{"gene":"TIPARP","run_date":"2026-04-28T21:42:59","timeline":{"discoveries":[{"year":2012,"finding":"TIPARP (TiPARP/ARTD14/PARP7) is a mono-ADP-ribosyltransferase that auto-ribosylates and ribosylates core histones; it directly interacts with AHR in the nucleus, co-localizes at CYP1A1, and functions as a transcriptional repressor of AHR by promoting AHR proteolytic degradation, establishing a negative feedback loop in AHR signaling. Inhibition required both the zinc-finger and catalytic domains.","method":"In vitro ADP-ribosylation assay, RNAi knockdown, overexpression reporter assay, deletion/mutagenesis studies, co-immunoprecipitation, co-localization by immunofluorescence, ChIP","journal":"Nucleic Acids Research","confidence":"High","confidence_rationale":"Tier 1–2 — multiple orthogonal methods (in vitro enzymatic assay, mutagenesis, Co-IP, reporter, KO MEFs) in a single rigorous study","pmids":["23275542"],"is_preprint":false},{"year":2010,"finding":"TIPARP mediates TCDD-induced suppression of hepatic gluconeogenesis by consuming NAD+, reducing SIRT1 activation of PGC1α, and increasing PGC1α acetylation and proteasomal degradation, thereby suppressing PEPCK and G6Pase transcription. TIPARP overexpression reproduced TCDD effects while TIPARP silencing diminished them.","method":"TIPARP overexpression and siRNA knockdown in hepatic cells, glucose output assay, NAD+ measurement, qPCR, western blot","journal":"Journal of Biological Chemistry","confidence":"High","confidence_rationale":"Tier 2 — gain- and loss-of-function with multiple biochemical readouts in same study","pmids":["20876576"],"is_preprint":false},{"year":2013,"finding":"TCDD-induced TIPARP directly ADP-ribosylates PEPCK (both cytosolic and mitochondrial forms), identifying ADP-ribosylation as a novel post-translational modification of PEPCK downstream of AHR activation.","method":"In vitro ADP-ribosylation assay, immunoprecipitation of ADP-ribosylated proteins from TCDD-treated cells","journal":"Journal of Biological Chemistry","confidence":"Medium","confidence_rationale":"Tier 2 — direct biochemical assay but single laboratory","pmids":["23770670"],"is_preprint":false},{"year":2015,"finding":"TIPARP mono-ADP-ribosylates AHR (but not ARNT/AHR nuclear translocator); this ADP-ribosylation promotes AHR degradation. The de-ADP-ribosylase MACROD1 (but not MACROD2) reverses TIPARP's repressive effect on AHR. Loss of Tiparp in mice dramatically increases sensitivity to dioxin-induced steatohepatitis and lethality.","method":"In vitro ADP-ribosylation assay with AHR and ARNT substrates, MACROD1/2 rescue experiments, Tiparp−/− mouse model with TCDD challenge","journal":"Journal of Biological Chemistry","confidence":"High","confidence_rationale":"Tier 1–2 — in vitro substrate identification, macrodomain rescue, and in vivo KO model with defined phenotype","pmids":["25975270"],"is_preprint":false},{"year":2016,"finding":"TIPARP mono-ADP-ribosylates LXRα and LXRβ and acts as a co-activator of LXR transcriptional activity; the zinc-finger and catalytic domains are required. TIPARP interacts with LXRs via an N-terminal sequence (aa 209–236). MACROD1 (not MACROD2) interacts with LXRs in a TIPARP-dependent manner and prevents the TIPARP-dependent increase in LXR activity.","method":"In vitro ADP-ribosylation assay, reporter gene assay, co-immunoprecipitation, peptide array, immunofluorescence co-localization, Tiparp−/− MEFs and mice","journal":"Biochemical Journal","confidence":"High","confidence_rationale":"Tier 1–2 — multiple orthogonal methods (in vitro ribosylation, Co-IP, mutagenesis, KO cells/mice) in a single study","pmids":["26814197"],"is_preprint":false},{"year":2014,"finding":"Parp7 occupies key pluripotency gene loci (Nanog, Pou5f1, Sox2, Stella, Tet1, Zfp42) in embryonic stem cells; loss of Parp7 (or inhibition of ADP-ribosylating activity) decreases ground-state pluripotency and increases propensity to differentiate, placing Parp7 at the genetic-epigenetic interface of pluripotency networks.","method":"ChIP-seq, Parp1/Parp7 KO ES cells, inhibitor treatment, pluripotency marker analysis","journal":"Nucleic Acids Research","confidence":"High","confidence_rationale":"Tier 2 — ChIP-seq occupancy plus KO phenotype with multiple pluripotency readouts","pmids":["25034692"],"is_preprint":false},{"year":2018,"finding":"Nuclear localization of TIPARP depends on a short N-terminal sequence and its zinc-finger domain. The minimum catalytically active region spans aa 400–657. TIPARP activity is sensitive to iodoacetamide and hydroxylamine (implicating cysteines and acidic residues as acceptors). Mass spectrometry and ETD identified cysteine 39 as an auto-ADP-ribosylation site. TIPARP mono-ADP-ribosylates AHR at multiple peptides. Both catalytic activity and zinc-finger domain are required for AHR repression in cells.","method":"Deletion mutagenesis, in vitro ADP-ribosylation assay, chemical sensitivity assays (MIBG, iodoacetamide, hydroxylamine), mass spectrometry with ETD fragmentation, subcellular fractionation/immunofluorescence","journal":"Biochemical Journal","confidence":"High","confidence_rationale":"Tier 1 — in vitro biochemistry with mutagenesis and MS-based site mapping","pmids":["30373764"],"is_preprint":false},{"year":2018,"finding":"Hepatocyte-specific deletion of TIPARP (Tiparpfl/fl CreAlb mice) is sufficient to increase sensitivity to dioxin-induced steatohepatitis and lethality, demonstrating that TIPARP acts as a negative regulator of AHR in hepatocytes. Tiparp-null mice show augmented AHR target gene expression and altered lipid/amino acid metabolism.","method":"Conditional Cre-lox knockout mouse model, TCDD challenge, histology, serum ALT, RNA-seq, metabolomics","journal":"Toxicological Sciences","confidence":"High","confidence_rationale":"Tier 2 — tissue-specific KO with mechanistic AHR readouts and metabolomics","pmids":["29873790"],"is_preprint":false},{"year":2020,"finding":"TiPARP forms ADP-ribosylation-dependent nuclear condensates/nuclear bodies that recruit HIF-1α and the E3 ubiquitin ligase HUWE1, promoting ubiquitination and proteasomal degradation of HIF-1α. Similarly, TiPARP promotes degradation of c-Myc and estrogen receptor, establishing TiPARP as a negative-feedback regulator of multiple oncogenic transcription factors.","method":"Live-cell imaging of nuclear condensates, co-immunoprecipitation, ubiquitination assay, proteasome inhibitor experiments, xenograft mouse models","journal":"PNAS","confidence":"High","confidence_rationale":"Tier 2 — Co-IP, ubiquitination assay, condensate imaging, and in vivo xenograft with multiple substrates","pmids":["32482854"],"is_preprint":false},{"year":2021,"finding":"PARP7 is a negative regulator of nucleic acid sensing in tumor cells; its inhibition restores type I interferon (IFN) signaling responses to nucleic acids, directly inhibits cancer cell proliferation, and activates antitumor immunity. The mechanism is dependent on inducing type I IFN signaling in tumor cells, and antitumor effects require STING pathway and TBK1 activity.","method":"PARP7 inhibitor (RBN-2397) in cancer cell lines and mouse models (xenograft and syngeneic), IFN pathway reporter assays, immune cell depletion experiments","journal":"Cancer Cell","confidence":"High","confidence_rationale":"Tier 2 — pharmacologic inhibition plus in vivo models with immune-dependency epistasis","pmids":["34375612"],"is_preprint":false},{"year":2021,"finding":"PARP-13 (ZAP), a critical antiviral innate immune regulator, is a major substrate of PARP-7-mediated MARylation; PARP-7 preferentially MARylates PARP-13 on cysteine residues within its RNA-binding zinc-finger domain. Proteome-wide analysis reveals cysteine as the predominant MARylation acceptor for PARP-7.","method":"Chemical genetics (analog-sensitive PARP-7), proximity labeling, proteome-wide ADP-ribosylation site profiling by mass spectrometry","journal":"eLife","confidence":"High","confidence_rationale":"Tier 1 — chemical genetics plus MS-based proteome-wide site mapping with orthogonal methods","pmids":["33475084"],"is_preprint":false},{"year":2021,"finding":"PARP-7 MARylates α-tubulin to promote microtubule instability in ovarian cancer cells, regulating cancer cell growth and motility. PARP-7 substrates were identified using an NAD+ analog-sensitive approach coupled with mass spectrometry.","method":"NAD+ analog-sensitive PARP-7 coupled with mass spectrometry, cell growth/migration assays with PARP-7 depletion, gene expression analysis","journal":"eLife","confidence":"High","confidence_rationale":"Tier 1–2 — analog-sensitive chemical genetics plus MS substrate identification and functional readout","pmids":["33475085"],"is_preprint":false},{"year":2021,"finding":"PARP7 mono-ADP-ribosylates estrogen receptor α (ERα); the modification is mapped by mass spectrometry to peptides in the ligand-independent transactivation domain, and the ERα hinge region is required for PARP7-dependent MARylation. PARP7 overexpression reduces ligand-dependent ERα signaling; PARP7 KO MCF-7 cells show increased ERα target gene expression and proliferation.","method":"Co-immunoprecipitation, mass spectrometry, truncated ERα variant experiments, PARP7 KO cells (CRISPR), reporter assays","journal":"Cells","confidence":"High","confidence_rationale":"Tier 2 — Co-IP with MS site mapping plus KO functional validation","pmids":["33799807"],"is_preprint":false},{"year":2021,"finding":"PARP7 protein stability is regulated post-transcriptionally by androgen signaling: PARP7 has an extremely short half-life (~4.5 min) that is extended to ~25.6 min by androgen/AR signaling in prostate cancer cells. Androgen-dependent stabilization leads to nuclear accumulation of PARP7. Mutations in the catalytic domain, zinc-finger, or WWE domains each reduce the degradation rate of PARP7.","method":"Cycloheximide chase assay, androgen treatment, domain-mutation analysis, subcellular fractionation","journal":"Cells","confidence":"High","confidence_rationale":"Tier 1–2 — direct protein stability measurement with mutagenesis and androgen manipulation","pmids":["33572475"],"is_preprint":false},{"year":2021,"finding":"PARP7 mono-ADP-ribosylates the androgen receptor (AR) in an agonist-conformation- and nuclear-localization-dependent manner. The PARP7 Cys3His1 zinc finger (ZF) is critical for AR ADP-ribosylation and for PARP7 nuclear import; ZF mutations abrogate PARP7 enhancement of AR-dependent transcription of MYBPC1 without reducing catalytic activity or AR binding.","method":"In vitro ADP-ribosylation assay, ZF mutagenesis, nuclear import assays, reporter gene assay, AR conformation mutants","journal":"Biochemical Journal","confidence":"High","confidence_rationale":"Tier 1–2 — in vitro biochemistry with domain mutagenesis and conformation-dependence experiments","pmids":["34264286"],"is_preprint":false},{"year":2021,"finding":"CUL4B (E3 ubiquitin ligase) and TiPARP cooperate to promote TCDD-activated AHR nuclear export and proteasomal degradation; knockdown of TiPARP in CUL4B-null MEFs completely abolished AHR degradation after TCDD, demonstrating that TiPARP is required for AHR nuclear export downstream of CUL4B.","method":"MEF cell lines with CUL4B deletion and TiPARP siRNA knockdown, AHR protein level/localization assay, AHR transcriptional activity measurement","journal":"Journal of Biological Chemistry","confidence":"High","confidence_rationale":"Tier 2 — epistasis using double KO/KD with defined molecular phenotype (AHR export/degradation)","pmids":["34146543"],"is_preprint":false},{"year":2021,"finding":"Loss of TIPARP catalytic activity (H532A knock-in mouse) increases sensitivity to TCDD-induced hepatotoxicity and lethality to the same degree as full TIPARP loss, confirming that the ADP-ribosyltransferase activity of TIPARP is the mechanistic basis for its AHR repressor function in vivo.","method":"Catalytic mutant knock-in mouse (TiparpH532A), TCDD challenge, RNA-seq, histology, ALT measurements","journal":"Toxicological Sciences","confidence":"High","confidence_rationale":"Tier 1–2 — catalytic-mutant knock-in mouse with in vivo phenotype identical to KO","pmids":["34129049"],"is_preprint":false},{"year":2023,"finding":"PARP7 MARylates the AP-1 transcription factor FRA1 on cysteine C97; this modification protects FRA1 from proteasomal degradation via PSMC3. Loss of FRA1 ADP-ribosylation (by PARP7 inhibition or C97 mutation) promotes IRF1- and IRF3-dependent cytokine and proapoptotic gene expression, culminating in CASP8-mediated apoptosis.","method":"PARP7 inhibitor (RBN-2397), site-directed mutagenesis of FRA1 C97, co-immunoprecipitation, proteasome inhibition, gene expression analysis","journal":"PNAS","confidence":"High","confidence_rationale":"Tier 1–2 — site-specific mutagenesis of substrate, proteasome assay, and downstream pathway analysis","pmids":["38011562"],"is_preprint":false},{"year":2019,"finding":"Loss of Tiparp in mice causes aberrant cortical layering, particularly increased cell density in upper cortical layers with predominant effects on GABAergic neuron distribution, reduced neural progenitor cell proliferation, and slower neural stem cell migration. α-tubulin mono-ADP-ribosylation levels are reduced in Tiparp−/− cells, suggesting TIPARP MARylates α-tubulin during cortical development.","method":"Tiparp−/− mouse histological analysis, cell counting, neural stem cell migration assay, MAR-tubulin detection","journal":"eNeuro","confidence":"Medium","confidence_rationale":"Tier 2 — KO mouse with defined cellular phenotype plus biochemical MAR-tubulin measurement, single study","pmids":["31704703"],"is_preprint":false},{"year":2022,"finding":"AHR loss was identified as a mechanism of resistance to PARP7 inhibitor RBN-2397 via a genome-wide CRISPR screen; multiple cohesin complex components also modulate RBN-2397 response. AHR activators and inhibitors modulate cellular response to PARP7 inhibition, establishing AHR as a key determinant of PARP7 inhibitor sensitivity.","method":"Genome-wide CRISPR screen, AHR modulator experiments","journal":"Molecular Cancer Therapeutics","confidence":"Medium","confidence_rationale":"Tier 2 — genome-wide CRISPR epistasis screen, validated with AHR modulators","pmids":["35439318"],"is_preprint":false},{"year":2022,"finding":"PARP7 catalytic activity regulates its own protein levels (autoMARylation promotes instability); treatment with PARP7 inhibitors increases PARP7 protein levels in cells, and this increase correlates with the magnitude of type I interferon gene expression.","method":"PARP7 inhibitor treatment (KMR-206 and RBN-2397), western blot for PARP7 protein levels, IFN-β reporter assays","journal":"Cell Chemical Biology","confidence":"Medium","confidence_rationale":"Tier 2 — pharmacological inhibition with protein level quantification, replicated with two structurally distinct inhibitors","pmids":["36529140"],"is_preprint":false},{"year":2025,"finding":"PARP7 inhibits type I IFN production by directly interacting with IRF3 through its catalytic domain and disrupting the IRF3:CBP/p300 transcriptional holocomplex required for IFN-I production. This is MARylation-dependent. Irf3−/− or transcription-defective Irf3S1/S1 or Sting−/− rescues Parp7H532A/H532A autoimmunity and lung disease, placing PARP7 upstream of IRF3 and STING.","method":"Parp7−/− and Parp7H532A/H532A mice, genetic epistasis with Irf3−/−/Irf3S1/S1/Sting−/− rescue, Co-IP of PARP7-IRF3 and IRF3-CBP/p300, MARylation assays","journal":"Journal of Experimental Medicine","confidence":"High","confidence_rationale":"Tier 1–2 — MARylation-dependent mechanism established by catalytic mutant knock-in plus genetic epistasis with multiple pathway components","pmids":["39969510"],"is_preprint":false},{"year":2025,"finding":"PARP7 generates an ADP-ribosyl degron on the DNA-binding domain of AR (chromatin-bound AR), which is recognized by the ADP-ribose reader domain of the E3 ubiquitin ligase DTX2, leading to non-conventional ubiquitin conjugation to ADP-ribosyl-cysteine and proteasomal degradation of AR. Mathematical modeling and an AR DNA-binding mutant confirmed that PARP7 preferentially ADP-ribosylates chromatin-bound AR.","method":"Mathematical modeling, AR DNA-binding mutant rescue, DTX2 reader domain binding assay, in vitro ubiquitination assay, mass spectrometry","journal":"EMBO Journal","confidence":"High","confidence_rationale":"Tier 1 — reconstituted degradation pathway with substrate mutant validation and mathematical modeling","pmids":["40681873"],"is_preprint":false},{"year":2025,"finding":"PARP7 functions as a nuclear NAD+ sensor: at higher nuclear NAD+ concentrations (in undifferentiated preadipocytes), PARP7 is catalytically active for autoMARylation; as NAD+ declines upon differentiation, autoMARylation decreases. AutoMARylation promotes PARP7 instability via the E3 ligases DTX2 and RNF114 through the ubiquitin-proteasome pathway. Stabilized PARP7 serves as a coregulator of C/EBPβ by stimulating p300-mediated H3K27ac and C/EBPβ genome-wide binding.","method":"NAD+ measurement in preadipocytes vs adipocytes, in vitro autoMARylation assay, DTX2/RNF114 Co-IP/ubiquitination assay, ChIP-seq for C/EBPβ and H3K27ac, PARP7 KO mouse model with fat-pad analysis","journal":"Cell Reports","confidence":"High","confidence_rationale":"Tier 1–2 — in vitro biochemistry with ChIP-seq and KO mouse model confirming multiple mechanistic steps","pmids":["41621069"],"is_preprint":false},{"year":2025,"finding":"PARP7 is a proteotoxic stress sensor: during proteotoxic stress PARP7 is stabilized and MARylates substrates that accumulate in cytoplasmic foci containing ubiquitin and p62, subsequently trafficked to aggresomes and degraded by autophagy. Ubiquitination is required for this process. PARP7 inhibition impedes accumulation of MARylated proteins during stress.","method":"PARP7 inhibitor treatment during proteotoxic stress, immunofluorescence for aggresome markers, ADP-ribosylation detection, ubiquitination pathway blockade","journal":"EMBO Journal","confidence":"Medium","confidence_rationale":"Tier 2 — pharmacological inhibition with imaging and biochemical readouts, single study","pmids":["40836037"],"is_preprint":false},{"year":2025,"finding":"p300 and CBP are direct nuclear PARP7 substrates; PARP7 contains an α-helical domain essential for p300/CBP interaction, MARylation, and their proteasomal degradation. Disrupting PARP7–p300/CBP interaction prevents PARP7's suppression of IFNβ. PARP7 inhibitors induce IFNβ via two mechanisms: inhibiting MARylation of p300/CBP (loss-of-function) and stabilizing the PARP7–p300/CBP complex (gain-of-function).","method":"Analog-sensitive chemical genetic approach, Co-IP, domain deletion mutagenesis, proteasome inhibition, IFNβ reporter assay","journal":"bioRxiv (preprint)","confidence":"Medium","confidence_rationale":"Tier 1–2 — chemical genetics plus mutagenesis and functional readout, but preprint not yet peer-reviewed","pmids":["40631120"],"is_preprint":true},{"year":2025,"finding":"DTX2 is the E3 ligase responsible for degrading ADP-ribosylated PARP7, AHR, and other PARP7 substrates; mono-ADP-ribosylation by PARP7 acts as a degradation mark. Blocking the ubiquitin/proteasome pathway reveals high levels of endogenous ADP-ribosylation by PARP7 on PARP7 itself and AHR.","method":"Ubiquitin pathway blockade, mass spectrometry identification of ADP-ribosylated substrates, DTX2 KO/knockdown, Co-IP","journal":"EMBO Journal","confidence":"High","confidence_rationale":"Tier 2 — endogenous substrate identification under physiological conditions with E3 ligase genetic validation","pmids":["41326691"],"is_preprint":false},{"year":2024,"finding":"TIPARP interacts with EIF3B (eukaryotic translation initiation factor 3 subunit B) through nucleoplasmic redistribution, leading to mitochondrial dysfunction. Knockdown of Tiparp or inhibition with a TIPARP inhibitor (XG-04-B1) restores mitochondrial homeostasis in ischemic stroke mice. EIF3B is identified as a direct target of TIPARP.","method":"Co-immunoprecipitation/interaction assay, Tiparp knockdown and inhibitor treatment in ischemic stroke mouse model, mitochondrial function assays","journal":"Pharmacological Research","confidence":"Medium","confidence_rationale":"Tier 2–3 — Co-IP substrate identification plus KD/inhibitor phenotype, single study","pmids":["39547463"],"is_preprint":false},{"year":2024,"finding":"METTL16 directly binds TIPARP mRNA and enhances its m6A modification, thereby stabilizing TIPARP transcripts and upregulating TIPARP protein expression. This METTL16-m6A-TIPARP axis promotes cerebral ischemia-reperfusion injury; TIPARP overexpression abolishes protective effects of METTL16 knockdown.","method":"RIP assay, m6A-RIP-qPCR, cycloheximide chase for protein stability, MCAO mouse model, rescue experiments with TIPARP overexpression","journal":"International Journal of General Medicine","confidence":"Medium","confidence_rationale":"Tier 2 — RIP and m6A-RIP directly demonstrate METTL16 binding and m6A modification of TIPARP mRNA with in vivo rescue","pmids":["42004240"],"is_preprint":false},{"year":2017,"finding":"AHR directly regulates TIPARP expression by binding to two genomic regions containing multiple AHR response elements (AHREs) at the TIPARP promoter; AHR also co-regulates TIPARP-AS1, a cis long non-coding RNA upstream of TIPARP exon 1, via a proximal AHRE cluster.","method":"Reporter gene and deletion assays, ChIP for AHR at TIPARP promoter, qPCR for TIPARP and TIPARP-AS1","journal":"Biochemical and Biophysical Research Communications","confidence":"Medium","confidence_rationale":"Tier 2 — ChIP plus reporter/deletion experiments, single laboratory","pmids":["29274782"],"is_preprint":false}],"current_model":"TIPARP/PARP7 is a nuclear mono-ADP-ribosyltransferase (MARylase) that uses NAD+ to transfer single ADP-ribose moieties preferentially onto cysteine residues of diverse substrate proteins—including AHR, LXRα/β, ERα, AR (on chromatin), FRA1, PARP-13, α-tubulin, p300/CBP, and PEPCK—creating an ADP-ribosyl degron recognized by ubiquitin E3 ligases (DTX2, RNF114, HUWE1) that targets substrates for proteasomal degradation; its auto-MARylation activity is tuned by nuclear NAD+ concentration (sensor function), promotes its own rapid proteasomal turnover, and the enzyme's catalytic and zinc-finger domains together mediate nuclear localization, substrate ADP-ribosylation, and transcriptional repression of AHR and type I interferon signaling, establishing TIPARP as a negative-feedback regulator of AHR, estrogen, androgen, and innate immune signaling pathways."},"narrative":{"teleology":[{"year":2010,"claim":"Before TIPARP's enzymatic activity toward specific substrates was defined, this study revealed that TCDD-induced TIPARP consumes NAD⁺ to suppress hepatic gluconeogenesis by reducing SIRT1 activity and destabilizing PGC1α, establishing TIPARP as a metabolically active ADP-ribosyltransferase with physiological consequences.","evidence":"TIPARP overexpression and siRNA knockdown in hepatic cells with NAD⁺ measurement and glucose output assays","pmids":["20876576"],"confidence":"High","gaps":["Direct ADP-ribosylation of PGC1α not shown","In vivo hepatic glucose phenotype not tested"]},{"year":2012,"claim":"The central question of what TIPARP does enzymatically was answered: TIPARP is a mono-ADP-ribosyltransferase that auto-ribosylates and ribosylates histones, interacts directly with AHR, and represses AHR transcriptional activity through a negative feedback loop requiring both the zinc-finger and catalytic domains.","evidence":"In vitro ADP-ribosylation assay, Co-IP, ChIP at CYP1A1, reporter assay with domain mutants, KO MEFs","pmids":["23275542"],"confidence":"High","gaps":["AHR residues modified by TIPARP not mapped","Mechanism of AHR degradation (proteasomal vs other) not resolved"]},{"year":2013,"claim":"PEPCK was identified as a direct ADP-ribosylation substrate of TIPARP, extending the enzyme's substrate repertoire beyond AHR to metabolic enzymes.","evidence":"In vitro ADP-ribosylation assay and immunoprecipitation from TCDD-treated cells","pmids":["23770670"],"confidence":"Medium","gaps":["Functional consequence of PEPCK MARylation on enzyme activity not determined","Single laboratory finding"]},{"year":2014,"claim":"TIPARP was placed at the genetic-epigenetic interface of pluripotency: Parp7 occupies key pluripotency loci and its loss decreases ground-state pluripotency, revealing a role beyond xenobiotic defense.","evidence":"ChIP-seq in embryonic stem cells, Parp7 KO ES cells, pluripotency marker analysis","pmids":["25034692"],"confidence":"High","gaps":["Direct substrates at pluripotency loci not identified","Whether catalytic activity or scaffolding drives the pluripotency effect is unclear"]},{"year":2015,"claim":"The AHR feedback mechanism was sharpened: TIPARP directly MARylates AHR (not ARNT), this modification promotes AHR degradation, the de-MARylase MACROD1 reverses the modification, and Tiparp-null mice exhibit extreme dioxin sensitivity, validating the pathway in vivo.","evidence":"In vitro ADP-ribosylation with AHR/ARNT, MACROD1/2 rescue, Tiparp⁻/⁻ mouse TCDD challenge","pmids":["25975270"],"confidence":"High","gaps":["AHR modification sites not mapped","Whether MACROD1 acts on AHR in vivo not tested"]},{"year":2016,"claim":"TIPARP's substrate repertoire was extended to nuclear receptors LXRα/β, where it acts as a co-activator rather than repressor, demonstrating context-dependent transcriptional outcomes of MARylation.","evidence":"In vitro ADP-ribosylation, reporter assay, Co-IP, Tiparp⁻/⁻ MEFs and mice","pmids":["26814197"],"confidence":"High","gaps":["LXR MARylation sites not mapped","Whether LXR MARylation leads to degradation or activation in vivo unclear"]},{"year":2018,"claim":"The catalytic architecture and amino acid specificity were defined: cysteine 39 was identified as an auto-MARylation site by mass spectrometry, cysteine and acidic residues serve as acceptors, the minimal catalytic region spans aa 400–657, and nuclear localization requires the N-terminal sequence and zinc-finger domain.","evidence":"Deletion mutagenesis, chemical sensitivity assays, ETD mass spectrometry, subcellular fractionation","pmids":["30373764"],"confidence":"High","gaps":["Full catalog of cysteine auto-modification sites incomplete","Structural basis for cysteine preference unknown"]},{"year":2018,"claim":"Hepatocyte-specific deletion confirmed the cell-autonomous role of TIPARP as an AHR repressor in liver, ruling out systemic or immune-mediated contributions to the dioxin-sensitivity phenotype.","evidence":"Conditional Tiparpᶠˡ/ᶠˡ CreAlb knockout mice, TCDD challenge, RNA-seq, metabolomics","pmids":["29873790"],"confidence":"High","gaps":["Contribution of non-hepatocyte TIPARP to systemic dioxin effects not addressed"]},{"year":2019,"claim":"TIPARP was shown to MARylate α-tubulin in the developing brain; Tiparp-null mice display aberrant cortical layering and impaired neural progenitor migration, connecting TIPARP's cytoskeletal substrate to a neurodevelopmental phenotype.","evidence":"Tiparp⁻/⁻ mouse brain histology, neural stem cell migration assay, MAR-tubulin detection","pmids":["31704703"],"confidence":"Medium","gaps":["Tubulin modification sites not mapped in vivo","Single study without independent replication","Causal link between tubulin MARylation and migration phenotype not formally tested"]},{"year":2020,"claim":"TIPARP was found to form ADP-ribosylation-dependent nuclear condensates that recruit HUWE1 E3 ligase and promote proteasomal degradation of HIF-1α, c-Myc, and estrogen receptor, establishing a general condensate-based degradation mechanism for oncogenic transcription factors.","evidence":"Live-cell imaging, Co-IP, ubiquitination assay, proteasome inhibitor, xenograft models","pmids":["32482854"],"confidence":"High","gaps":["Liquid-liquid phase separation properties not biophysically characterized","Whether condensate formation is required for all substrates unclear"]},{"year":2021,"claim":"Multiple parallel discoveries in 2021 dramatically expanded the substrate landscape and functional contexts: PARP-13/ZAP and α-tubulin were identified as major substrates by proteome-wide chemical genetics, confirming cysteine as the predominant acceptor; ERα and AR were shown to be MARylated with functional consequences for hormone-dependent transcription; PARP7 protein half-life was measured at ~4.5 min and is extended by androgen signaling; CUL4B was shown to cooperate with TIPARP for AHR export/degradation; a catalytic-dead knock-in mouse phenocopied the full knockout; and pharmacological PARP7 inhibition restored type I IFN signaling via the STING/TBK1 pathway to suppress tumor growth.","evidence":"Chemical genetics with analog-sensitive PARP7, proteome-wide MS, CRISPR KO cells, cycloheximide chase, catalytic-mutant knock-in mice, PARP7 inhibitor in syngeneic tumor models with immune depletion","pmids":["33475084","33475085","33799807","33572475","34264286","34146543","34129049","34375612"],"confidence":"High","gaps":["Complete cellular MARylome of PARP7 under physiological conditions not catalogued","Structural basis for substrate selectivity unresolved","Relative contributions of different E3 ligases to different substrates unclear"]},{"year":2022,"claim":"Auto-MARylation was established as a self-destabilizing mechanism: PARP7 inhibitors increase PARP7 protein levels, and this stabilization correlates with IFN induction. AHR loss was identified as a resistance mechanism to PARP7 inhibitors via genome-wide CRISPR screening.","evidence":"Two structurally distinct PARP7 inhibitors with western blot quantification; genome-wide CRISPR screen with AHR modulator validation","pmids":["36529140","35439318"],"confidence":"Medium","gaps":["E3 ligase responsible for MARylation-dependent PARP7 turnover not identified in these studies","Whether AHR-independent mechanisms of inhibitor sensitivity exist"]},{"year":2023,"claim":"Site-specific MARylation of FRA1 at cysteine C97 was shown to protect FRA1 from PSMC3-mediated proteasomal degradation; loss of this modification upon PARP7 inhibition activates IRF1/IRF3-dependent apoptosis, providing a molecular mechanism for PARP7 inhibitor antitumor activity.","evidence":"PARP7 inhibitor, FRA1 C97 mutagenesis, Co-IP with PSMC3, gene expression and apoptosis assays","pmids":["38011562"],"confidence":"High","gaps":["Whether FRA1 stabilization is the dominant antitumor mechanism or one of several parallel pathways","PSMC3 interaction mechanism not structurally resolved"]},{"year":2025,"claim":"The type I IFN suppression mechanism was resolved at the molecular level: PARP7 MARylates substrates in the IRF3–CBP/p300 axis to disrupt the transcriptional holocomplex required for IFN-β, and genetic epistasis with Irf3⁻/⁻, Irf3ˢ¹/ˢ¹, and Sting⁻/⁻ rescues autoimmunity in catalytic-dead mice, definitively placing PARP7 upstream of IRF3/STING.","evidence":"Parp7H532A/H532A mice crossed with Irf3⁻/⁻, Irf3ˢ¹/ˢ¹, Sting⁻/⁻; Co-IP of PARP7–IRF3 and IRF3–CBP/p300","pmids":["39969510"],"confidence":"High","gaps":["Specific IRF3 cysteine residues MARylated not mapped","Whether PARP7 also acts on downstream effectors (e.g. ISG products) independently of IRF3"]},{"year":2025,"claim":"The ADP-ribosyl degron concept was biochemically reconstituted: PARP7 MARylates chromatin-bound AR on its DNA-binding domain, creating a degron recognized by DTX2's ADP-ribose reader domain, leading to non-canonical ubiquitin conjugation to ADP-ribosyl-cysteine and proteasomal degradation. DTX2 was also identified as the E3 ligase for PARP7 itself and AHR.","evidence":"Mathematical modeling, AR DNA-binding mutant rescue, DTX2 reader domain binding, in vitro ubiquitination, MS; DTX2 KO/KD with endogenous substrate validation","pmids":["40681873","41326691"],"confidence":"High","gaps":["Whether DTX2 is the universal reader for all PARP7-generated degrons or specific to AR/AHR substrates","Structural details of DTX2 recognition of ADP-ribosyl-cysteine unknown"]},{"year":2025,"claim":"PARP7 was established as a nuclear NAD⁺ sensor: fluctuations in nuclear NAD⁺ tune auto-MARylation and thereby protein stability, which in turn regulates C/EBPβ-dependent adipogenesis by promoting p300-mediated H3K27 acetylation.","evidence":"NAD⁺ measurement in preadipocytes/adipocytes, in vitro autoMARylation, DTX2/RNF114 ubiquitination assay, ChIP-seq, PARP7 KO mouse fat analysis","pmids":["41621069"],"confidence":"High","gaps":["Whether NAD⁺ sensing is specific to adipogenesis or generalizable","Quantitative relationship between NAD⁺ concentration and PARP7 activity not modeled"]},{"year":2025,"claim":"PARP7 was identified as a proteotoxic stress sensor that stabilizes under stress to MARylate substrates routed to aggresomes via ubiquitin and p62 for autophagic clearance, revealing a cytoplasmic quality-control function.","evidence":"PARP7 inhibitor during proteotoxic stress, aggresome marker immunofluorescence, ADP-ribosylation detection","pmids":["40836037"],"confidence":"Medium","gaps":["Single study; identity of MARylated stress substrates not determined","Whether aggresome routing requires DTX2 or other specific E3 ligases unknown","Mechanism of PARP7 stabilization under proteotoxic stress not defined"]},{"year":null,"claim":"A complete structural model of PARP7 explaining cysteine substrate selectivity, zinc-finger-mediated substrate recognition, and the interplay between nuclear condensate formation and degron-dependent degradation remains to be determined.","evidence":"","pmids":[],"confidence":"Low","gaps":["No crystal or cryo-EM structure of full-length PARP7 or PARP7–substrate complex","Complete in vivo cysteine MARylome not catalogued","Relative contributions of DTX2, RNF114, and HUWE1 to different substrates not systematically compared"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0016740","term_label":"transferase activity","supporting_discovery_ids":[0,2,3,4,6,10,11,12,14,17,22,23]},{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[0,3,10,11,12,14,22]},{"term_id":"GO:0140110","term_label":"transcription regulator activity","supporting_discovery_ids":[0,4,5,8,21,23]},{"term_id":"GO:0140299","term_label":"molecular sensor activity","supporting_discovery_ids":[23]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[0,6,8,13,14,23]}],"pathway":[{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[0,3,9,21]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[9,10,17,21]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,3,4,8,9,12,14,21,22]},{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[0,8,13,22,23,26]},{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[1,2,23]},{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[17]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[5,18]}],"complexes":[],"partners":["AHR","DTX2","RNF114","HUWE1","IRF3","MACROD1","CUL4B","EP300"],"other_free_text":[]},"mechanistic_narrative":"TIPARP (PARP7) is a nuclear mono-ADP-ribosyltransferase that transfers single ADP-ribose units preferentially onto cysteine residues of diverse substrate proteins—including AHR, AR, ERα, LXRα/β, FRA1, PARP-13, α-tubulin, HIF-1α, p300/CBP, and PEPCK—thereby tagging them for recognition by ADP-ribose-reading E3 ubiquitin ligases (DTX2, RNF114, HUWE1) and subsequent proteasomal degradation [PMID:23275542, PMID:25975270, PMID:40681873, PMID:41326691, PMID:32482854]. This ADP-ribosyl degron mechanism establishes TIPARP as a negative-feedback repressor of AHR, estrogen receptor, and type I interferon signaling; in the interferon pathway, TIPARP MARylates IRF3 and disrupts the IRF3–CBP/p300 transcriptional complex required for IFN-β production, and genetic loss of IRF3 or STING rescues the autoimmune phenotype of catalytic-dead Parp7 knock-in mice [PMID:39969510, PMID:34375612, PMID:38011562]. TIPARP also functions as a nuclear NAD⁺ sensor: high NAD⁺ promotes autoMARylation that drives its own rapid proteasomal turnover (~4.5 min half-life), while declining NAD⁺ stabilizes the protein, enabling it to act as a transcriptional coregulator—for example, stimulating p300-mediated H3K27 acetylation and C/EBPβ chromatin binding during adipogenesis [PMID:41621069, PMID:33572475]. In vivo, Tiparp knockout or catalytic-dead knock-in mice exhibit dramatically increased sensitivity to dioxin-induced steatohepatitis, aberrant cortical neuronal layering, and spontaneous type I interferon–driven autoimmunity, underscoring the enzyme's essential homeostatic roles [PMID:25975270, PMID:34129049, PMID:31704703, PMID:39969510]."},"prefetch_data":{"uniprot":{"accession":"Q7Z3E1","full_name":"Protein mono-ADP-ribosyltransferase TIPARP","aliases":["ADP-ribosyltransferase diphtheria toxin-like 14","ARTD14","Poly [ADP-ribose] polymerase 7","PARP-7","TCDD-inducible poly [ADP-ribose] polymerase"],"length_aa":657,"mass_kda":76.2,"function":"ADP-ribosyltransferase that mediates mono-ADP-ribosylation of glutamate, aspartate and cysteine residues on target proteins (PubMed:23275542, PubMed:25043379, PubMed:30373764). Acts as a negative regulator of AHR by mediating mono-ADP-ribosylation of AHR, leading to inhibit transcription activator activity of AHR (PubMed:23275542, PubMed:30373764)","subcellular_location":"Nucleus","url":"https://www.uniprot.org/uniprotkb/Q7Z3E1/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/TIPARP","classification":"Not Classified","n_dependent_lines":331,"n_total_lines":1208,"dependency_fraction":0.2740066225165563},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/TIPARP","total_profiled":1310},"omim":[{"mim_id":"612481","title":"POLY(ADP-RIBOSE) POLYMERASE FAMILY, MEMBER 12; PARP12","url":"https://www.omim.org/entry/612481"},{"mim_id":"612480","title":"TCDD-INDUCIBLE POLY(ADP-RIBOSE) POLYMERASE; TIPARP","url":"https://www.omim.org/entry/612480"},{"mim_id":"607312","title":"ZINC FINGER CCCH DOMAIN-CONTAINING ANTIVIRAL PROTEIN 1; ZC3HAV1","url":"https://www.omim.org/entry/607312"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Microtubules","reliability":"Approved"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in 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receptor differentially regulate mammary cancer cell proliferation and STING-induced type I interferon signalling.","date":"2025","source":"Cellular oncology (Dordrecht, Netherlands)","url":"https://pubmed.ncbi.nlm.nih.gov/41432900","citation_count":0,"is_preprint":false},{"pmid":"41295982","id":"PMC_41295982","title":"Identification of a Two-Gene Biomarker Correlated with Sensitivity to Combined PARP7 Inhibition and AHR Activation in Cancer Cells.","date":"2026","source":"Cancer research communications","url":"https://pubmed.ncbi.nlm.nih.gov/41295982","citation_count":0,"is_preprint":false},{"pmid":"41979168","id":"PMC_41979168","title":"PARP7 inhibition and a STING agonist potentiate radiation-induced immunogenicity in glioblastoma.","date":"2026","source":"Oncoimmunology","url":"https://pubmed.ncbi.nlm.nih.gov/41979168","citation_count":0,"is_preprint":false},{"pmid":"41779776","id":"PMC_41779776","title":"PARP7 protects the lung epithelial barrier from diverse environmental 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[\n    {\n      \"year\": 2012,\n      \"finding\": \"TIPARP (TiPARP/ARTD14/PARP7) is a mono-ADP-ribosyltransferase that auto-ribosylates and ribosylates core histones; it directly interacts with AHR in the nucleus, co-localizes at CYP1A1, and functions as a transcriptional repressor of AHR by promoting AHR proteolytic degradation, establishing a negative feedback loop in AHR signaling. Inhibition required both the zinc-finger and catalytic domains.\",\n      \"method\": \"In vitro ADP-ribosylation assay, RNAi knockdown, overexpression reporter assay, deletion/mutagenesis studies, co-immunoprecipitation, co-localization by immunofluorescence, ChIP\",\n      \"journal\": \"Nucleic Acids Research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — multiple orthogonal methods (in vitro enzymatic assay, mutagenesis, Co-IP, reporter, KO MEFs) in a single rigorous study\",\n      \"pmids\": [\"23275542\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"TIPARP mediates TCDD-induced suppression of hepatic gluconeogenesis by consuming NAD+, reducing SIRT1 activation of PGC1α, and increasing PGC1α acetylation and proteasomal degradation, thereby suppressing PEPCK and G6Pase transcription. TIPARP overexpression reproduced TCDD effects while TIPARP silencing diminished them.\",\n      \"method\": \"TIPARP overexpression and siRNA knockdown in hepatic cells, glucose output assay, NAD+ measurement, qPCR, western blot\",\n      \"journal\": \"Journal of Biological Chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — gain- and loss-of-function with multiple biochemical readouts in same study\",\n      \"pmids\": [\"20876576\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"TCDD-induced TIPARP directly ADP-ribosylates PEPCK (both cytosolic and mitochondrial forms), identifying ADP-ribosylation as a novel post-translational modification of PEPCK downstream of AHR activation.\",\n      \"method\": \"In vitro ADP-ribosylation assay, immunoprecipitation of ADP-ribosylated proteins from TCDD-treated cells\",\n      \"journal\": \"Journal of Biological Chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct biochemical assay but single laboratory\",\n      \"pmids\": [\"23770670\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"TIPARP mono-ADP-ribosylates AHR (but not ARNT/AHR nuclear translocator); this ADP-ribosylation promotes AHR degradation. The de-ADP-ribosylase MACROD1 (but not MACROD2) reverses TIPARP's repressive effect on AHR. Loss of Tiparp in mice dramatically increases sensitivity to dioxin-induced steatohepatitis and lethality.\",\n      \"method\": \"In vitro ADP-ribosylation assay with AHR and ARNT substrates, MACROD1/2 rescue experiments, Tiparp−/− mouse model with TCDD challenge\",\n      \"journal\": \"Journal of Biological Chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — in vitro substrate identification, macrodomain rescue, and in vivo KO model with defined phenotype\",\n      \"pmids\": [\"25975270\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"TIPARP mono-ADP-ribosylates LXRα and LXRβ and acts as a co-activator of LXR transcriptional activity; the zinc-finger and catalytic domains are required. TIPARP interacts with LXRs via an N-terminal sequence (aa 209–236). MACROD1 (not MACROD2) interacts with LXRs in a TIPARP-dependent manner and prevents the TIPARP-dependent increase in LXR activity.\",\n      \"method\": \"In vitro ADP-ribosylation assay, reporter gene assay, co-immunoprecipitation, peptide array, immunofluorescence co-localization, Tiparp−/− MEFs and mice\",\n      \"journal\": \"Biochemical Journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — multiple orthogonal methods (in vitro ribosylation, Co-IP, mutagenesis, KO cells/mice) in a single study\",\n      \"pmids\": [\"26814197\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Parp7 occupies key pluripotency gene loci (Nanog, Pou5f1, Sox2, Stella, Tet1, Zfp42) in embryonic stem cells; loss of Parp7 (or inhibition of ADP-ribosylating activity) decreases ground-state pluripotency and increases propensity to differentiate, placing Parp7 at the genetic-epigenetic interface of pluripotency networks.\",\n      \"method\": \"ChIP-seq, Parp1/Parp7 KO ES cells, inhibitor treatment, pluripotency marker analysis\",\n      \"journal\": \"Nucleic Acids Research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — ChIP-seq occupancy plus KO phenotype with multiple pluripotency readouts\",\n      \"pmids\": [\"25034692\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Nuclear localization of TIPARP depends on a short N-terminal sequence and its zinc-finger domain. The minimum catalytically active region spans aa 400–657. TIPARP activity is sensitive to iodoacetamide and hydroxylamine (implicating cysteines and acidic residues as acceptors). Mass spectrometry and ETD identified cysteine 39 as an auto-ADP-ribosylation site. TIPARP mono-ADP-ribosylates AHR at multiple peptides. Both catalytic activity and zinc-finger domain are required for AHR repression in cells.\",\n      \"method\": \"Deletion mutagenesis, in vitro ADP-ribosylation assay, chemical sensitivity assays (MIBG, iodoacetamide, hydroxylamine), mass spectrometry with ETD fragmentation, subcellular fractionation/immunofluorescence\",\n      \"journal\": \"Biochemical Journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro biochemistry with mutagenesis and MS-based site mapping\",\n      \"pmids\": [\"30373764\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Hepatocyte-specific deletion of TIPARP (Tiparpfl/fl CreAlb mice) is sufficient to increase sensitivity to dioxin-induced steatohepatitis and lethality, demonstrating that TIPARP acts as a negative regulator of AHR in hepatocytes. Tiparp-null mice show augmented AHR target gene expression and altered lipid/amino acid metabolism.\",\n      \"method\": \"Conditional Cre-lox knockout mouse model, TCDD challenge, histology, serum ALT, RNA-seq, metabolomics\",\n      \"journal\": \"Toxicological Sciences\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — tissue-specific KO with mechanistic AHR readouts and metabolomics\",\n      \"pmids\": [\"29873790\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"TiPARP forms ADP-ribosylation-dependent nuclear condensates/nuclear bodies that recruit HIF-1α and the E3 ubiquitin ligase HUWE1, promoting ubiquitination and proteasomal degradation of HIF-1α. Similarly, TiPARP promotes degradation of c-Myc and estrogen receptor, establishing TiPARP as a negative-feedback regulator of multiple oncogenic transcription factors.\",\n      \"method\": \"Live-cell imaging of nuclear condensates, co-immunoprecipitation, ubiquitination assay, proteasome inhibitor experiments, xenograft mouse models\",\n      \"journal\": \"PNAS\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — Co-IP, ubiquitination assay, condensate imaging, and in vivo xenograft with multiple substrates\",\n      \"pmids\": [\"32482854\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"PARP7 is a negative regulator of nucleic acid sensing in tumor cells; its inhibition restores type I interferon (IFN) signaling responses to nucleic acids, directly inhibits cancer cell proliferation, and activates antitumor immunity. The mechanism is dependent on inducing type I IFN signaling in tumor cells, and antitumor effects require STING pathway and TBK1 activity.\",\n      \"method\": \"PARP7 inhibitor (RBN-2397) in cancer cell lines and mouse models (xenograft and syngeneic), IFN pathway reporter assays, immune cell depletion experiments\",\n      \"journal\": \"Cancer Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — pharmacologic inhibition plus in vivo models with immune-dependency epistasis\",\n      \"pmids\": [\"34375612\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"PARP-13 (ZAP), a critical antiviral innate immune regulator, is a major substrate of PARP-7-mediated MARylation; PARP-7 preferentially MARylates PARP-13 on cysteine residues within its RNA-binding zinc-finger domain. Proteome-wide analysis reveals cysteine as the predominant MARylation acceptor for PARP-7.\",\n      \"method\": \"Chemical genetics (analog-sensitive PARP-7), proximity labeling, proteome-wide ADP-ribosylation site profiling by mass spectrometry\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — chemical genetics plus MS-based proteome-wide site mapping with orthogonal methods\",\n      \"pmids\": [\"33475084\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"PARP-7 MARylates α-tubulin to promote microtubule instability in ovarian cancer cells, regulating cancer cell growth and motility. PARP-7 substrates were identified using an NAD+ analog-sensitive approach coupled with mass spectrometry.\",\n      \"method\": \"NAD+ analog-sensitive PARP-7 coupled with mass spectrometry, cell growth/migration assays with PARP-7 depletion, gene expression analysis\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — analog-sensitive chemical genetics plus MS substrate identification and functional readout\",\n      \"pmids\": [\"33475085\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"PARP7 mono-ADP-ribosylates estrogen receptor α (ERα); the modification is mapped by mass spectrometry to peptides in the ligand-independent transactivation domain, and the ERα hinge region is required for PARP7-dependent MARylation. PARP7 overexpression reduces ligand-dependent ERα signaling; PARP7 KO MCF-7 cells show increased ERα target gene expression and proliferation.\",\n      \"method\": \"Co-immunoprecipitation, mass spectrometry, truncated ERα variant experiments, PARP7 KO cells (CRISPR), reporter assays\",\n      \"journal\": \"Cells\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — Co-IP with MS site mapping plus KO functional validation\",\n      \"pmids\": [\"33799807\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"PARP7 protein stability is regulated post-transcriptionally by androgen signaling: PARP7 has an extremely short half-life (~4.5 min) that is extended to ~25.6 min by androgen/AR signaling in prostate cancer cells. Androgen-dependent stabilization leads to nuclear accumulation of PARP7. Mutations in the catalytic domain, zinc-finger, or WWE domains each reduce the degradation rate of PARP7.\",\n      \"method\": \"Cycloheximide chase assay, androgen treatment, domain-mutation analysis, subcellular fractionation\",\n      \"journal\": \"Cells\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — direct protein stability measurement with mutagenesis and androgen manipulation\",\n      \"pmids\": [\"33572475\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"PARP7 mono-ADP-ribosylates the androgen receptor (AR) in an agonist-conformation- and nuclear-localization-dependent manner. The PARP7 Cys3His1 zinc finger (ZF) is critical for AR ADP-ribosylation and for PARP7 nuclear import; ZF mutations abrogate PARP7 enhancement of AR-dependent transcription of MYBPC1 without reducing catalytic activity or AR binding.\",\n      \"method\": \"In vitro ADP-ribosylation assay, ZF mutagenesis, nuclear import assays, reporter gene assay, AR conformation mutants\",\n      \"journal\": \"Biochemical Journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — in vitro biochemistry with domain mutagenesis and conformation-dependence experiments\",\n      \"pmids\": [\"34264286\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"CUL4B (E3 ubiquitin ligase) and TiPARP cooperate to promote TCDD-activated AHR nuclear export and proteasomal degradation; knockdown of TiPARP in CUL4B-null MEFs completely abolished AHR degradation after TCDD, demonstrating that TiPARP is required for AHR nuclear export downstream of CUL4B.\",\n      \"method\": \"MEF cell lines with CUL4B deletion and TiPARP siRNA knockdown, AHR protein level/localization assay, AHR transcriptional activity measurement\",\n      \"journal\": \"Journal of Biological Chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — epistasis using double KO/KD with defined molecular phenotype (AHR export/degradation)\",\n      \"pmids\": [\"34146543\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Loss of TIPARP catalytic activity (H532A knock-in mouse) increases sensitivity to TCDD-induced hepatotoxicity and lethality to the same degree as full TIPARP loss, confirming that the ADP-ribosyltransferase activity of TIPARP is the mechanistic basis for its AHR repressor function in vivo.\",\n      \"method\": \"Catalytic mutant knock-in mouse (TiparpH532A), TCDD challenge, RNA-seq, histology, ALT measurements\",\n      \"journal\": \"Toxicological Sciences\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — catalytic-mutant knock-in mouse with in vivo phenotype identical to KO\",\n      \"pmids\": [\"34129049\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"PARP7 MARylates the AP-1 transcription factor FRA1 on cysteine C97; this modification protects FRA1 from proteasomal degradation via PSMC3. Loss of FRA1 ADP-ribosylation (by PARP7 inhibition or C97 mutation) promotes IRF1- and IRF3-dependent cytokine and proapoptotic gene expression, culminating in CASP8-mediated apoptosis.\",\n      \"method\": \"PARP7 inhibitor (RBN-2397), site-directed mutagenesis of FRA1 C97, co-immunoprecipitation, proteasome inhibition, gene expression analysis\",\n      \"journal\": \"PNAS\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — site-specific mutagenesis of substrate, proteasome assay, and downstream pathway analysis\",\n      \"pmids\": [\"38011562\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Loss of Tiparp in mice causes aberrant cortical layering, particularly increased cell density in upper cortical layers with predominant effects on GABAergic neuron distribution, reduced neural progenitor cell proliferation, and slower neural stem cell migration. α-tubulin mono-ADP-ribosylation levels are reduced in Tiparp−/− cells, suggesting TIPARP MARylates α-tubulin during cortical development.\",\n      \"method\": \"Tiparp−/− mouse histological analysis, cell counting, neural stem cell migration assay, MAR-tubulin detection\",\n      \"journal\": \"eNeuro\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — KO mouse with defined cellular phenotype plus biochemical MAR-tubulin measurement, single study\",\n      \"pmids\": [\"31704703\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"AHR loss was identified as a mechanism of resistance to PARP7 inhibitor RBN-2397 via a genome-wide CRISPR screen; multiple cohesin complex components also modulate RBN-2397 response. AHR activators and inhibitors modulate cellular response to PARP7 inhibition, establishing AHR as a key determinant of PARP7 inhibitor sensitivity.\",\n      \"method\": \"Genome-wide CRISPR screen, AHR modulator experiments\",\n      \"journal\": \"Molecular Cancer Therapeutics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genome-wide CRISPR epistasis screen, validated with AHR modulators\",\n      \"pmids\": [\"35439318\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"PARP7 catalytic activity regulates its own protein levels (autoMARylation promotes instability); treatment with PARP7 inhibitors increases PARP7 protein levels in cells, and this increase correlates with the magnitude of type I interferon gene expression.\",\n      \"method\": \"PARP7 inhibitor treatment (KMR-206 and RBN-2397), western blot for PARP7 protein levels, IFN-β reporter assays\",\n      \"journal\": \"Cell Chemical Biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — pharmacological inhibition with protein level quantification, replicated with two structurally distinct inhibitors\",\n      \"pmids\": [\"36529140\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"PARP7 inhibits type I IFN production by directly interacting with IRF3 through its catalytic domain and disrupting the IRF3:CBP/p300 transcriptional holocomplex required for IFN-I production. This is MARylation-dependent. Irf3−/− or transcription-defective Irf3S1/S1 or Sting−/− rescues Parp7H532A/H532A autoimmunity and lung disease, placing PARP7 upstream of IRF3 and STING.\",\n      \"method\": \"Parp7−/− and Parp7H532A/H532A mice, genetic epistasis with Irf3−/−/Irf3S1/S1/Sting−/− rescue, Co-IP of PARP7-IRF3 and IRF3-CBP/p300, MARylation assays\",\n      \"journal\": \"Journal of Experimental Medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — MARylation-dependent mechanism established by catalytic mutant knock-in plus genetic epistasis with multiple pathway components\",\n      \"pmids\": [\"39969510\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"PARP7 generates an ADP-ribosyl degron on the DNA-binding domain of AR (chromatin-bound AR), which is recognized by the ADP-ribose reader domain of the E3 ubiquitin ligase DTX2, leading to non-conventional ubiquitin conjugation to ADP-ribosyl-cysteine and proteasomal degradation of AR. Mathematical modeling and an AR DNA-binding mutant confirmed that PARP7 preferentially ADP-ribosylates chromatin-bound AR.\",\n      \"method\": \"Mathematical modeling, AR DNA-binding mutant rescue, DTX2 reader domain binding assay, in vitro ubiquitination assay, mass spectrometry\",\n      \"journal\": \"EMBO Journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — reconstituted degradation pathway with substrate mutant validation and mathematical modeling\",\n      \"pmids\": [\"40681873\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"PARP7 functions as a nuclear NAD+ sensor: at higher nuclear NAD+ concentrations (in undifferentiated preadipocytes), PARP7 is catalytically active for autoMARylation; as NAD+ declines upon differentiation, autoMARylation decreases. AutoMARylation promotes PARP7 instability via the E3 ligases DTX2 and RNF114 through the ubiquitin-proteasome pathway. Stabilized PARP7 serves as a coregulator of C/EBPβ by stimulating p300-mediated H3K27ac and C/EBPβ genome-wide binding.\",\n      \"method\": \"NAD+ measurement in preadipocytes vs adipocytes, in vitro autoMARylation assay, DTX2/RNF114 Co-IP/ubiquitination assay, ChIP-seq for C/EBPβ and H3K27ac, PARP7 KO mouse model with fat-pad analysis\",\n      \"journal\": \"Cell Reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — in vitro biochemistry with ChIP-seq and KO mouse model confirming multiple mechanistic steps\",\n      \"pmids\": [\"41621069\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"PARP7 is a proteotoxic stress sensor: during proteotoxic stress PARP7 is stabilized and MARylates substrates that accumulate in cytoplasmic foci containing ubiquitin and p62, subsequently trafficked to aggresomes and degraded by autophagy. Ubiquitination is required for this process. PARP7 inhibition impedes accumulation of MARylated proteins during stress.\",\n      \"method\": \"PARP7 inhibitor treatment during proteotoxic stress, immunofluorescence for aggresome markers, ADP-ribosylation detection, ubiquitination pathway blockade\",\n      \"journal\": \"EMBO Journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — pharmacological inhibition with imaging and biochemical readouts, single study\",\n      \"pmids\": [\"40836037\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"p300 and CBP are direct nuclear PARP7 substrates; PARP7 contains an α-helical domain essential for p300/CBP interaction, MARylation, and their proteasomal degradation. Disrupting PARP7–p300/CBP interaction prevents PARP7's suppression of IFNβ. PARP7 inhibitors induce IFNβ via two mechanisms: inhibiting MARylation of p300/CBP (loss-of-function) and stabilizing the PARP7–p300/CBP complex (gain-of-function).\",\n      \"method\": \"Analog-sensitive chemical genetic approach, Co-IP, domain deletion mutagenesis, proteasome inhibition, IFNβ reporter assay\",\n      \"journal\": \"bioRxiv (preprint)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1–2 — chemical genetics plus mutagenesis and functional readout, but preprint not yet peer-reviewed\",\n      \"pmids\": [\"40631120\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"DTX2 is the E3 ligase responsible for degrading ADP-ribosylated PARP7, AHR, and other PARP7 substrates; mono-ADP-ribosylation by PARP7 acts as a degradation mark. Blocking the ubiquitin/proteasome pathway reveals high levels of endogenous ADP-ribosylation by PARP7 on PARP7 itself and AHR.\",\n      \"method\": \"Ubiquitin pathway blockade, mass spectrometry identification of ADP-ribosylated substrates, DTX2 KO/knockdown, Co-IP\",\n      \"journal\": \"EMBO Journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — endogenous substrate identification under physiological conditions with E3 ligase genetic validation\",\n      \"pmids\": [\"41326691\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"TIPARP interacts with EIF3B (eukaryotic translation initiation factor 3 subunit B) through nucleoplasmic redistribution, leading to mitochondrial dysfunction. Knockdown of Tiparp or inhibition with a TIPARP inhibitor (XG-04-B1) restores mitochondrial homeostasis in ischemic stroke mice. EIF3B is identified as a direct target of TIPARP.\",\n      \"method\": \"Co-immunoprecipitation/interaction assay, Tiparp knockdown and inhibitor treatment in ischemic stroke mouse model, mitochondrial function assays\",\n      \"journal\": \"Pharmacological Research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 — Co-IP substrate identification plus KD/inhibitor phenotype, single study\",\n      \"pmids\": [\"39547463\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"METTL16 directly binds TIPARP mRNA and enhances its m6A modification, thereby stabilizing TIPARP transcripts and upregulating TIPARP protein expression. This METTL16-m6A-TIPARP axis promotes cerebral ischemia-reperfusion injury; TIPARP overexpression abolishes protective effects of METTL16 knockdown.\",\n      \"method\": \"RIP assay, m6A-RIP-qPCR, cycloheximide chase for protein stability, MCAO mouse model, rescue experiments with TIPARP overexpression\",\n      \"journal\": \"International Journal of General Medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — RIP and m6A-RIP directly demonstrate METTL16 binding and m6A modification of TIPARP mRNA with in vivo rescue\",\n      \"pmids\": [\"42004240\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"AHR directly regulates TIPARP expression by binding to two genomic regions containing multiple AHR response elements (AHREs) at the TIPARP promoter; AHR also co-regulates TIPARP-AS1, a cis long non-coding RNA upstream of TIPARP exon 1, via a proximal AHRE cluster.\",\n      \"method\": \"Reporter gene and deletion assays, ChIP for AHR at TIPARP promoter, qPCR for TIPARP and TIPARP-AS1\",\n      \"journal\": \"Biochemical and Biophysical Research Communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — ChIP plus reporter/deletion experiments, single laboratory\",\n      \"pmids\": [\"29274782\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"TIPARP/PARP7 is a nuclear mono-ADP-ribosyltransferase (MARylase) that uses NAD+ to transfer single ADP-ribose moieties preferentially onto cysteine residues of diverse substrate proteins—including AHR, LXRα/β, ERα, AR (on chromatin), FRA1, PARP-13, α-tubulin, p300/CBP, and PEPCK—creating an ADP-ribosyl degron recognized by ubiquitin E3 ligases (DTX2, RNF114, HUWE1) that targets substrates for proteasomal degradation; its auto-MARylation activity is tuned by nuclear NAD+ concentration (sensor function), promotes its own rapid proteasomal turnover, and the enzyme's catalytic and zinc-finger domains together mediate nuclear localization, substrate ADP-ribosylation, and transcriptional repression of AHR and type I interferon signaling, establishing TIPARP as a negative-feedback regulator of AHR, estrogen, androgen, and innate immune signaling pathways.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"TIPARP (PARP7) is a nuclear mono-ADP-ribosyltransferase that transfers single ADP-ribose units preferentially onto cysteine residues of diverse substrate proteins—including AHR, AR, ERα, LXRα/β, FRA1, PARP-13, α-tubulin, HIF-1α, p300/CBP, and PEPCK—thereby tagging them for recognition by ADP-ribose-reading E3 ubiquitin ligases (DTX2, RNF114, HUWE1) and subsequent proteasomal degradation [PMID:23275542, PMID:25975270, PMID:40681873, PMID:41326691, PMID:32482854]. This ADP-ribosyl degron mechanism establishes TIPARP as a negative-feedback repressor of AHR, estrogen receptor, and type I interferon signaling; in the interferon pathway, TIPARP MARylates IRF3 and disrupts the IRF3–CBP/p300 transcriptional complex required for IFN-β production, and genetic loss of IRF3 or STING rescues the autoimmune phenotype of catalytic-dead Parp7 knock-in mice [PMID:39969510, PMID:34375612, PMID:38011562]. TIPARP also functions as a nuclear NAD⁺ sensor: high NAD⁺ promotes autoMARylation that drives its own rapid proteasomal turnover (~4.5 min half-life), while declining NAD⁺ stabilizes the protein, enabling it to act as a transcriptional coregulator—for example, stimulating p300-mediated H3K27 acetylation and C/EBPβ chromatin binding during adipogenesis [PMID:41621069, PMID:33572475]. In vivo, Tiparp knockout or catalytic-dead knock-in mice exhibit dramatically increased sensitivity to dioxin-induced steatohepatitis, aberrant cortical neuronal layering, and spontaneous type I interferon–driven autoimmunity, underscoring the enzyme's essential homeostatic roles [PMID:25975270, PMID:34129049, PMID:31704703, PMID:39969510].\",\n  \"teleology\": [\n    {\n      \"year\": 2010,\n      \"claim\": \"Before TIPARP's enzymatic activity toward specific substrates was defined, this study revealed that TCDD-induced TIPARP consumes NAD⁺ to suppress hepatic gluconeogenesis by reducing SIRT1 activity and destabilizing PGC1α, establishing TIPARP as a metabolically active ADP-ribosyltransferase with physiological consequences.\",\n      \"evidence\": \"TIPARP overexpression and siRNA knockdown in hepatic cells with NAD⁺ measurement and glucose output assays\",\n      \"pmids\": [\"20876576\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct ADP-ribosylation of PGC1α not shown\", \"In vivo hepatic glucose phenotype not tested\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"The central question of what TIPARP does enzymatically was answered: TIPARP is a mono-ADP-ribosyltransferase that auto-ribosylates and ribosylates histones, interacts directly with AHR, and represses AHR transcriptional activity through a negative feedback loop requiring both the zinc-finger and catalytic domains.\",\n      \"evidence\": \"In vitro ADP-ribosylation assay, Co-IP, ChIP at CYP1A1, reporter assay with domain mutants, KO MEFs\",\n      \"pmids\": [\"23275542\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"AHR residues modified by TIPARP not mapped\", \"Mechanism of AHR degradation (proteasomal vs other) not resolved\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"PEPCK was identified as a direct ADP-ribosylation substrate of TIPARP, extending the enzyme's substrate repertoire beyond AHR to metabolic enzymes.\",\n      \"evidence\": \"In vitro ADP-ribosylation assay and immunoprecipitation from TCDD-treated cells\",\n      \"pmids\": [\"23770670\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional consequence of PEPCK MARylation on enzyme activity not determined\", \"Single laboratory finding\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"TIPARP was placed at the genetic-epigenetic interface of pluripotency: Parp7 occupies key pluripotency loci and its loss decreases ground-state pluripotency, revealing a role beyond xenobiotic defense.\",\n      \"evidence\": \"ChIP-seq in embryonic stem cells, Parp7 KO ES cells, pluripotency marker analysis\",\n      \"pmids\": [\"25034692\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct substrates at pluripotency loci not identified\", \"Whether catalytic activity or scaffolding drives the pluripotency effect is unclear\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"The AHR feedback mechanism was sharpened: TIPARP directly MARylates AHR (not ARNT), this modification promotes AHR degradation, the de-MARylase MACROD1 reverses the modification, and Tiparp-null mice exhibit extreme dioxin sensitivity, validating the pathway in vivo.\",\n      \"evidence\": \"In vitro ADP-ribosylation with AHR/ARNT, MACROD1/2 rescue, Tiparp⁻/⁻ mouse TCDD challenge\",\n      \"pmids\": [\"25975270\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"AHR modification sites not mapped\", \"Whether MACROD1 acts on AHR in vivo not tested\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"TIPARP's substrate repertoire was extended to nuclear receptors LXRα/β, where it acts as a co-activator rather than repressor, demonstrating context-dependent transcriptional outcomes of MARylation.\",\n      \"evidence\": \"In vitro ADP-ribosylation, reporter assay, Co-IP, Tiparp⁻/⁻ MEFs and mice\",\n      \"pmids\": [\"26814197\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"LXR MARylation sites not mapped\", \"Whether LXR MARylation leads to degradation or activation in vivo unclear\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"The catalytic architecture and amino acid specificity were defined: cysteine 39 was identified as an auto-MARylation site by mass spectrometry, cysteine and acidic residues serve as acceptors, the minimal catalytic region spans aa 400–657, and nuclear localization requires the N-terminal sequence and zinc-finger domain.\",\n      \"evidence\": \"Deletion mutagenesis, chemical sensitivity assays, ETD mass spectrometry, subcellular fractionation\",\n      \"pmids\": [\"30373764\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Full catalog of cysteine auto-modification sites incomplete\", \"Structural basis for cysteine preference unknown\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Hepatocyte-specific deletion confirmed the cell-autonomous role of TIPARP as an AHR repressor in liver, ruling out systemic or immune-mediated contributions to the dioxin-sensitivity phenotype.\",\n      \"evidence\": \"Conditional Tiparpᶠˡ/ᶠˡ CreAlb knockout mice, TCDD challenge, RNA-seq, metabolomics\",\n      \"pmids\": [\"29873790\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Contribution of non-hepatocyte TIPARP to systemic dioxin effects not addressed\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"TIPARP was shown to MARylate α-tubulin in the developing brain; Tiparp-null mice display aberrant cortical layering and impaired neural progenitor migration, connecting TIPARP's cytoskeletal substrate to a neurodevelopmental phenotype.\",\n      \"evidence\": \"Tiparp⁻/⁻ mouse brain histology, neural stem cell migration assay, MAR-tubulin detection\",\n      \"pmids\": [\"31704703\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Tubulin modification sites not mapped in vivo\", \"Single study without independent replication\", \"Causal link between tubulin MARylation and migration phenotype not formally tested\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"TIPARP was found to form ADP-ribosylation-dependent nuclear condensates that recruit HUWE1 E3 ligase and promote proteasomal degradation of HIF-1α, c-Myc, and estrogen receptor, establishing a general condensate-based degradation mechanism for oncogenic transcription factors.\",\n      \"evidence\": \"Live-cell imaging, Co-IP, ubiquitination assay, proteasome inhibitor, xenograft models\",\n      \"pmids\": [\"32482854\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Liquid-liquid phase separation properties not biophysically characterized\", \"Whether condensate formation is required for all substrates unclear\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Multiple parallel discoveries in 2021 dramatically expanded the substrate landscape and functional contexts: PARP-13/ZAP and α-tubulin were identified as major substrates by proteome-wide chemical genetics, confirming cysteine as the predominant acceptor; ERα and AR were shown to be MARylated with functional consequences for hormone-dependent transcription; PARP7 protein half-life was measured at ~4.5 min and is extended by androgen signaling; CUL4B was shown to cooperate with TIPARP for AHR export/degradation; a catalytic-dead knock-in mouse phenocopied the full knockout; and pharmacological PARP7 inhibition restored type I IFN signaling via the STING/TBK1 pathway to suppress tumor growth.\",\n      \"evidence\": \"Chemical genetics with analog-sensitive PARP7, proteome-wide MS, CRISPR KO cells, cycloheximide chase, catalytic-mutant knock-in mice, PARP7 inhibitor in syngeneic tumor models with immune depletion\",\n      \"pmids\": [\"33475084\", \"33475085\", \"33799807\", \"33572475\", \"34264286\", \"34146543\", \"34129049\", \"34375612\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Complete cellular MARylome of PARP7 under physiological conditions not catalogued\", \"Structural basis for substrate selectivity unresolved\", \"Relative contributions of different E3 ligases to different substrates unclear\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Auto-MARylation was established as a self-destabilizing mechanism: PARP7 inhibitors increase PARP7 protein levels, and this stabilization correlates with IFN induction. AHR loss was identified as a resistance mechanism to PARP7 inhibitors via genome-wide CRISPR screening.\",\n      \"evidence\": \"Two structurally distinct PARP7 inhibitors with western blot quantification; genome-wide CRISPR screen with AHR modulator validation\",\n      \"pmids\": [\"36529140\", \"35439318\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"E3 ligase responsible for MARylation-dependent PARP7 turnover not identified in these studies\", \"Whether AHR-independent mechanisms of inhibitor sensitivity exist\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Site-specific MARylation of FRA1 at cysteine C97 was shown to protect FRA1 from PSMC3-mediated proteasomal degradation; loss of this modification upon PARP7 inhibition activates IRF1/IRF3-dependent apoptosis, providing a molecular mechanism for PARP7 inhibitor antitumor activity.\",\n      \"evidence\": \"PARP7 inhibitor, FRA1 C97 mutagenesis, Co-IP with PSMC3, gene expression and apoptosis assays\",\n      \"pmids\": [\"38011562\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether FRA1 stabilization is the dominant antitumor mechanism or one of several parallel pathways\", \"PSMC3 interaction mechanism not structurally resolved\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"The type I IFN suppression mechanism was resolved at the molecular level: PARP7 MARylates substrates in the IRF3–CBP/p300 axis to disrupt the transcriptional holocomplex required for IFN-β, and genetic epistasis with Irf3⁻/⁻, Irf3ˢ¹/ˢ¹, and Sting⁻/⁻ rescues autoimmunity in catalytic-dead mice, definitively placing PARP7 upstream of IRF3/STING.\",\n      \"evidence\": \"Parp7H532A/H532A mice crossed with Irf3⁻/⁻, Irf3ˢ¹/ˢ¹, Sting⁻/⁻; Co-IP of PARP7–IRF3 and IRF3–CBP/p300\",\n      \"pmids\": [\"39969510\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Specific IRF3 cysteine residues MARylated not mapped\", \"Whether PARP7 also acts on downstream effectors (e.g. ISG products) independently of IRF3\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"The ADP-ribosyl degron concept was biochemically reconstituted: PARP7 MARylates chromatin-bound AR on its DNA-binding domain, creating a degron recognized by DTX2's ADP-ribose reader domain, leading to non-canonical ubiquitin conjugation to ADP-ribosyl-cysteine and proteasomal degradation. DTX2 was also identified as the E3 ligase for PARP7 itself and AHR.\",\n      \"evidence\": \"Mathematical modeling, AR DNA-binding mutant rescue, DTX2 reader domain binding, in vitro ubiquitination, MS; DTX2 KO/KD with endogenous substrate validation\",\n      \"pmids\": [\"40681873\", \"41326691\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether DTX2 is the universal reader for all PARP7-generated degrons or specific to AR/AHR substrates\", \"Structural details of DTX2 recognition of ADP-ribosyl-cysteine unknown\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"PARP7 was established as a nuclear NAD⁺ sensor: fluctuations in nuclear NAD⁺ tune auto-MARylation and thereby protein stability, which in turn regulates C/EBPβ-dependent adipogenesis by promoting p300-mediated H3K27 acetylation.\",\n      \"evidence\": \"NAD⁺ measurement in preadipocytes/adipocytes, in vitro autoMARylation, DTX2/RNF114 ubiquitination assay, ChIP-seq, PARP7 KO mouse fat analysis\",\n      \"pmids\": [\"41621069\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether NAD⁺ sensing is specific to adipogenesis or generalizable\", \"Quantitative relationship between NAD⁺ concentration and PARP7 activity not modeled\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"PARP7 was identified as a proteotoxic stress sensor that stabilizes under stress to MARylate substrates routed to aggresomes via ubiquitin and p62 for autophagic clearance, revealing a cytoplasmic quality-control function.\",\n      \"evidence\": \"PARP7 inhibitor during proteotoxic stress, aggresome marker immunofluorescence, ADP-ribosylation detection\",\n      \"pmids\": [\"40836037\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single study; identity of MARylated stress substrates not determined\", \"Whether aggresome routing requires DTX2 or other specific E3 ligases unknown\", \"Mechanism of PARP7 stabilization under proteotoxic stress not defined\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"A complete structural model of PARP7 explaining cysteine substrate selectivity, zinc-finger-mediated substrate recognition, and the interplay between nuclear condensate formation and degron-dependent degradation remains to be determined.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No crystal or cryo-EM structure of full-length PARP7 or PARP7–substrate complex\", \"Complete in vivo cysteine MARylome not catalogued\", \"Relative contributions of DTX2, RNF114, and HUWE1 to different substrates not systematically compared\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0016740\", \"supporting_discovery_ids\": [0, 2, 3, 4, 6, 10, 11, 12, 14, 17, 22, 23]},\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [0, 3, 10, 11, 12, 14, 22]},\n      {\"term_id\": \"GO:0140110\", \"supporting_discovery_ids\": [0, 4, 5, 8, 21, 23]},\n      {\"term_id\": \"GO:0140299\", \"supporting_discovery_ids\": [23]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [0, 6, 8, 13, 14, 23]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0, 3, 9, 21]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [9, 10, 17, 21]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 3, 4, 8, 9, 12, 14, 21, 22]},\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [0, 8, 13, 22, 23, 26]},\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [1, 2, 23]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [17]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [5, 18]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"AHR\",\n      \"DTX2\",\n      \"RNF114\",\n      \"HUWE1\",\n      \"IRF3\",\n      \"MACROD1\",\n      \"CUL4B\",\n      \"EP300\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}