancing AR sumoylation in an RING finger-like domain-dependent manner; ligand (testosterone) binding to AR is required for sumoylation in intact cells, and PIAS1-mediated sumoylation represses AR-dependent transcription.\",\n      \"method\": \"Cell-based and in vitro SUMOylation assays, RING domain mutagenesis, reporter gene assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution plus active-site mutagenesis plus functional transcription assays, single lab\",\n      \"pmids\": [\"12177000\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"PIAS1 activates p53-mediated transcription independently of its RING finger (sumoylation) domain; PIAS1 interacts with the tetramerization and C-terminal regulatory domains of p53, and endogenous PIAS1 co-immunoprecipitates with endogenous p53.\",\n      \"method\": \"Yeast two-hybrid, coimmunoprecipitation, reporter gene assays, RING domain deletion mutant\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — Co-IP plus reporter assay plus domain mutants, single lab\",\n      \"pmids\": [\"11788578\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"PIAS1 interacts with and sumoylates focal adhesion kinase (FAK) at Lys-152; sumoylation promotes FAK nuclear localization and dramatically increases FAK autophosphorylation at Tyr-397 in intact cells and in kinase assays, independently of cell adhesion.\",\n      \"method\": \"Yeast two-hybrid, in vitro binding, coimmunoprecipitation, cell-based SUMOylation, kinase assays, mutagenesis, subcellular fractionation\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — multiple orthogonal methods including in vitro assay, kinase assay, mutagenesis, fractionation, single lab\",\n      \"pmids\": [\"14500712\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"PIAS1 sumoylates p73α (but not C-terminally truncated isoforms p73β and p73γ) through its RING finger domain; PIAS1 binding stabilizes p73, sumoylated p73 is restricted to the nuclear matrix, PIAS1-mediated sumoylation decreases p73 transcriptional activity, and PIAS1 overexpression reduces cells in G1 via reduced p21 transcription whereas PIAS1 siRNA causes G2 arrest.\",\n      \"method\": \"Yeast two-hybrid, pulldown, coimmunoprecipitation, cell-based SUMOylation, reporter assays, RNAi, cell cycle analysis\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — multiple orthogonal methods (CoIP, sumoylation assay, RNAi, functional reporter, cell cycle), single lab\",\n      \"pmids\": [\"15572666\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"NMR structure of the N-terminal domain (residues 1–65) of PIAS1 revealed a four-helix SAP domain; this domain binds p53 (GST pulldown) and has strong affinity toward A/T-rich DNA, with the binding site mapping to one end of the four-helix bundle fitting the minor groove.\",\n      \"method\": \"NMR spectroscopy, GST pulldown, gel mobility shift assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — structure determined by NMR with biochemical binding validation, single lab\",\n      \"pmids\": [\"15133049\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"PIAS1 is required for the innate immune response in vivo: Pias1−/− cells show that PIAS1 selectively inhibits a subset of IFN-γ– or IFN-β–inducible genes by interfering with STAT1 recruitment to gene promoters; Pias1−/− mice exhibit enhanced antiviral activity and increased protection against pathogenic infection.\",\n      \"method\": \"Knockout mouse (Pias1−/−), chromatin immunoprecipitation, gene expression analysis\",\n      \"journal\": \"Nature immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean KO with defined cellular phenotype plus ChIP mechanism, replicated in vivo\",\n      \"pmids\": [\"15311277\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"SNM1A physically interacts with PIAS1 and they colocalize at nuclear foci; point mutations in the SNM1 domain that disrupt PIAS1 interaction cause mislocalization of SNM1A and loss of complementation of ICL repair defects, demonstrating PIAS1 interaction is required for SNM1A-mediated DNA interstrand cross-link repair.\",\n      \"method\": \"Coimmunoprecipitation, colocalization, mutagenesis, genetic complementation in DT40 cells\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus colocalization plus mutagenesis plus genetic complementation, single lab\",\n      \"pmids\": [\"15572677\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"PIAS1 negatively regulates NF-κB signaling: upon cytokine stimulation, the p65 subunit of NF-κB translocates to the nucleus where it interacts with PIAS1; PIAS1 blocks p65 DNA binding activity in vitro and in vivo, and Pias1−/− cells show increased p65 occupancy at NF-κB target gene promoters.\",\n      \"method\": \"Knockout mouse, coimmunoprecipitation, in vitro DNA binding assay, chromatin immunoprecipitation, microarray\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — KO mouse plus Co-IP plus in vitro and in vivo DNA binding assays, multiple orthogonal methods\",\n      \"pmids\": [\"15657437\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"PIAS1 interacts with and sumoylates metabotropic glutamate receptor 8 (mGluR8) C-terminal domain; PIAS1 binding requires a region N-terminal to the consensus sumoylation motif and sumoylation occurs at Lys-882 within that motif in HEK293 cells.\",\n      \"method\": \"Yeast two-hybrid, GST pulldown, cell-based SUMOylation, mutagenesis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — yeast two-hybrid confirmed by GST pulldown and in-cell sumoylation with mutagenesis, single lab\",\n      \"pmids\": [\"16144832\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"PIAS1 activates smooth muscle cell differentiation marker genes (SM α-actin, SM MHC, SM22α) by interacting with serum response factor (SRF) and class I bHLH proteins (E2-2, E12); PIAS1 is required for SRF binding to the SM α-actin promoter in intact chromatin, and its effect requires SRF.\",\n      \"method\": \"Yeast two-hybrid, mammalian two-hybrid, coimmunoprecipitation, reporter assays, RNAi, chromatin immunoprecipitation, SRF−/− embryonic stem cells\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (CoIP, ChIP, KO cells, RNAi) in single lab\",\n      \"pmids\": [\"16135793\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"PIAS1 confers DNA-binding specificity on the Msx1 homeoprotein by regulating its subnuclear localization to the nuclear periphery; interaction with PIAS1 (not sumoylation per se) is required for Msx1 to repress myogenic genes (MyoD, Myf5) and inhibit myoblast differentiation; myogenic regulatory genes repressed by Msx1 also localize at the nuclear periphery.\",\n      \"method\": \"Coimmunoprecipitation, live imaging, subnuclear localization assays, mutagenesis, reporter assays, RNAi\",\n      \"journal\": \"Genes & development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus direct localization experiment plus RNAi functional assay, multiple orthogonal methods single lab\",\n      \"pmids\": [\"16600910\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Proinflammatory stimuli (TNF, LPS) induce IKKα-mediated phosphorylation of PIAS1 at Ser90; this phosphorylation is required for PIAS1 to repress NF-κB target gene transcription and for its rapid recruitment to NF-κB target gene promoters; IKKα (but not IKKβ) interacts with PIAS1 in vivo and mediates this phosphorylation in a SUMO ligase-dependent manner.\",\n      \"method\": \"Phospho-specific mutants (Ser90A), coimmunoprecipitation, chromatin immunoprecipitation, in vivo interaction assays\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — phosphomutant analysis plus Co-IP plus ChIP, single lab but multiple orthogonal methods in high-impact study\",\n      \"pmids\": [\"17540171\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"PIAS1 interacts with and represses SOX9 transcriptional activity; PIAS1 enhances SUMOylation of SOX9 at Lys-396, and sumoylated SOX9 has reduced transcriptional activity on reporter constructs; PIAS1 can also repress SUMOylation-deficient SOX9-K396R, indicating additional SUMO ligase-dependent mechanisms.\",\n      \"method\": \"GST pulldown, coimmunoprecipitation, colocalization in tissue culture and mouse embryos, reporter assays, mutagenesis\",\n      \"journal\": \"Molecular reproduction and development\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — pulldown plus Co-IP plus reporter assay plus mutagenesis, single lab\",\n      \"pmids\": [\"17440973\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"PIAS1 and GATA-3 interact in Th2 cells; PIAS1 functions as a positive transcriptional coregulator for GATA-3 and facilitates GATA-3 recruitment to the IL-13 promoter, enhancing IL-13 expression in a promoter-selective manner.\",\n      \"method\": \"Coimmunoprecipitation, ChIP, reporter assays, siRNA knockdown, gain-of-function overexpression\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — Co-IP plus ChIP plus functional reporter and siRNA, single lab\",\n      \"pmids\": [\"18056374\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"PRMT1 arginine-methylates PIAS1 at Arg-303 in vitro and in vivo upon IFN treatment; methylation-deficient and methylation-mimicking mutants show that this modification is essential for PIAS1 to be recruited to STAT1 target gene promoters in the late IFN response phase, leading to STAT1 release and transcriptional repression.\",\n      \"method\": \"In vitro methylation assay, mass spectrometry of methylation sites, mutagenesis, chromatin immunoprecipitation, RNAi\",\n      \"journal\": \"Genes & development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — in vitro biochemical assay plus mass spectrometry plus mutagenesis plus ChIP, single lab multiple orthogonal methods\",\n      \"pmids\": [\"19136629\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"SOCS1, SOCS3, and PIAS1 each promote myogenic differentiation by inhibiting the LIF-induced JAK1/STAT1/STAT3 pathway via distinct targets; PIAS1 targets activated STAT1 and prevents its DNA binding; the SUMO E3 ligase activity of PIAS1 is dispensable for its role in myogenic differentiation.\",\n      \"method\": \"Reporter assays, RNAi knockdown, overexpression, DNA binding assays, SUMO ligase-dead mutant analysis\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — RNAi plus overexpression plus ligase-dead mutant plus DNA binding assay, single lab\",\n      \"pmids\": [\"19620279\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"PIAS1 and PIAS4 are recruited to DNA double-strand break sites via their SAP domains and are required for SUMO1 and SUMO2/3 accumulation at DSB sites; they promote the productive association of 53BP1, BRCA1, and RNF168 with damage sites and are required for ubiquitin adduct formation by RNF8, RNF168, and BRCA1, ultimately promoting DSB repair and conferring ionizing radiation resistance.\",\n      \"method\": \"Laser micro-irradiation/IRIF assays, SAP domain mutants, siRNA knockdown, epistasis with E3 ligases, repair assays\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (IRIF, domain mutants, siRNA, functional epistasis), high-impact journal, subsequently replicated\",\n      \"pmids\": [\"20016603\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"PIAS1 restricts natural T regulatory (Treg) cell differentiation by maintaining repressive chromatin at the Foxp3 promoter; PIAS1 binds the Foxp3 promoter and recruits DNA methyltransferases and heterochromatin protein 1 (HP1) for epigenetic modifications; Pias1 deletion causes promoter demethylation, reduced H3K9 methylation, and increased Treg numbers in vivo.\",\n      \"method\": \"Knockout mouse, ChIP, bisulfite sequencing, chromatin accessibility assays, flow cytometry\",\n      \"journal\": \"Science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean KO mouse plus ChIP plus epigenetic profiling, multiple orthogonal methods\",\n      \"pmids\": [\"20966256\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"PIAS1 suppresses TGFβ-induced EMT in mammary epithelial cells in a SUMO ligase-dependent manner; TGFβ downregulates PIAS1 levels during EMT; PIAS1 sumoylates SnoN, and loss of SnoN sumoylation impairs its ability to inhibit TGFβ-induced EMT.\",\n      \"method\": \"Gain/loss-of-function (overexpression and siRNA), sumoylation assays, mutagenesis of SnoN sumoylation sites, morphological EMT readouts\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — gain/loss of function plus sumoylation assay plus mutagenesis, single lab\",\n      \"pmids\": [\"21103059\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"PIAS1 promotes sumoylation of the Gli transcription factors downstream of Hedgehog signaling; expression of SUMO-1 or PIAS1 increases Gli transcriptional activity in vitro; in the embryonic neural tube, forced PIAS1 expression increases Gli activity and induces ectopic Nkx2.2, while a ligase-dead PIAS1 mutant blocks endogenous Nkx2.2 expression.\",\n      \"method\": \"Cell-based SUMOylation assays, reporter assays, in ovo electroporation in embryonic neural tube, PIAS1 ligase-dead mutant\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro and in vivo (neural tube) functional assays with ligase-dead mutant control, single lab\",\n      \"pmids\": [\"20711444\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"PIAS1 regulates subnuclear localization of CP2c and forms a stable hexameric DNA-binding complex with CP2c and CP2b on the α-globin promoter; PIAS1 acts as a SUMO-independent co-activator by bridging two CP2 proteins through distinct interaction domains; PIAS1 knockdown reduces both CP2c and CP2b promoter occupancy.\",\n      \"method\": \"RNAi knockdown, in vitro DNA binding (EMSA), coimmunoprecipitation, ChIP, nuclear localization assays, domain mapping\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — in vitro complex reconstitution plus ChIP plus RNAi, single lab\",\n      \"pmids\": [\"20421208\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"PIAS1 couples ROS-dependent JNK activation to the SUMO pathway: PIAS1 knockdown prevents ROS-induced hypersumoylation and also enhances JNK signaling; conversely, PIAS1 overexpression inhibits JNK activity independently of its SUMO ligase function, indicating a non-enzymatic function in JNK regulation; PIAS1 knockdown attenuates ROS-dependent apoptosis.\",\n      \"method\": \"siRNA knockdown, overexpression, JNK activity assays, SUMO ligase-dead mutants, caspase-3/7 activity assays, transcriptomic profiling\",\n      \"journal\": \"FASEB journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — RNAi plus overexpression plus ligase-dead mutant, single lab\",\n      \"pmids\": [\"21676946\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"PIAS1 sumoylates PML to promote its CK2-mediated phosphorylation and subsequent ubiquitin/proteasome-mediated degradation, attenuating PML tumor suppressor function; PIAS1-mediated sumoylation of PML-RARA is essential for arsenic trioxide-induced degradation of PML-RARA and apoptosis in APL cells.\",\n      \"method\": \"Co-IP, SUMOylation assays, proteasome inhibitor studies, siRNA knockdown, apoptosis assays\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — Co-IP plus sumoylation assay plus functional rescue, single lab\",\n      \"pmids\": [\"22406621\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"PIAS1 sumoylates SATB1 at Lys-744, and this sumoylation regulates caspase-6-mediated cleavage of SATB1 at PML nuclear bodies; phosphorylation of SATB1 at Thr-188 inhibits its interaction with the PIAS1 SAP motif and thereby blocks sumoylation; an LXXLL motif (residues 193–197) near the phosphorylation site mediates interaction with the PIAS SAP domain.\",\n      \"method\": \"Mutagenesis, coimmunoprecipitation, in vitro binding, cell-based sumoylation and cleavage assays\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — mutagenesis plus in vitro binding plus functional cleavage assay, single lab\",\n      \"pmids\": [\"20351170\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"PIAS1 is phosphorylated at Ser522 by MAPK-activated protein kinase-2 (MK2); this phosphorylation enhances both PIAS1 SUMO E3 ligase activity (toward p53) and its transrepression activity; PIAS1-S522A mutant fails to promote p53 sumoylation or exert anti-inflammatory effects in endothelial cells in vitro and in vivo.\",\n      \"method\": \"Phosphomutant analysis (S522A), in vivo p53 sumoylation assay, reporter assays, leukocyte rolling in microvessels (in vivo)\",\n      \"journal\": \"Arteriosclerosis, thrombosis, and vascular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — phosphomutant plus in vivo sumoylation plus functional in vitro and in vivo readouts, single lab\",\n      \"pmids\": [\"23202365\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"PIAS1 is an E3 SUMO ligase for both Huntingtin (HTT) SUMO-1 and SUMO-2 modification; PIAS1-mediated SUMO-2 modification regulates the accumulation of insoluble HTT; overexpression of PIAS1 increases and knockdown decreases insoluble HTT accumulation; reduction of dPIAS in a mutant HTT Drosophila model is protective.\",\n      \"method\": \"Systematic E3 SUMO ligase screen, siRNA knockdown, overexpression, insolubility fractionation assays, Drosophila model\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — systematic screen plus gain/loss of function plus Drosophila in vivo validation, multiple orthogonal methods\",\n      \"pmids\": [\"23871671\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"PIAS1 functions as a SUMO E3 ligase for C/EBPβ through its SAP domain interaction; PIAS1-mediated sumoylation of C/EBPβ promotes its ubiquitination and proteasomal degradation; PIAS1 expression transiently peaks on day 4 of adipocyte differentiation when C/EBPβ declines, and PIAS1 inhibits adipogenesis in a catalytic activity-dependent manner.\",\n      \"method\": \"Coimmunoprecipitation, in vitro and in vivo sumoylation assays, ubiquitination assays, protein stability assays, RNAi, overexpression, adipogenesis assays\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — in vitro and in vivo sumoylation assay plus ubiquitination/stability assay plus functional differentiation rescue, single lab multiple orthogonal methods\",\n      \"pmids\": [\"24061474\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"PIAS1 forms a non-covalent ternary complex with SUMO1 and UBC9, in addition to the canonical E2–E3 interaction; SUMO acts as a bridge with non-overlapping interfaces for UBC9 and PIAS1; phosphorylation of serine residues adjacent to the PIAS1 SIM favors this ternary complex; the ternary complex is required for PIAS1/SUMO1-mediated transcriptional repression.\",\n      \"method\": \"Bioluminescence resonance energy transfer (BRET), NMR spectroscopy, isothermal titration calorimetry, biochemical binding assays, functional transcriptional repression assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — NMR plus ITC plus BRET plus functional transcription assay, multiple rigorous biophysical methods, single lab\",\n      \"pmids\": [\"24174529\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"PIAS1 is a component of the transcription-coupled DNA damage repair complex containing PNKP (polynucleotide kinase-phosphatase) and functions as a SUMO E3 ligase for PNKP; PIAS1 knockdown restores mutant HTT-perturbed PNKP enzymatic activity.\",\n      \"method\": \"Co-immunoprecipitation of repair complex, SUMOylation assay for PNKP, PNKP activity assay after PIAS1 knockdown\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — Co-IP plus sumoylation assay plus enzymatic activity readout, single lab\",\n      \"pmids\": [\"33468657\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"PIAS1 SUMOylates RUNX family members (RUNX1, RUNX2, RUNX3) at a conserved lysine residue; PIAS1-mediated sumoylation inhibits RUNX3 transactivation activity; this modification is promoted by AKT1 kinase; in nude mice, a RUNX3 sumoylation-site mutant promotes tumorigenicity compared to wild-type RUNX3.\",\n      \"method\": \"Drosophila genetic screen, cell-based sumoylation assays, mutagenesis, reporter assays, in vivo xenograft tumor model\",\n      \"journal\": \"Oncogenesis\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic screen plus sumoylation assay plus in vivo xenograft, multiple methods but single lab\",\n      \"pmids\": [\"24777122\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"PIAS1 sumoylates CREB1Δ (short isoform) at Lys-271 and Lys-290, increasing CREB1Δ protein levels; CREB sumoylation in rat CA1 neurons is increased by water maze training; lentiviral transduction of sumoylation-deficient CREB (K271R/K290R) into CA1 impairs spatial memory, while PIAS1 siRNA knockdown in CA1 decreases endogenous CREB sumoylation and impairs spatial memory.\",\n      \"method\": \"In vitro and in vivo sumoylation assays, mutagenesis, lentiviral gene transfer, in vivo water maze, ChIP for BDNF promoter\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro sumoylation assay plus in vivo behavioral assay with viral knockdown and mutant, single lab\",\n      \"pmids\": [\"25031400\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"PIAS1 functions as a chromatin-bound AR coregulator on prostate cancer cell chromatin; ChIP-seq shows PIAS1 occupies AR chromatin binding sites enriched with SUMO2/3 and H3K4me2; androgen exposure increases PIAS1 chromatin occupancy to overlap nearly completely with AR; PIAS1 also interacts with the pioneer factor FOXA1; PIAS1 depletion affects AR chromatin occupancy at sites enriched for HOXD13 and GATA motifs.\",\n      \"method\": \"ChIP-seq, RNAi, transcriptome analysis, coimmunoprecipitation\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genome-wide ChIP-seq plus RNAi plus transcriptome, multiple orthogonal methods, single lab\",\n      \"pmids\": [\"25552417\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"PIAS1 promotes lymphomagenesis by SUMOylating MYC; PIAS1-mediated SUMOylation promotes MYC phosphorylation at Ser62 and dephosphorylation at Thr58, reducing MYC turnover and increasing its transcriptional activity; Pias1-null mice display endothelial defects reminiscent of Myc-null mice.\",\n      \"method\": \"Coimmunoprecipitation, cell-based sumoylation assay, phosphorylation analysis, MYC stability/turnover assays, siRNA knockdown, Pias1-null mice\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — Co-IP plus sumoylation assay plus phosphorylation analysis plus KO phenotype, single lab\",\n      \"pmids\": [\"27239040\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"PIAS1 is the SUMO E3 ligase that mediates c-Myc SUMOylation; PIAS1 knockdown reduces c-Myc SUMOylation and increases c-Myc transcriptional activity; SUMOylated c-Myc is subsequently ubiquitylated by RNF4 and degraded by the proteasome; 10 SUMO acceptor lysines on c-Myc were identified by mass spectrometry.\",\n      \"method\": \"siRNA knockdown, in vivo sumoylation assay, mass spectrometry, mutagenesis, ubiquitination assay, transcriptional activity assays\",\n      \"journal\": \"Cell cycle\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — MS identification plus siRNA plus functional transcription and stability assays, single lab multiple methods\",\n      \"pmids\": [\"25895136\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"PIAS1-mediated sumoylation of TRF2 triggers its proteasomal degradation: TRF2 interacts with PIAS1 in mammalian cells and is sumoylated by PIAS1; SUMO-conjugated TRF2 is recognized by the STUbL RNF4, which ubiquitinates it; proteasome inhibition stabilizes SUMO-conjugated but not unmodified TRF2.\",\n      \"method\": \"Coimmunoprecipitation, in vivo sumoylation assay, ubiquitination assay, proteasome inhibitor experiments\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — Co-IP plus sumoylation plus ubiquitination assay, single lab\",\n      \"pmids\": [\"26450775\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"In fission yeast, the PIAS1 ortholog Pli1 is stabilized by Ulp1-mediated desumoylation; delocalized Ulp1 leads to SUMO chain modification of Pli1 and its subsequent proteasomal degradation via the STUbL/Cdc48-Ufd1-Npl4 pathway, causing profound SUMO pathway defects and centromere dysfunction.\",\n      \"method\": \"Genetic yeast mutants, protein stability assays, proteasome inhibitors, SUMOylation assays in fission yeast\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic model with mechanistic biochemistry in yeast ortholog, single lab\",\n      \"pmids\": [\"26221037\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"PIAS1 reduction in mouse striatum via intrastriatal miRNA injection reduces mHTT accumulation, SUMO- and ubiquitin-modified protein accumulation, and improves behavioral phenotypes in R6/2 HD mice; conversely, PIAS1 overexpression exacerbates mHTT accumulation and phenotypes.\",\n      \"method\": \"In vivo miRNA knockdown in R6/2 mice, intrastriatal injection, behavioral testing, biochemical fractionation, histology\",\n      \"journal\": \"Neuron\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo gain and loss of function with defined behavioral and molecular phenotypes, single lab\",\n      \"pmids\": [\"27146268\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"PIAS1 constitutively localizes at PML nuclear bodies in a SUMO interaction motif (SIM)-dependent manner requiring SUMOylated/sumoylation-competent PML; upon HSV-1 infection, PIAS1 is recruited to nuclear sites of viral genome entry in a SIM-dependent, PML-enhanced manner, promotes SUMO1 accumulation at those sites, and cooperatively restricts HSV-1 replication; the viral E3 ligase ICP0 antagonizes PIAS1 recruitment.\",\n      \"method\": \"Immunofluorescence localization, SIM mutant analysis, siRNA knockdown, viral replication assays, colocalization with viral genome sites\",\n      \"journal\": \"Journal of virology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — direct localization experiments plus SIM mutagenesis plus functional viral restriction assay, single lab\",\n      \"pmids\": [\"27099310\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"PIAS1 inhibits EBV lytic replication and is cleaved by caspases upon lytic triggers (BCR activation, chemical induction); caspase-mediated cleavage of PIAS1 abolishes its restriction activity; a cleavage-resistant PIAS1 mutant suppresses EBV replication; mechanistically, PIAS1 acts as an inhibitor of transcription factors required for lytic gene expression.\",\n      \"method\": \"PIAS1 knockdown/reconstitution, caspase inhibitor experiments, cleavage-resistant mutant, EBV lytic gene expression analysis\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — loss/gain of function plus caspase inhibition plus cleavage-resistant mutant, single lab\",\n      \"pmids\": [\"29262325\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"PIAS1 and PIAS4 promote PCNA sumoylation at Lys-164 during normal cell cycle; PIAS1/PIAS4 double-deficient cells show >90% decrease in PCNA Lys-164 sumoylation and >90% decrease in error-free template switch DNA damage tolerance; the PCNA mutation is epistatic with PIAS1/PIAS4 mutation, indicating their action is through PCNA sumoylation.\",\n      \"method\": \"PIAS1/PIAS4 knockout DT40 and human TK6 cells, Ig gene conversion assay (template switch readout), PCNA sumoylation assay, epistasis with PCNA mutant, PCNA-SUMO1 chimera rescue\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — clean genetic epistasis plus biochemical sumoylation assay plus chimeric rescue, multiple orthogonal methods\",\n      \"pmids\": [\"30487218\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"PIAS1 acts as a specific E3 SUMO ligase for PPARγ in cardiomyocytes; PIAS1-mediated PPARγ sumoylation represses NF-κB activity; PIAS1 deficiency aggravates ischemia/reperfusion injury-induced apoptosis and inflammation in cardiomyocytes via NF-κB pathway activation.\",\n      \"method\": \"Co-IP, in vivo sumoylation assay, siRNA knockdown, overexpression, apoptosis and inflammatory assays, mouse I/R model\",\n      \"journal\": \"BMC cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — Co-IP plus sumoylation assay plus functional in vivo model, single lab\",\n      \"pmids\": [\"30419807\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"PIAS1 is modified by SUMO3, and SUMO3-modified PIAS1 mediates AR cytoplasmic translocation, ubiquitination by MDM2, and proteasomal degradation; the SUMO-acceptor Lys-117 on PIAS1 is essential for AR translocation; PIAS1/SUMO3 promotes interaction between sumoylated PIAS1 and AR Lys-386/Lys-845 to form a binary complex that recruits MDM2 for AR ubiquitination.\",\n      \"method\": \"Coimmunoprecipitation, sumoylation assay, PIAS1 mutagenesis, immunostaining for AR localization, ubiquitination assay, MDM2 interaction\",\n      \"journal\": \"Cell communication and signaling\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — Co-IP plus sumoylation/ubiquitination assays plus localization imaging plus mutagenesis, single lab\",\n      \"pmids\": [\"31752909\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"PIAS1 sumoylates vimentin (VIM) at Lys-439 and Lys-445; VIM sumoylation is necessary for dynamic vimentin disassembly, and cells expressing non-SUMOylatable VIM show reduced cell migration; quantitative SUMO proteomics identified 62 putative PIAS1 substrates across diverse cellular pathways.\",\n      \"method\": \"Quantitative SUMO proteomics (SILAC-based), in vivo sumoylation assay, mutagenesis of VIM sumoylation sites, cell migration assays\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — quantitative proteomics plus in vivo sumoylation assay plus mutagenesis plus functional migration readout, single lab multiple methods\",\n      \"pmids\": [\"32047143\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"PIAS1 promotes SUMOylation of the m6A reader YTHDF2 at Lys-281, Lys-571, and Lys-572; YTHDF2 lacking sumoylation shows reduced binding to EBV transcripts and reduced EBV mRNA decay; PIAS1 synergizes with wild-type but not sumoylation-deficient YTHDF2 to limit EBV lytic replication; PIAS1 also sumoylates YTHDF1 and YTHDF3.\",\n      \"method\": \"Coimmunoprecipitation, in vivo sumoylation assay, mutagenesis, RNA binding assays, viral replication assays\",\n      \"journal\": \"mBio\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — Co-IP plus sumoylation assay plus RNA binding plus functional viral assay, single lab\",\n      \"pmids\": [\"38236021\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"SLX4IP recruits PIAS1 to the SLX4 complex and activates its E3 SUMO ligase activity; PIAS1 sumoylates the telomere protein RAP1, disrupting its interaction with TRF2 and facilitating RAP1 nucleocytoplasmic shuttling; cytosolic RAP1 then binds IKK, activating NF-κB and inducing Jagged-1/Notch signaling to institute the ALT telomere maintenance pathway.\",\n      \"method\": \"Coimmunoprecipitation, SUMOylation assay, RAP1 localization tracking, NF-κB reporter assays, ALT assays\",\n      \"journal\": \"Science signaling\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — Co-IP plus sumoylation assay plus localization plus functional pathway assays, single lab\",\n      \"pmids\": [\"34187905\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"PIAS1 interacts with influenza A virus polymerase subunit PB2 and catalyzes robust PB2 sumoylation, reducing PB2 stability; PIAS1 SUMO E3 ligase activity is required to inhibit viral RNP complex activity; PIAS1 knockdown/knockout increases IAV growth and virulence in mice, while overexpression suppresses replication.\",\n      \"method\": \"Coimmunoprecipitation, siRNA knockdown, CRISPR/Cas9 knockout, overexpression, RNP activity assay, SUMO ligase-dead mutant (C351S, W372A), protein stability assay, in vivo mouse model\",\n      \"journal\": \"PLoS pathogens\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — multiple orthogonal methods including ligase-dead mutant, in vivo mouse model, CRISPR KO, RNP activity assay, single lab\",\n      \"pmids\": [\"35377920\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Necdin binds PIAS1 central conserved domains and suppresses PIAS1-dependent sumoylation of substrates STAT1 and PML; necdin promotes ubiquitin-proteasome-mediated degradation of PIAS1 specifically within the nuclear matrix.\",\n      \"method\": \"Coimmunoprecipitation, sumoylation assays, ubiquitination/proteasome assays, nuclear matrix fractionation, PIAS1 terminal deletion mutants\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — Co-IP plus sumoylation suppression assay plus degradation assay plus fractionation, single lab\",\n      \"pmids\": [\"24911587\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"PIAS1 interacts with STI1 (stress-inducible phosphoprotein 1) through aa 450–480 of PIAS1 (mapped by surface plasmon resonance and yeast two-hybrid); PIAS1 overexpression promotes STI1 nuclear retention and co-directs STI1 and Hsp90 to specific sub-nuclear regions; PIAS1 can act as a SUMO E3 ligase for STI1 (5 sites identified by MS), but PIAS1-mediated nuclear retention of STI1 can occur through direct interaction even with non-sumoylatable STI1; PIAS1 knockdown impairs radiation-induced nuclear STI1 accumulation.\",\n      \"method\": \"Yeast two-hybrid, surface plasmon resonance, coimmunoprecipitation, mass spectrometry of SUMOylation sites, RNAi, subcellular fractionation/localization assays\",\n      \"journal\": \"Molecular & cellular proteomics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — SPR plus Co-IP plus MS plus RNAi plus localization, multiple methods single lab\",\n      \"pmids\": [\"23938469\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"PIAS1 and TIF1γ form a trimeric complex with SnoN to collaboratively promote SnoN SUMOylation and suppress EMT; PIAS1 and TIF1γ act in an interdependent (not additive) manner for EMT suppression in breast organoids.\",\n      \"method\": \"Coimmunoprecipitation of trimeric complex, SUMOylation assay, loss-of-function (siRNA), 3D breast organoid EMT assay\",\n      \"journal\": \"Cell death and differentiation\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — Co-IP plus sumoylation assay plus functional organoid readout, single lab\",\n      \"pmids\": [\"32770107\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"PIAS1 is a SUMO E3 ligase that physically docks with activated STAT1 dimers (via its C-terminal domain recognizing the Stat1 N-terminal domain) and blocks their DNA binding, thereby selectively repressing IFN/cytokine-inducible gene transcription; it additionally sumoylates a broad spectrum of substrates—including p53, Sp3, androgen receptor, FAK, p73, PML, HTT, PCNA, vimentin, MYC, RUNX proteins, and viral factors—to regulate their activity, stability, or localization, and it is itself regulated by IKKα-mediated phosphorylation at Ser90 (required for NF-κB repression), PRMT1-mediated arginine methylation at Arg303 (required for late-phase STAT1 repression), and SUMO3-modification at Lys117 (required for AR degradation), while structurally its N-terminal SAP domain forms a four-helix bundle that binds A/T-rich DNA and mediates interactions with substrates and chromatin.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"PIAS1 is a nuclear SUMO E3 ligase that controls gene expression and genome integrity by both catalytic SUMO conjugation of diverse substrates and non-enzymatic protein interactions, and it acts as a central negative regulator of inflammatory and innate-immune transcription [#0, #9, #2]. Its founding activity is selective repression of cytokine-inducible transcription: PIAS1 docks onto activated, tyrosine-phosphorylated STAT1 dimers through its C-terminal domain binding the STAT1 N-terminal region and blocks STAT1 DNA binding, while in vivo a subset of IFN-inducible genes is derepressed in Pias1-null cells with increased STAT1 promoter recruitment [#0, #1, #9]. In parallel it represses NF-\\u03baB by binding nuclear p65 and blocking its DNA binding [#11]. As a RING-type SUMO E3 ligase, PIAS1 binds Ubc9 and SUMO and conjugates SUMO to a broad substrate spectrum\\u2014p53, Sp3, androgen receptor, FAK, p73, RUNX proteins, MYC, PML, vimentin, and PCNA\\u2014to control substrate activity, localization, or proteasomal turnover, often by priming substrates for STUbL (RNF4)-dependent degradation [#2, #3, #4, #36, #37, #38, #43, #46]. PIAS1 functions in DNA repair, being recruited via its SAP domain to double-strand breaks where it drives SUMO accumulation and the productive assembly of 53BP1, BRCA1, and RNF168, and it promotes PCNA Lys-164 sumoylation required for error-free template-switch damage tolerance [#20, #43]. Structurally, its N-terminal SAP domain forms a four-helix bundle that binds A/T-rich DNA and substrates, and PIAS1 forms a non-covalent ternary complex with SUMO1 and UBC9 required for transcriptional repression [#8, #31]. Its activity is tuned by post-translational modification\\u2014IKK\\u03b1-mediated Ser90 phosphorylation enabling NF-\\u03baB repression and PRMT1-mediated Arg303 methylation enabling late-phase STAT1 repression [#15, #18]. PIAS1 additionally restricts viral replication (HSV-1, EBV, influenza A) and modulates Huntingtin sumoylation and aggregation in models of Huntington's disease [#41, #49, #29, #40].\",\n  \"teleology\": [\n    {\n      \"year\": 1998,\n      \"claim\": \"Established PIAS1's founding function by showing it selectively represses STAT1-dependent transcription, defining a paradigm of inhibitor of activated STAT.\",\n      \"evidence\": \"Co-IP, DNA binding and reporter assays in cytokine-stimulated cells\",\n      \"pmids\": [\"9724754\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not resolve the structural basis of the STAT1 interaction\", \"Mechanism of selectivity for STAT1 over STAT2/3 unexplained\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Mapped the interaction to PIAS1 C-terminus binding STAT1 N-terminus and showed PIAS1 selectively recognizes STAT1 dimers, explaining how repression is coupled to activation.\",\n      \"evidence\": \"Yeast two-hybrid, in vitro binding, domain deletion, dimer/monomer discrimination\",\n      \"pmids\": [\"10805787\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No structure of the PIAS1\\u2013STAT1 complex\", \"How dimer recognition prevents DNA binding not shown at atomic level\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Defined PIAS1 as a bona fide SUMO E3 ligase by reconstituting Ubc9-dependent p53 sumoylation and showing RING-domain dependence, transforming it from a STAT inhibitor into an enzyme.\",\n      \"evidence\": \"In vitro and cell-based SUMOylation assays with RING-domain mutagenesis\",\n      \"pmids\": [\"11583632\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional consequence of p53 sumoylation not fully resolved here\", \"Substrate range unknown at the time\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Extended the ligase function to transcription factors (Sp3, AR), establishing that PIAS1-mediated sumoylation silences transcriptional activity without altering DNA binding, and identified a RING-independent p53 coactivator role.\",\n      \"evidence\": \"In vitro/in vivo sumoylation, mutagenesis, reporter assays, Co-IP\",\n      \"pmids\": [\"12356736\", \"12177000\", \"11788578\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether sumoylation versus binding drives each transcriptional outcome not cleanly separated\", \"Endogenous substrate-specificity determinants unmapped\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Showed sumoylation can activate rather than silence a substrate, with FAK sumoylation at Lys-152 driving nuclear localization and autophosphorylation, broadening the functional outcomes of PIAS1 catalysis.\",\n      \"evidence\": \"Co-IP, in vitro binding, cell-based sumoylation, kinase assays, fractionation\",\n      \"pmids\": [\"14500712\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Physiological context of nuclear FAK function unclear\", \"Downstream nuclear FAK targets not defined\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Demonstrated PIAS1 is physiologically required to restrain innate immunity in vivo and resolved the SAP-domain four-helix-bundle structure that binds A/T-rich DNA, linking chromatin association to function.\",\n      \"evidence\": \"Pias1-/- mice, ChIP, gene expression; NMR structure with DNA/p53 binding assays\",\n      \"pmids\": [\"15311277\", \"15133049\", \"15572666\", \"15572677\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How the SAP domain selects specific promoters in vivo not fully established\", \"Genome-wide direct targets not defined at this stage\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Generalized the transcriptional-repressor role beyond STAT1 to NF-\\u03baB p65 and revealed context-dependent coactivator functions (SRF-driven smooth muscle genes), establishing PIAS1 as a bidirectional transcriptional regulator.\",\n      \"evidence\": \"Pias1-/- mice, Co-IP, DNA binding, ChIP; mammalian two-hybrid and SRF-/- cells\",\n      \"pmids\": [\"15657437\", \"16135793\", \"16144832\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"What dictates repressor versus coactivator behavior unclear\", \"Promoter-context determinants of selectivity unresolved\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Identified phosphorylation as the activating signal, with IKK\\u03b1 phosphorylating Ser90 to license NF-\\u03baB repression and promoter recruitment, integrating PIAS1 into proinflammatory signaling kinetics.\",\n      \"evidence\": \"Phospho-mutant analysis, Co-IP, ChIP in TNF/LPS-stimulated cells\",\n      \"pmids\": [\"17540171\", \"17440973\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural effect of Ser90 phosphorylation unknown\", \"Whether phosphorylation alters catalytic versus binding activity not separated\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Showed arginine methylation at Arg303 by PRMT1 is required for late-phase STAT1 repression and defined PIAS1 recruitment to DSBs via its SAP domain, coupling it to SUMO-driven DNA repair factor assembly.\",\n      \"evidence\": \"In vitro methylation, MS, mutagenesis, ChIP; laser micro-irradiation, SAP mutants, epistasis\",\n      \"pmids\": [\"19136629\", \"20016603\", \"19620279\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How methylation and phosphorylation are coordinated unknown\", \"Direct DSB-site SUMO substrates of PIAS1 not all defined\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Linked PIAS1 to epigenetic gene silencing and lineage control by showing it maintains repressive chromatin at the Foxp3 promoter and modulates developmental signaling (Hedgehog/Gli, TGF\\u03b2/SnoN), expanding its role to chromatin and differentiation.\",\n      \"evidence\": \"Pias1-/- mice, ChIP, bisulfite sequencing; in vivo neural tube and EMT assays\",\n      \"pmids\": [\"20966256\", \"20711444\", \"21103059\", \"20421208\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct versus indirect chromatin recruitment not fully separated\", \"How DNMT/HP1 recruitment is targeted unresolved\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Defined the SUMO\\u2013UBC9\\u2013PIAS1 ternary complex required for repression and connected PIAS1 to neurodegeneration by identifying it as the HTT SUMO ligase regulating insoluble HTT accumulation.\",\n      \"evidence\": \"NMR/ITC/BRET biophysics; E3 ligase screen, gain/loss-of-function, Drosophila HD model\",\n      \"pmids\": [\"24174529\", \"23871671\", \"24061474\", \"23938469\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo relevance of the ternary complex to specific substrates untested\", \"Mechanism converting HTT sumoylation to insolubility unclear\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Mapped PIAS1 genome-wide as a chromatin-bound AR coregulator and established it as the MYC/c-Myc SUMO ligase controlling MYC stability and oncogenic activity, embedding it in cancer-relevant transcription programs.\",\n      \"evidence\": \"ChIP-seq, RNAi, transcriptomics; Co-IP, sumoylation, MYC turnover/phospho analysis, MS\",\n      \"pmids\": [\"25552417\", \"27239040\", \"25895136\", \"24777122\", \"25031400\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Causal contribution of individual substrate sumoylations to tumorigenesis not isolated\", \"Cooperation with FOXA1/pioneer factors mechanistically incomplete\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Demonstrated in vivo therapeutic relevance in Huntington's disease, where striatal PIAS1 knockdown reduces mHTT accumulation and improves behavior, and showed PIAS1 restricts HSV-1 at PML nuclear bodies.\",\n      \"evidence\": \"In vivo miRNA knockdown in R6/2 mice; IF localization, SIM mutants, viral replication assays\",\n      \"pmids\": [\"27146268\", \"27099310\", \"29262325\", \"24911587\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Substrate(s) mediating the HD benefit not pinned to a single target\", \"How PML-body localization is regulated dynamically unclear\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Established PIAS1 (with PIAS4) as the physiological SUMO ligase for PCNA Lys-164 required for error-free template-switch damage tolerance, giving it a defined genome-maintenance substrate by clean genetic epistasis.\",\n      \"evidence\": \"PIAS1/PIAS4 knockout cells, Ig conversion assay, PCNA sumoylation, epistasis, chimera rescue\",\n      \"pmids\": [\"30487218\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Relative substrate division of labor between PIAS1 and PIAS4 not resolved\", \"Regulation of recruitment to replication-associated lesions unclear\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Used quantitative SUMO proteomics to define a broad PIAS1 substrate landscape including vimentin, whose sumoylation regulates intermediate-filament dynamics and migration, framing PIAS1 as a global cytoskeletal and signaling SUMO regulator.\",\n      \"evidence\": \"SILAC SUMO proteomics, in vivo sumoylation, VIM site mutagenesis, migration assays; SnoN/TIF1\\u03b3 organoid study\",\n      \"pmids\": [\"32047143\", \"32770107\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Most of the 62 putative substrates lack functional validation\", \"How substrate selectivity is achieved genome-wide unknown\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Consolidated PIAS1 as a broad antiviral restriction factor by showing it sumoylates and destabilizes influenza A PB2 and the m6A reader YTHDF2 to limit IAV and EBV replication, with ligase activity required.\",\n      \"evidence\": \"Co-IP, CRISPR KO, ligase-dead mutants, RNP/stability assays, in vivo mouse IAV model\",\n      \"pmids\": [\"35377920\", \"38236021\", \"34187905\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Breadth of antiviral substrate targeting across virus families incomplete\", \"How host SUMO machinery is mobilized during infection unresolved\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"It remains unresolved how PIAS1 achieves substrate and promoter selectivity in vivo\\u2014how its post-translational modifications, SAP-domain DNA binding, and SIM-mediated localization are integrated to choose targets among its hundreds of potential substrates.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unifying model linking PIAS1 modification state to substrate choice\", \"Structural basis of substrate discrimination beyond STAT1 unknown\", \"Functional validation lacking for most proteomically identified substrates\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [2, 3, 4, 6, 43, 46, 49]},\n      {\"term_id\": \"GO:0016874\", \"supporting_discovery_ids\": [2, 3, 43]},\n      {\"term_id\": \"GO:0003677\", \"supporting_discovery_ids\": [8, 24]},\n      {\"term_id\": \"GO:0140110\", \"supporting_discovery_ids\": [0, 3, 13, 21]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0, 1, 11, 9]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [0, 9, 11, 35]},\n      {\"term_id\": \"GO:0000228\", \"supporting_discovery_ids\": [20, 43]},\n      {\"term_id\": \"GO:0016604\", \"supporting_discovery_ids\": [41]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [0, 9, 11]},\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [2, 3, 36, 37, 46]},\n      {\"term_id\": \"R-HSA-73894\", \"supporting_discovery_ids\": [20, 43]},\n      {\"term_id\": \"R-HSA-74160\", \"supporting_discovery_ids\": [0, 13, 21, 35]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [29, 40, 41, 49]}\n    ],\n    \"complexes\": [\n      \"PIAS1-SUMO1-UBC9 ternary complex\",\n      \"SLX4 complex (via SLX4IP)\",\n      \"CP2c/CP2b hexameric DNA-binding complex\",\n      \"PNKP transcription-coupled repair complex\"\n    ],\n    \"partners\": [\n      \"STAT1\",\n      \"UBC9\",\n      \"RELA\",\n      \"TP53\",\n      \"IKBKA\",\n      \"PRMT1\",\n      \"FOXA1\",\n      \"PML\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":8,"faith_total":8,"faith_pct":100.0}}