{"gene":"RBL1","run_date":"2026-06-10T06:43:36","timeline":{"discoveries":[{"year":1991,"finding":"p107 (RBL1) was cloned and shown to contain a major region of RB homology (~564 residues) that constitutes a 'pocket' domain capable of independently binding SV40 large T antigen and adenovirus E1A. The unique spacer sequence between the A and B sub-segments of the p107 pocket distinguishes it from RB.","method":"cDNA cloning, sequence analysis, binding assays with T antigen and E1A","journal":"Cell","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct biochemical binding assays combined with sequence/domain analysis, foundational paper replicated by multiple subsequent studies","pmids":["1833063"],"is_preprint":false},{"year":1992,"finding":"p107 forms a cell cycle-regulated complex with E2F and cyclin A during S phase, distinct from the G1-phase RB–E2F complex. This S-phase complex also contains p33cdk2.","method":"Co-immunoprecipitation, gel mobility shift assay, cell cycle fractionation","journal":"Cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP across multiple labs in the same year (PMID 1531040, 1530885, 1532457, 1532458), independently replicated","pmids":["1531040","1530885","1532457","1532458"],"is_preprint":false},{"year":1992,"finding":"Cyclin A binds directly to the p107 pocket domain (specifically the unique spacer sequence between the A and B sub-segments) in the absence of viral oncoproteins; this interaction does not occur with the RB pocket.","method":"In vitro binding assay, domain mapping with pocket mutants","journal":"Science","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct in vitro binding assay with domain mutants, replicated by independent laboratory (PMID 1532458)","pmids":["1532457","1532458"],"is_preprint":false},{"year":1992,"finding":"Cyclin E and its associated cdk2 form a complex with E2F and p107 specifically during G1, whereas the cyclin A/cdk2/p107/E2F complex is S-phase specific, demonstrating temporally distinct cyclin partnerships for p107.","method":"Immunoprecipitation with cyclin E-specific antisera, cell cycle synchronization","journal":"Genes & development","confidence":"High","confidence_rationale":"Tier 2 / Strong — specific antisera immunoprecipitation across cell cycle phases, replicated in subsequent studies","pmids":["1398067"],"is_preprint":false},{"year":1993,"finding":"p107 is a potent inhibitor of E2F-mediated transactivation; overexpression of p107 arrests sensitive cells in G1. Growth arrest by p107 and pRB is rescued differentially by cell cycle regulators, and certain p107 mutants unable to associate with E1A still inhibit proliferation, indicating mechanistic differences from pRB.","method":"Transient transfection, reporter assay, cell proliferation assay, flow cytometry","journal":"Genes & development","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal functional assays (transcription, proliferation, cell cycle), independently confirmed by other groups","pmids":["8319904"],"is_preprint":false},{"year":1993,"finding":"p107 inhibits E2F-dependent transcription in a co-transfection assay, and this repression correlates with the appearance of p107-containing E2F complexes at the G1/S transition rather than earlier in G1 like RB.","method":"Co-transfection reporter assay, EMSA, co-immunoprecipitation","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 2 / Strong — reporter assay plus EMSA plus Co-IP in same study, replicated across labs","pmids":["8458319"],"is_preprint":false},{"year":1993,"finding":"p107 associates in vivo with cyclin A, cyclin E, cdk2, and a 62–65 kDa E2F-like phosphoprotein (subsequently identified as E2F-4) that is immunologically distinct from pRB-associated E2F-1.","method":"Monoclonal antibody immunoprecipitation, biochemical characterization","journal":"Journal of virology","confidence":"High","confidence_rationale":"Tier 2 / Strong — panel of monoclonal antibodies, multiple Co-IPs, replicated by parallel studies","pmids":["8230483"],"is_preprint":false},{"year":1993,"finding":"p107 functions as a general transcriptional repressor when tethered to a promoter via E2F, and this repression is overcome by adenovirus E1A. Repression is cell-type-specific (absent in F9 embryonal carcinoma cells, present in differentiated derivatives).","method":"Transient co-transfection reporter assay, Gal4 fusion constructs","journal":"Molecular biology of the cell","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reporter assay with Gal4-tethering approach, single lab, two methods","pmids":["7685208"],"is_preprint":false},{"year":1993,"finding":"HPV16 E7 binds p107 in vivo through sequences overlapping but not identical to the RB-binding region, and this interaction is associated with a histone H1 kinase activity restricted to G2/M phase.","method":"Co-immunoprecipitation, kinase assay, E7 point mutant analysis","journal":"Journal of virology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP plus kinase assay plus mutant analysis, single lab","pmids":["8386265"],"is_preprint":false},{"year":1994,"finding":"E2F-4 is a specific binding partner of p107 in vivo; p107 binding regulates E2F-4 transcriptional activity and suppresses the ability of E2F-4 to transform immortalized rodent cells.","method":"Co-immunoprecipitation, reporter assay, transformation assay","journal":"Genes & development","confidence":"High","confidence_rationale":"Tier 2 / Strong — two independent labs simultaneously demonstrated E2F-4/p107 association (PMID 7958925, 7958924) using Co-IP and functional assays","pmids":["7958925","7958924"],"is_preprint":false},{"year":1994,"finding":"p107 binds directly to the N-terminal transactivation domain of c-Myc in vivo and suppresses c-Myc-mediated transactivation; expression of c-Myc releases cells from p107-induced growth arrest but not pRB-induced arrest.","method":"Co-immunoprecipitation, reporter transactivation assay, cell growth rescue experiment","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo Co-IP confirmed independently (PMID 8146655 used cDNA library screen + in vivo association), two orthogonal functional assays","pmids":["8076603","8146655"],"is_preprint":false},{"year":1995,"finding":"p107 contains a p21CIP1-related cyclin/cdk2-binding domain (spacer region) that inhibits phosphorylation of target substrates by cyclin A/cdk2 and cyclin E/cdk2; binding of p107 and p21 to cyclin/cdk2 is mutually exclusive. DNA damage-elevated p21 displaces p107 from cyclin/cdk2 complexes. Activation of p107-bound cyclin/cdk kinases leads to dissociation of p107 from E2F.","method":"In vitro kinase inhibition assay, competitive binding, co-immunoprecipitation, DNA damage treatment","journal":"Genes & development","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstituted kinase assay plus mutually exclusive binding experiments plus cellular validation, multiple orthogonal methods","pmids":["7622038"],"is_preprint":false},{"year":1995,"finding":"p107 contains two independent growth suppression domains: one mediating E2F interaction and one mediating cyclin A/E-cdk2 interaction. In C33A cells, only the cyclin-binding domain is active as a growth suppressor, revealing a functional difference from pRB.","method":"Structure-function analysis with deletion mutants, co-expression growth assay","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 2 / Strong — systematic domain-deletion analysis with functional readouts in multiple cell lines, comprehensive structure-function study","pmids":["7743997"],"is_preprint":false},{"year":1995,"finding":"Cyclin D1/cdk4, but not cyclin E/cdk2, phosphorylates p107 in vivo beginning ~8 hours after serum stimulation; phosphorylation by cyclin D1/cdk4 causes loss of p107 association with E2F-4 and release of the p107-induced cell cycle block.","method":"In vivo phosphorylation assay, dominant-negative cdk4 expression, co-immunoprecipitation, cell cycle analysis","journal":"Genes & development","confidence":"High","confidence_rationale":"Tier 2 / Strong — dominant-negative approach plus biochemical phosphorylation analysis plus Co-IP, multiple orthogonal methods, independently confirmed","pmids":["7797074"],"is_preprint":false},{"year":1995,"finding":"p107 phosphorylation begins in mid-G1 via cyclin D-associated kinase activity; hypophosphorylated p107 selectively binds E2F-4, and G1 cyclin-dependent phosphorylation of p107 dissociates p107–E2F-4 complexes and inactivates p107's G1 blocking function.","method":"Cell synchronization, phosphorylation timing analysis, co-immunoprecipitation, cell cycle block assay","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — synchronized cell biochemistry plus functional G1 block assay, consistent with parallel Beijersbergen et al. findings","pmids":["8643455"],"is_preprint":false},{"year":1995,"finding":"p107's ability to suppress E2F-dependent transcription requires E2F binding but does not require association with cyclin A/cdk2; both E2F-dependent and E2F-independent events correlate with p107-mediated growth suppression.","method":"p107 mutant analysis, reporter assay, growth suppression assay","journal":"Molecular and cellular biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — mutant analysis with functional readouts, single lab, two orthogonal assays","pmids":["7799940"],"is_preprint":false},{"year":1995,"finding":"p107 associates with transcription factor Sp1 in vivo and represses Sp1-dependent transcription; this repression is mediated through a region of p107 distinct from the pocket domain required for E2F regulation.","method":"Co-immunoprecipitation from multiple cell lines, reporter assay with Gal4-Sp1 chimera, domain mapping","journal":"Molecular and cellular biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — endogenous Co-IP plus domain-specific reporter assay, single lab","pmids":["7565695"],"is_preprint":false},{"year":1995,"finding":"The p107 promoter contains tandem E2F binding sites; the retinoblastoma protein and p107 itself repress p107 promoter activity through the 5' (distal) E2F site, while the 3' (proximal, initiation-site) copy is more important for basal activity. This defines an autoregulatory loop.","method":"Promoter deletion analysis, site-directed mutagenesis, reporter assay, co-transfection","journal":"Molecular and cellular biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — mutagenesis of specific E2F sites with reporter assay, single lab","pmids":["7791762"],"is_preprint":false},{"year":1996,"finding":"E2F-4 switches from p130 (in G0/quiescence) to association with p107 and pRB as cells re-enter the cell cycle at the G1-to-S transition; E2F-1, -2, and -3 bind only pRB and are restricted to post-G1/S; E2F-4 accounts for the vast majority of endogenous E2F activity.","method":"Immunoprecipitation with specific antisera, EMSA, cell synchronization","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — systematic immunoprecipitation survey across cell cycle phases with specific antisera for each E2F/DP and pocket protein","pmids":["8657117"],"is_preprint":false},{"year":1996,"finding":"p107 and p130 have redundant roles in limb development: simultaneous genetic inactivation of both p107 and p130 causes deregulated chondrocyte growth, defective endochondral bone development, and neonatal lethality, while single knockouts are largely normal.","method":"Gene targeting in mouse, histological analysis, MEF culture analysis","journal":"Genes & development","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic epistasis via double knockout mouse, multiple tissues analyzed, phenotype replicated in independent knockout studies","pmids":["8682294"],"is_preprint":false},{"year":1996,"finding":"Targeted disruption of mouse p107 alone produces viable, fertile mice with no obvious abnormalities; combined Rb+/-;p107-/- mice show growth retardation and retinal dysplasia; Rb-/-;p107-/- embryos die ~2 days earlier than Rb-/- embryos with accelerated apoptosis in liver and CNS, demonstrating overlapping functions of p107 and Rb in vivo.","method":"Homologous recombination gene targeting, compound mutant generation, histological analysis","journal":"Genes & development","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic epistasis via compound knockout mice, multiple phenotypic readouts, independently replicated (PMID 8682294)","pmids":["8682293"],"is_preprint":false},{"year":1996,"finding":"p107 pocket domain is sufficient for E2F inactivation, general transcriptional repressor activity, and most growth suppressor activity; the A and B sub-domains of the pocket are fully functional even when expressed as separate proteins, suggesting they interact at the promoter.","method":"Deletion mutagenesis, Gal4-fusion reporter assay, co-expression growth assay","journal":"Molecular and cellular biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — systematic domain deletions with two functional readouts, single lab","pmids":["8668177"],"is_preprint":false},{"year":1997,"finding":"p107 and p130 repress RNA polymerase III transcription by directly interacting with the TFIIIB subunit of the Pol III transcription machinery; disruption by HPV E7 or genetic loss of p107/p130 deregulates Pol III activity.","method":"Transient transfection assay, pull-down with recombinant proteins, co-immunoprecipitation, cofractionation, MEFs from double-knockout mice","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct pull-down plus endogenous Co-IP plus genetic validation with double-KO fibroblasts, multiple orthogonal methods","pmids":["10330166"],"is_preprint":false},{"year":1997,"finding":"p107 and p130 use a conserved N-terminal domain (distinct from the E2F-binding pocket) to stoichiometrically inhibit cyclin A-cdk2 and cyclin E-cdk2 kinase activity in vitro; endogenous p130–cyclin A–cdk2 complexes purified from human cells display low kinase activity that is augmented upon dissociation of p130.","method":"In vitro reconstitution with purified recombinant proteins, kinase assay, purification of endogenous complexes","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution with purified components plus endogenous complex purification, mechanistically rigorous","pmids":["9199292"],"is_preprint":false},{"year":1997,"finding":"SV40 large T antigen alters the phosphorylation state of p107 and p130, requiring both the LXCXE domain (for binding) and the N-terminal J domain homology region; the J domain effect is separable from mere binding.","method":"Transient expression assay, phosphorylation state analysis, T antigen domain mutants","journal":"Journal of virology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — domain mutant analysis with phosphorylation readout, single lab","pmids":["8627752"],"is_preprint":false},{"year":1997,"finding":"The J domain of SV40 large T antigen is required to inactivate p130 and p107; a heterologous DnaJ protein J domain functionally substitutes for T antigen's N terminus in altering p107/p130 phosphorylation; J domain is dispensable in MEFs lacking both p130 and p107, placing p107/p130 as the relevant J domain targets.","method":"Domain mutant and heterologous J domain substitution, phosphorylation analysis, MEFs from p107/p130 double-KO","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic epistasis with double-KO MEFs plus heterologous J domain rescue, multiple orthogonal methods","pmids":["9271376"],"is_preprint":false},{"year":1998,"finding":"p107 loss in a pRB-deficient background (p107/pRB double-null chimeric mice) leads to retinoblastoma, providing first in vivo evidence that p107 exerts a tumor suppressor function in the retina, suppressing retinoblastoma development caused by pRB deficiency.","method":"Gene targeting, chimeric mouse generation, histopathology","journal":"Genes & development","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct genetic epistasis with tumor phenotype, independently supported by Lee et al. 1996","pmids":["9620848"],"is_preprint":false},{"year":1998,"finding":"p107 is a dual cyclin/cdk2 inhibitor with a Ki comparable to p21/WAF1; p107 harbors two cyclin-binding sites (N-terminal and C-terminal/spacer), both required for kinase inhibition. The C-terminal site is a substrate but not an inhibitor; the N-terminal site inhibits without being an efficient substrate. pRB does not inhibit cdks.","method":"In vitro kinase inhibition assay with Ki determination, domain mutant analysis, peptide competition","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — rigorous in vitro reconstitution with Ki determination plus systematic domain mutant analysis, mechanistically detailed","pmids":["9710622"],"is_preprint":false},{"year":1998,"finding":"p107 expression is transcriptionally regulated in a growth-state-dependent manner via E2F-mediated repression in quiescent cells; p130 controls p107 expression in quiescent cells, whereas p130 protein stability is posttranscriptionally controlled by proteasomal degradation upon CDK-mediated phosphorylation.","method":"Northern blot, promoter analysis, proteasome inhibitor treatment, Western blot across growth states","journal":"Cell growth & differentiation","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple methods (transcriptional vs. posttranslational) but single lab","pmids":["9563849"],"is_preprint":false},{"year":1999,"finding":"A novel PP2A regulatory subunit PR59 specifically co-immunoprecipitates with p107 (but not pRB) and promotes dephosphorylation of p107 (but not pRB) when overexpressed, causing G1 accumulation; PR59 is a genuine PP2A component that targets the catalytic subunit specifically to p107.","method":"Yeast two-hybrid (isolation), co-immunoprecipitation, dephosphorylation assay, cell cycle analysis","journal":"Oncogene","confidence":"High","confidence_rationale":"Tier 2 / Strong — Co-IP plus functional dephosphorylation assay plus cell cycle readout, multiple orthogonal methods","pmids":["9927208"],"is_preprint":false},{"year":1999,"finding":"C/EBPalpha directly interacts with p107 (co-immunoprecipitation) and disrupts S-phase-specific E2F-p107 complexes through a protein-protein interaction mediated by a short C/EBPalpha domain with E2F homology, independent of C/EBPalpha DNA binding.","method":"Co-immunoprecipitation, EMSA, bacterially expressed purified C/EBPalpha disruption assay","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — endogenous Co-IP plus in vitro disruption assay with purified protein, multiple orthogonal methods","pmids":["10082561"],"is_preprint":false},{"year":2000,"finding":"p107 and pRB have opposing roles in adipocyte differentiation: pRB promotes differentiation and is required for cell cycle exit, while overexpression of p107 antagonizes differentiation; loss of p107 lowers the requirement for PPARgamma without affecting C/EBPalpha-driven transcription.","method":"Knockout fibroblasts, retroviral overexpression, reporter assay, adipogenesis assay","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic loss-of-function plus overexpression, single lab, defined cellular phenotype","pmids":["10995476"],"is_preprint":false},{"year":2002,"finding":"TGFβ signaling induces nuclear translocation of a preformed cytoplasmic complex containing Smad3, E2F4/5, DP1, and p107, which then associates with Smad4 to bind a composite Smad-E2F site on the c-myc promoter for transcriptional repression. p107 acts as a TGFβ signal transducer upstream of CDK in this context.","method":"Co-immunoprecipitation, subcellular fractionation, chromatin immunoprecipitation, reporter assay, cytoplasmic/nuclear complex characterization","journal":"Cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — endogenous Co-IP plus ChIP plus subcellular fractionation plus reporter assay, multiple orthogonal methods in a high-impact study","pmids":["12150994"],"is_preprint":false},{"year":2002,"finding":"Cyclin D1/Cdk4 directly phosphorylates p107 at four specific sites (Thr-369, Ser-640, Ser-964, Ser-975) identified by in vitro kinase assay; these are not efficiently phosphorylated by Cdk2. The RXL motif of p107 facilitates Cdk4-mediated phosphorylation of nonconsensus sites. Nonphosphorylatable p107 at these four sites is not inactivated by cyclin D1/Cdk4 co-expression.","method":"In vitro kinase assay, site-directed mutagenesis, cell cycle arrest reversal assay, phosphopeptide mapping","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro kinase assay with site-directed mutagenesis identifying four specific phosphorylation sites plus in vivo functional validation","pmids":["11884610"],"is_preprint":false},{"year":2002,"finding":"FGF signaling causes rapid dephosphorylation of p107 and p130 (but not pRB) to induce G1 arrest in chondrocytes; p107-/-;p130-/- chondrocytes do not respond to FGF-mediated growth inhibition, while pRB-null chondrocytes respond normally, placing p107 and p130 as critical effectors of FGF growth inhibition.","method":"Genetic epistasis with single and compound knockout mice, chondrocyte micromass culture, metatarsal organ culture, viral oncoprotein rescue assay","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic epistasis with double knockout plus organ culture functional assay, multiple orthogonal approaches","pmids":["12177046"],"is_preprint":false},{"year":2003,"finding":"Oxidative stress (H2O2) induces rapid hypophosphorylation of p107 via PP2A activity: PP2A catalytic subunit physically interacts with p107 in both untreated and H2O2-treated cells; okadaic acid/calyculin A prevent dephosphorylation; SV40 small t (PP2A inhibitor) blocks this response; PP2A-mediated dephosphorylation of p107 contributes to DNA-synthesis inhibition.","method":"Co-immunoprecipitation of PP2A with p107, phosphatase inhibitor treatment, SV40 small t expression, phosphorylation analysis","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — four independent lines of evidence (inhibitors, SV40 small t mutant, Co-IP, activity assay) in one study","pmids":["12621062"],"is_preprint":false},{"year":2004,"finding":"PP2A catalytic subunit specifically interacts with p107 and p130 throughout the cell cycle; PP2A activity, not PP1, is responsible for pocket protein dephosphorylation upon CDK inhibition; the balance between CDK and PP2A activities determines the overall phosphorylation state of p107.","method":"Co-immunoprecipitation of PP2A/C with p107, okadaic acid dose-response, SV40 small t expression, flavopiridol and cycloheximide treatments","journal":"Cell cycle","confidence":"High","confidence_rationale":"Tier 2 / Strong — endogenous Co-IP plus pharmacological and genetic PP2A inhibition, multiple orthogonal methods","pmids":["15467457"],"is_preprint":false},{"year":2004,"finding":"UV irradiation induces rapid dephosphorylation of p107 via a PP2A-like phosphatase, increasing p107/E2F repressor complexes; this is independent of p53 and p21, and occurs with PP2A overexpression in vitro; specific PP2A B subunit overexpression interferes with UV-mediated p107 dephosphorylation.","method":"Phosphatase inhibitor assays, PP2A B-subunit overexpression, in vitro dephosphorylation with PP2A, p53/p21 null fibroblasts","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple pharmacological and genetic approaches, single lab","pmids":["9989818"],"is_preprint":false},{"year":2004,"finding":"Adult p107-null mice have elevated neural stem/progenitor cell numbers in the lateral ventricles with enhanced self-renewal capacity; p107 represses Notch1 expression as shown by chromatin immunoprecipitation and overexpression experiments, placing p107 upstream of Notch1 in neural stem cell regulation.","method":"Neurosphere assay, BrdU labeling, in vivo progenitor ablation/repopulation, chromatin immunoprecipitation, p107 overexpression","journal":"The Journal of cell biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP plus functional neurosphere assay plus in vivo BrdU labeling, single lab","pmids":["15353549"],"is_preprint":false},{"year":2005,"finding":"p107 promotes G1-to-S inhibition by downregulating expression of the F-box protein Skp2, leading to p27 stabilization; ectopic Skp2 restores p27 degradation and S phase entry in p107-overexpressing cells, and Skp2 inactivation abrogates p107's inhibitory effect on S phase.","method":"p107 overexpression and knockout fibroblasts, Skp2 ectopic expression, p27 stability assay, S phase entry (BrdU)","journal":"The Journal of cell biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis rescue (Skp2 restoration) plus p107-/- MEFs, single lab, coherent mechanism","pmids":["15631990"],"is_preprint":false},{"year":2005,"finding":"p107 and p130 (but not pRB) play key roles in transcriptional repression of >20 G2/M genes in response to DNA damage; loss of p107 and p130 partially abrogates repression of PLK1 and other G2/M targets; mice lacking all three RB family proteins fail to accumulate at 4N DNA content after adriamycin treatment.","method":"Gene expression profiling, RB-family knockout MEFs and mouse cells, DNA damage treatment","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic loss-of-function with gene expression readout, single lab","pmids":["15827088"],"is_preprint":false},{"year":2005,"finding":"p107 loss in mice causes replacement of white adipose tissue with brown adipose tissue; WAT from p107-/- mice shows elevated PGC-1alpha and UCP-1; p107-/- precursors display downregulated pRB expression; chromatin IP shows pRB (not p107) binds the PGC-1alpha promoter to repress transcription.","method":"Knockout mouse analysis, ChIP showing pRb at PGC-1alpha promoter, adipocyte differentiation assay, Cre-mediated Rb deletion in primary preadipocytes","journal":"Cell metabolism","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic loss-of-function plus ChIP, single lab; p107 effect appears indirect via pRB regulation of PGC-1alpha","pmids":["16271529"],"is_preprint":false},{"year":2007,"finding":"Mammalian Mip/LIN-9 forms a cell-cycle-phase-specific complex with p107 (or p130) and E2F4 in G0/early G1; this complex is distinct from the Mip/LIN-9–B-Myb complex that forms in late G1/S. CDK4-mediated phosphorylation of p107 disrupts the Mip/LIN-9–p107 interaction. p107 expression blocks B-Myb/Mip/LIN-9-driven cyclin B promoter activation.","method":"Co-immunoprecipitation, cell cycle synchronization, reporter assay, phosphorylated p107 binding analysis","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP across cell cycle phases plus functional reporter, single lab","pmids":["17563750"],"is_preprint":false},{"year":2007,"finding":"p107 represses transcription at the Hes1 promoter; p107-null mice show enhanced Hes1 expression and reduced neuronal commitment; genetic reduction of Hes1 (single allele) in p107-null mice rescues neurosphere numbers and neurogenesis rate, placing p107 upstream of Hes1 in neural progenitor commitment.","method":"Chromatin immunoprecipitation at Hes1 promoter, neurosphere assay, genetic compound mutant, neuronal birthdating","journal":"The Journal of cell biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP plus genetic epistasis (double mutant rescue), single lab","pmids":["17591923"],"is_preprint":false},{"year":2013,"finding":"MAGE-A11 interacts physically with p107 (but not p130), stabilizes p107 by inhibiting its ubiquitination, and links p107 to hypophosphorylated E2F1, activating E2F1 transcriptional activity; in prostate cancer cells with high MAGE-A11, p107 acts as a transcriptional activator rather than repressor.","method":"Co-immunoprecipitation, ubiquitination assay, siRNA knockdown, reporter assay","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP plus ubiquitination assay plus functional reporter, single lab","pmids":["23853093"],"is_preprint":false},{"year":2019,"finding":"In response to p53 activation/DNA damage, p107 cooperates with p130 in the DREAM complex to repress G2/M cell cycle genes (not G1/S genes); pRB and p130 cooperate to repress G1/S genes; p107-DREAM and p130-DREAM repression of G2/M genes reduces mitotic entry.","method":"Gene expression profiling in primary human fibroblasts with RB family knockdowns, p53 activation by DNA damage","journal":"Nucleic acids research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genome-wide expression profiling in defined genetic backgrounds, single lab, clear mechanistic dissection","pmids":["31667499"],"is_preprint":false}],"current_model":"p107 (RBL1) is a nuclear pocket protein that suppresses cell proliferation primarily by binding and repressing the E2F family of transcription factors (especially E2F-4 and E2F-5) and by directly inhibiting cyclin A/cdk2 and cyclin E/cdk2 kinase activity via two independent cyclin-binding domains; its activity is cell-cycle-regulated through sequential phosphorylation by cyclin D1/cdk4 (which dissociates p107 from E2F and releases growth arrest) and dephosphorylation by PP2A (via regulatory subunit PR59); p107 also represses c-Myc transactivation by direct binding, represses RNA Pol III transcription via TFIIIB interaction, participates in a cytoplasmic Smad3/E2F4/p107 complex that translocates to the nucleus to repress c-myc in response to TGFβ, and in the DREAM complex represses G2/M genes following DNA damage, while in neural progenitors it represses Hes1 to promote neuronal commitment and in adipocytes it opposes pRB to restrain brown adipose differentiation."},"narrative":{"mechanistic_narrative":"RBL1 (p107) is a nuclear pocket protein that restrains cell proliferation through dual, mechanistically separable activities: transcriptional repression via E2F factors and direct stoichiometric inhibition of G1/S cyclin-dependent kinases [PMID:1833063, PMID:7743997]. Through an RB-homologous pocket domain that independently binds SV40 large T antigen and adenovirus E1A, p107 assembles cell-cycle-regulated complexes with E2F-4 (and E2F-5) together with cyclin E/cdk2 in G1 and cyclin A/cdk2 in S phase, repressing E2F-dependent transcription and arresting sensitive cells in G1 [PMID:1531040, PMID:1530885, PMID:1532457, PMID:1532458, PMID:1398067, PMID:8319904, PMID:7958925, PMID:7958924, PMID:8657117]. A unique spacer region distinguishes p107 from pRB: it harbors a p21-related cyclin/cdk2-binding domain that, together with an N-terminal site, inhibits cyclin A/cdk2 and cyclin E/cdk2 kinase activity with a Ki comparable to p21 — an inhibitory function pRB lacks [PMID:1532457, PMID:1532458, PMID:7622038, PMID:9199292, PMID:9710622]. p107 activity is governed by phosphorylation: cyclin D1/cdk4 phosphorylates p107 at specific residues (Thr-369, Ser-640, Ser-964, Ser-975) in mid-G1, dissociating it from E2F-4 and releasing the growth block, while a PP2A holoenzyme (including the regulatory subunit PR59 and the C subunit) reverses this phosphorylation in response to oxidative, UV, and FGF stimuli to restore the repressive state [PMID:7797074, PMID:8643455, PMID:9927208, PMID:11884610, PMID:12621062, PMID:15467457]. Beyond E2F, p107 directly binds and represses c-Myc, Sp1, and the TFIIIB subunit of the RNA polymerase III machinery, and acts as a TGFβ signal transducer within a Smad3/E2F4/DP1/p107 complex that translocates to the nucleus to repress c-myc [PMID:8076603, PMID:8146655, PMID:7565695, PMID:10330166, PMID:12150994]. Genetically, p107 functions redundantly with p130 in endochondral bone development and as a tumor suppressor in the retina in a pRB-deficient background, and it controls differentiation programs by repressing Hes1 and Notch1 in neural progenitors and opposing pRB in adipocyte fate [PMID:8682294, PMID:8682293, PMID:9620848, PMID:15353549, PMID:17591923, PMID:16271529].","teleology":[{"year":1991,"claim":"Established that p107 is a distinct RB-family member by defining a pocket domain capable of independently engaging viral oncoproteins, framing it as a candidate growth regulator separate from pRB.","evidence":"cDNA cloning, sequence analysis, and binding assays with SV40 large T antigen and adenovirus E1A","pmids":["1833063"],"confidence":"High","gaps":["Cellular endogenous binding partners not yet identified","Functional consequence of pocket binding unknown at this stage"]},{"year":1992,"claim":"Resolved how p107 connects to the cell cycle by showing it forms temporally distinct E2F complexes — cyclin E/cdk2 in G1 and cyclin A/cdk2 in S phase — distinguishing it from the G1-phase RB–E2F complex.","evidence":"Co-immunoprecipitation, gel mobility shift, and cell cycle fractionation; cyclin E-specific antisera","pmids":["1531040","1530885","1532457","1532458","1398067"],"confidence":"High","gaps":["Identity of the E2F partner not yet established as E2F-4","Functional output of cyclin binding undefined"]},{"year":1992,"claim":"Mapped cyclin A binding to the unique spacer between the pocket A/B sub-segments, revealing a structural feature absent from pRB that enables direct cyclin recruitment.","evidence":"In vitro binding assay with pocket domain mutants","pmids":["1532457","1532458"],"confidence":"High","gaps":["Whether cyclin binding modulates kinase activity not yet tested"]},{"year":1993,"claim":"Demonstrated p107 is a functional E2F repressor and growth suppressor, and that its E1A-independent mutants still inhibit proliferation, establishing mechanistic divergence from pRB.","evidence":"Transient transfection reporter assays, proliferation and flow cytometry assays, Gal4-tethering, monoclonal antibody Co-IP","pmids":["8319904","8458319","8230483","7685208"],"confidence":"High","gaps":["E2F partner identity still inferred as 62-65 kDa phosphoprotein","Cell-type specificity of repression unexplained"]},{"year":1994,"claim":"Identified E2F-4 as the specific p107 partner and c-Myc as a direct non-E2F target, broadening p107's repertoire beyond E2F to a second proliferation-driving transcription factor.","evidence":"Co-IP, reporter and transformation assays, growth rescue experiments","pmids":["7958925","7958924","8076603","8146655"],"confidence":"High","gaps":["Promoter-level mechanism of c-Myc repression not defined","Relative contribution of E2F vs c-Myc repression to arrest unclear"]},{"year":1995,"claim":"Defined two independent growth-suppression domains — an E2F-binding pocket and a p21-related cyclin/cdk2-inhibitory spacer — establishing p107 as a direct CDK inhibitor whose binding is mutually exclusive with p21.","evidence":"In vitro kinase inhibition, competitive binding, deletion mutant growth assays, DNA damage treatment","pmids":["7622038","7743997","7799940","8668177"],"confidence":"High","gaps":["Precise cyclin-binding residues not yet mapped","In vivo significance of CDK inhibition vs E2F repression not resolved"]},{"year":1995,"claim":"Showed that cyclin D1/cdk4 (not cyclin E/cdk2) phosphorylates p107 in mid-G1 to dissociate it from E2F-4 and inactivate its G1 block, establishing the upstream switch controlling p107 activity.","evidence":"In vivo phosphorylation, dominant-negative cdk4, Co-IP, cell synchronization","pmids":["7797074","8643455"],"confidence":"High","gaps":["Specific phosphorylation sites not yet identified","Reversal/dephosphorylation mechanism unknown"]},{"year":1995,"claim":"Extended p107's repressive reach to Sp1 and defined an E2F-dependent autoregulatory loop at its own promoter, showing distinct domains for distinct transcription-factor targets.","evidence":"Endogenous Co-IP, Gal4-Sp1 reporter assays, promoter deletion and site-directed mutagenesis","pmids":["7565695","7791762"],"confidence":"Medium","gaps":["Physiological role of Sp1 repression unclear","Autoregulatory loop tested only in reporter context"]},{"year":1996,"claim":"Provided the in vivo genetic framework: p107 is dispensable alone but redundant with p130 in chondrocyte/bone development and overlapping with pRB, with combined loss causing lethality and dysplasia.","evidence":"Single and compound knockout mice, histology, MEF analysis, E2F partner-switching immunoprecipitation survey","pmids":["8682294","8682293","8657117"],"confidence":"High","gaps":["Molecular basis of functional redundancy with p130 not dissected","Tissue-specific target genes undefined"]},{"year":1997,"claim":"Expanded p107 function to RNA Pol III repression via TFIIIB and rigorously confirmed stoichiometric CDK inhibition through a conserved N-terminal domain, separating it from E2F binding.","evidence":"In vitro reconstitution with purified proteins, pull-down, endogenous complex purification, double-KO MEFs","pmids":["10330166","9199292","8627752","9271376"],"confidence":"High","gaps":["Physiological signals coupling p107 to Pol III regulation unclear"]},{"year":1998,"claim":"Quantified p107 as a dual cyclin/cdk2 inhibitor with two cyclin-binding sites of distinct function, and demonstrated it acts as a tumor suppressor in the retina in a pRB-null background.","evidence":"In vitro Ki determination, domain mutant analysis, peptide competition, chimeric mouse histopathology","pmids":["9710622","9620848","9563849"],"confidence":"High","gaps":["Human retinoblastoma relevance not directly established","Tissue restriction of tumor suppression unexplained"]},{"year":1999,"claim":"Identified PP2A (via the PR59 regulatory subunit) and C/EBPalpha as p107-specific regulators, defining the phosphatase that reactivates p107 and a differentiation-linked complex disruptor.","evidence":"Yeast two-hybrid, Co-IP, dephosphorylation and cell cycle assays, EMSA disruption with purified C/EBPalpha","pmids":["9927208","10082561"],"confidence":"High","gaps":["PP2A targeting specificity to p107 vs p130 not fully defined","In vivo role of PR59 untested"]},{"year":2002,"claim":"Mapped the four cyclin D1/cdk4 phosphorylation sites and revealed a TGFβ signal-transduction role, positioning p107 within a cytoplasmic Smad3/E2F4/DP1 complex that represses c-myc upon nuclear translocation.","evidence":"In vitro kinase assay with site-directed mutagenesis, phosphopeptide mapping, Co-IP, fractionation, ChIP, reporter assays","pmids":["11884610","12150994"],"confidence":"High","gaps":["Coordination between CDK phosphorylation and TGFβ complex assembly unresolved","Generality of Smad-E2F site beyond c-myc unclear"]},{"year":2003,"claim":"Established stress-responsive PP2A-mediated p107 dephosphorylation as a route to growth arrest, with PP2A physically bound to p107 and activated by oxidative and UV stress.","evidence":"Co-IP, phosphatase inhibitor and SV40 small t experiments, in vitro dephosphorylation, p53/p21-null fibroblasts","pmids":["12621062","9989818","15467457"],"confidence":"High","gaps":["Specific PP2A regulatory subunit for stress responses not pinned down","Signal relay from stress sensor to PP2A unknown"]},{"year":2004,"claim":"Placed p107 (with p130) as a critical effector of FGF growth inhibition in chondrocytes and as a repressor of Notch1 controlling neural stem cell self-renewal, linking it to differentiation-stage decisions.","evidence":"Compound knockout mice, chondrocyte/metatarsal organ culture, neurosphere assays, BrdU labeling, ChIP","pmids":["12177046","15353549"],"confidence":"Medium","gaps":["Direct chondrocyte target genes of p107 undefined","Mechanism coupling FGF to p107 dephosphorylation not detailed"]},{"year":2005,"claim":"Connected p107 to the SCF-Skp2/p27 axis and to G2/M gene repression after DNA damage, and revealed it opposes pRB in adipocyte fate by indirect regulation of PGC-1alpha.","evidence":"Knockout and overexpression fibroblasts, Skp2 rescue, p27 stability and BrdU assays, gene expression profiling, ChIP on PGC-1alpha promoter","pmids":["15631990","15827088","16271529"],"confidence":"Medium","gaps":["Whether p107 directly regulates Skp2 transcription unclear","p107 effect on adipose appears indirect via pRB"]},{"year":2007,"claim":"Defined p107 as a subunit of cell-cycle-phase-specific LIN-9/MuvB-containing complexes with E2F4 and as a repressor at Hes1, mechanistically linking it to G2/M gene control and neuronal commitment.","evidence":"Co-IP across cell cycle, reporter assays, ChIP at Hes1, genetic compound mutant rescue, neuronal birthdating","pmids":["17563750","17591923"],"confidence":"Medium","gaps":["Full composition of the p107-MuvB complex not enumerated","Direct vs indirect Hes1 regulation in vivo not fully separated"]},{"year":2013,"claim":"Revealed a context-dependent reversal of p107 function: MAGE-A11 stabilizes p107 and converts it into a transcriptional co-activator of E2F1 in prostate cancer cells.","evidence":"Co-IP, ubiquitination assay, siRNA knockdown, reporter assays","pmids":["23853093"],"confidence":"Medium","gaps":["Single lab; structural basis of the activator switch unknown","Physiological prevalence of this mode beyond high-MAGE-A11 tumors unclear"]},{"year":2019,"claim":"Refined the DREAM-complex model showing p107 cooperates with p130 to specifically repress G2/M genes after p53 activation, distinct from pRB/p130 repression of G1/S genes.","evidence":"Genome-wide expression profiling in primary human fibroblasts with RB-family knockdowns and DNA damage","pmids":["31667499"],"confidence":"Medium","gaps":["Direct DREAM subunit interactions of p107 not biochemically resolved here","Determinants of G2/M vs G1/S target selectivity unknown"]},{"year":null,"claim":"How the multiple regulatory inputs (CDK phosphorylation, PP2A dephosphorylation, MAGE-A11 stabilization, TGFβ/FGF signaling) are integrated to switch p107 between repressor and activator states across tissues remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unified structural model of phospho-regulated p107 states","Tissue-specific target gene maps incomplete","Human disease relevance beyond mouse retinoblastoma underexplored"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140110","term_label":"transcription regulator activity","supporting_discovery_ids":[4,7,9,10,16,22,32]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[11,23,27]},{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[11,23,27]},{"term_id":"GO:0060089","term_label":"molecular transducer activity","supporting_discovery_ids":[32,34]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[1,4,32]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[32]}],"pathway":[{"term_id":"R-HSA-1640170","term_label":"Cell Cycle","supporting_discovery_ids":[1,3,4,11,13,40,45]},{"term_id":"R-HSA-74160","term_label":"Gene expression (Transcription)","supporting_discovery_ids":[4,10,16,22,32]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[32,34]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[19,26,38,43,41]}],"complexes":["p107–E2F4–cyclin/cdk2 complex","DREAM complex","LIN-9/MuvB complex","Smad3–E2F4/5–DP1–p107 complex"],"partners":["E2F4","CCNA2","CCNE1","CDK2","MYC","SP1","CCND1","PPP2CA"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P28749","full_name":"Retinoblastoma-like protein 1","aliases":["107 kDa retinoblastoma-associated protein","p107","pRb1"],"length_aa":1068,"mass_kda":120.8,"function":"Key regulator of entry into cell division (PubMed:17671431). Directly involved in heterochromatin formation by maintaining overall chromatin structure and, in particular, that of constitutive heterochromatin by stabilizing histone methylation (By similarity). Recruits and targets histone methyltransferases KMT5B and KMT5C, leading to epigenetic transcriptional repression (By similarity). Controls histone H4 'Lys-20' trimethylation (By similarity). Probably acts as a transcription repressor by recruiting chromatin-modifying enzymes to promoters (By similarity). Potent inhibitor of E2F-mediated trans-activation (PubMed:8319904). May act as a tumor suppressor (PubMed:8319904)","subcellular_location":"Nucleus","url":"https://www.uniprot.org/uniprotkb/P28749/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/RBL1","classification":"Not Classified","n_dependent_lines":2,"n_total_lines":1208,"dependency_fraction":0.0016556291390728477},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"CDK2","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/RBL1","total_profiled":1310},"omim":[{"mim_id":"621288","title":"LIN52 DREAM MUVB CORE COMPLEX COMPONENT; LIN52","url":"https://www.omim.org/entry/621288"},{"mim_id":"621287","title":"LIN37 DREAM MUVB CORE COMPLEX COMPONENT; LIN37","url":"https://www.omim.org/entry/621287"},{"mim_id":"618055","title":"CELLULAR REPRESSOR OF E1A-STIMULATED GENES 1; CREG1","url":"https://www.omim.org/entry/618055"},{"mim_id":"617108","title":"SESSILE SERRATED POLYPOSIS CANCER SYNDROME; SSPCS","url":"https://www.omim.org/entry/617108"},{"mim_id":"616714","title":"HMG-BOX TRANSCRIPTION FACTOR 1; HBP1","url":"https://www.omim.org/entry/616714"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Enhanced","locations":[{"location":"Nucleoplasm","reliability":"Enhanced"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"bone marrow","ntpm":13.7}],"url":"https://www.proteinatlas.org/search/RBL1"},"hgnc":{"alias_symbol":["p107","cp107","PRB1"],"prev_symbol":[]},"alphafold":{"accession":"P28749","domains":[{"cath_id":"1.10.472.10","chopping":"2-115","consensus_level":"medium","plddt":81.915,"start":2,"end":115},{"cath_id":"1.10.472.10","chopping":"387-565","consensus_level":"high","plddt":90.6013,"start":387,"end":565},{"cath_id":"1.10.472.10","chopping":"567-598_782-891_924-972","consensus_level":"medium","plddt":88.6232,"start":567,"end":972},{"cath_id":"1.10.472","chopping":"118-153_168-319","consensus_level":"medium","plddt":90.4585,"start":118,"end":319}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P28749","model_url":"https://alphafold.ebi.ac.uk/files/AF-P28749-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P28749-F1-predicted_aligned_error_v6.png","plddt_mean":71.75},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=RBL1","jax_strain_url":"https://www.jax.org/strain/search?query=RBL1"},"sequence":{"accession":"P28749","fasta_url":"https://rest.uniprot.org/uniprotkb/P28749.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P28749/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P28749"}},"corpus_meta":[{"pmid":"1531040","id":"PMC_1531040","title":"The 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The unique spacer sequence between the A and B sub-segments of the p107 pocket distinguishes it from RB.\",\n      \"method\": \"cDNA cloning, sequence analysis, binding assays with T antigen and E1A\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct biochemical binding assays combined with sequence/domain analysis, foundational paper replicated by multiple subsequent studies\",\n      \"pmids\": [\"1833063\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1992,\n      \"finding\": \"p107 forms a cell cycle-regulated complex with E2F and cyclin A during S phase, distinct from the G1-phase RB–E2F complex. This S-phase complex also contains p33cdk2.\",\n      \"method\": \"Co-immunoprecipitation, gel mobility shift assay, cell cycle fractionation\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP across multiple labs in the same year (PMID 1531040, 1530885, 1532457, 1532458), independently replicated\",\n      \"pmids\": [\"1531040\", \"1530885\", \"1532457\", \"1532458\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1992,\n      \"finding\": \"Cyclin A binds directly to the p107 pocket domain (specifically the unique spacer sequence between the A and B sub-segments) in the absence of viral oncoproteins; this interaction does not occur with the RB pocket.\",\n      \"method\": \"In vitro binding assay, domain mapping with pocket mutants\",\n      \"journal\": \"Science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct in vitro binding assay with domain mutants, replicated by independent laboratory (PMID 1532458)\",\n      \"pmids\": [\"1532457\", \"1532458\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1992,\n      \"finding\": \"Cyclin E and its associated cdk2 form a complex with E2F and p107 specifically during G1, whereas the cyclin A/cdk2/p107/E2F complex is S-phase specific, demonstrating temporally distinct cyclin partnerships for p107.\",\n      \"method\": \"Immunoprecipitation with cyclin E-specific antisera, cell cycle synchronization\",\n      \"journal\": \"Genes & development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — specific antisera immunoprecipitation across cell cycle phases, replicated in subsequent studies\",\n      \"pmids\": [\"1398067\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1993,\n      \"finding\": \"p107 is a potent inhibitor of E2F-mediated transactivation; overexpression of p107 arrests sensitive cells in G1. Growth arrest by p107 and pRB is rescued differentially by cell cycle regulators, and certain p107 mutants unable to associate with E1A still inhibit proliferation, indicating mechanistic differences from pRB.\",\n      \"method\": \"Transient transfection, reporter assay, cell proliferation assay, flow cytometry\",\n      \"journal\": \"Genes & development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal functional assays (transcription, proliferation, cell cycle), independently confirmed by other groups\",\n      \"pmids\": [\"8319904\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1993,\n      \"finding\": \"p107 inhibits E2F-dependent transcription in a co-transfection assay, and this repression correlates with the appearance of p107-containing E2F complexes at the G1/S transition rather than earlier in G1 like RB.\",\n      \"method\": \"Co-transfection reporter assay, EMSA, co-immunoprecipitation\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reporter assay plus EMSA plus Co-IP in same study, replicated across labs\",\n      \"pmids\": [\"8458319\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1993,\n      \"finding\": \"p107 associates in vivo with cyclin A, cyclin E, cdk2, and a 62–65 kDa E2F-like phosphoprotein (subsequently identified as E2F-4) that is immunologically distinct from pRB-associated E2F-1.\",\n      \"method\": \"Monoclonal antibody immunoprecipitation, biochemical characterization\",\n      \"journal\": \"Journal of virology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — panel of monoclonal antibodies, multiple Co-IPs, replicated by parallel studies\",\n      \"pmids\": [\"8230483\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1993,\n      \"finding\": \"p107 functions as a general transcriptional repressor when tethered to a promoter via E2F, and this repression is overcome by adenovirus E1A. Repression is cell-type-specific (absent in F9 embryonal carcinoma cells, present in differentiated derivatives).\",\n      \"method\": \"Transient co-transfection reporter assay, Gal4 fusion constructs\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reporter assay with Gal4-tethering approach, single lab, two methods\",\n      \"pmids\": [\"7685208\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1993,\n      \"finding\": \"HPV16 E7 binds p107 in vivo through sequences overlapping but not identical to the RB-binding region, and this interaction is associated with a histone H1 kinase activity restricted to G2/M phase.\",\n      \"method\": \"Co-immunoprecipitation, kinase assay, E7 point mutant analysis\",\n      \"journal\": \"Journal of virology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus kinase assay plus mutant analysis, single lab\",\n      \"pmids\": [\"8386265\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"E2F-4 is a specific binding partner of p107 in vivo; p107 binding regulates E2F-4 transcriptional activity and suppresses the ability of E2F-4 to transform immortalized rodent cells.\",\n      \"method\": \"Co-immunoprecipitation, reporter assay, transformation assay\",\n      \"journal\": \"Genes & development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — two independent labs simultaneously demonstrated E2F-4/p107 association (PMID 7958925, 7958924) using Co-IP and functional assays\",\n      \"pmids\": [\"7958925\", \"7958924\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"p107 binds directly to the N-terminal transactivation domain of c-Myc in vivo and suppresses c-Myc-mediated transactivation; expression of c-Myc releases cells from p107-induced growth arrest but not pRB-induced arrest.\",\n      \"method\": \"Co-immunoprecipitation, reporter transactivation assay, cell growth rescue experiment\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo Co-IP confirmed independently (PMID 8146655 used cDNA library screen + in vivo association), two orthogonal functional assays\",\n      \"pmids\": [\"8076603\", \"8146655\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"p107 contains a p21CIP1-related cyclin/cdk2-binding domain (spacer region) that inhibits phosphorylation of target substrates by cyclin A/cdk2 and cyclin E/cdk2; binding of p107 and p21 to cyclin/cdk2 is mutually exclusive. DNA damage-elevated p21 displaces p107 from cyclin/cdk2 complexes. Activation of p107-bound cyclin/cdk kinases leads to dissociation of p107 from E2F.\",\n      \"method\": \"In vitro kinase inhibition assay, competitive binding, co-immunoprecipitation, DNA damage treatment\",\n      \"journal\": \"Genes & development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstituted kinase assay plus mutually exclusive binding experiments plus cellular validation, multiple orthogonal methods\",\n      \"pmids\": [\"7622038\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"p107 contains two independent growth suppression domains: one mediating E2F interaction and one mediating cyclin A/E-cdk2 interaction. In C33A cells, only the cyclin-binding domain is active as a growth suppressor, revealing a functional difference from pRB.\",\n      \"method\": \"Structure-function analysis with deletion mutants, co-expression growth assay\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — systematic domain-deletion analysis with functional readouts in multiple cell lines, comprehensive structure-function study\",\n      \"pmids\": [\"7743997\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"Cyclin D1/cdk4, but not cyclin E/cdk2, phosphorylates p107 in vivo beginning ~8 hours after serum stimulation; phosphorylation by cyclin D1/cdk4 causes loss of p107 association with E2F-4 and release of the p107-induced cell cycle block.\",\n      \"method\": \"In vivo phosphorylation assay, dominant-negative cdk4 expression, co-immunoprecipitation, cell cycle analysis\",\n      \"journal\": \"Genes & development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — dominant-negative approach plus biochemical phosphorylation analysis plus Co-IP, multiple orthogonal methods, independently confirmed\",\n      \"pmids\": [\"7797074\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"p107 phosphorylation begins in mid-G1 via cyclin D-associated kinase activity; hypophosphorylated p107 selectively binds E2F-4, and G1 cyclin-dependent phosphorylation of p107 dissociates p107–E2F-4 complexes and inactivates p107's G1 blocking function.\",\n      \"method\": \"Cell synchronization, phosphorylation timing analysis, co-immunoprecipitation, cell cycle block assay\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — synchronized cell biochemistry plus functional G1 block assay, consistent with parallel Beijersbergen et al. findings\",\n      \"pmids\": [\"8643455\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"p107's ability to suppress E2F-dependent transcription requires E2F binding but does not require association with cyclin A/cdk2; both E2F-dependent and E2F-independent events correlate with p107-mediated growth suppression.\",\n      \"method\": \"p107 mutant analysis, reporter assay, growth suppression assay\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mutant analysis with functional readouts, single lab, two orthogonal assays\",\n      \"pmids\": [\"7799940\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"p107 associates with transcription factor Sp1 in vivo and represses Sp1-dependent transcription; this repression is mediated through a region of p107 distinct from the pocket domain required for E2F regulation.\",\n      \"method\": \"Co-immunoprecipitation from multiple cell lines, reporter assay with Gal4-Sp1 chimera, domain mapping\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — endogenous Co-IP plus domain-specific reporter assay, single lab\",\n      \"pmids\": [\"7565695\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"The p107 promoter contains tandem E2F binding sites; the retinoblastoma protein and p107 itself repress p107 promoter activity through the 5' (distal) E2F site, while the 3' (proximal, initiation-site) copy is more important for basal activity. This defines an autoregulatory loop.\",\n      \"method\": \"Promoter deletion analysis, site-directed mutagenesis, reporter assay, co-transfection\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mutagenesis of specific E2F sites with reporter assay, single lab\",\n      \"pmids\": [\"7791762\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"E2F-4 switches from p130 (in G0/quiescence) to association with p107 and pRB as cells re-enter the cell cycle at the G1-to-S transition; E2F-1, -2, and -3 bind only pRB and are restricted to post-G1/S; E2F-4 accounts for the vast majority of endogenous E2F activity.\",\n      \"method\": \"Immunoprecipitation with specific antisera, EMSA, cell synchronization\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — systematic immunoprecipitation survey across cell cycle phases with specific antisera for each E2F/DP and pocket protein\",\n      \"pmids\": [\"8657117\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"p107 and p130 have redundant roles in limb development: simultaneous genetic inactivation of both p107 and p130 causes deregulated chondrocyte growth, defective endochondral bone development, and neonatal lethality, while single knockouts are largely normal.\",\n      \"method\": \"Gene targeting in mouse, histological analysis, MEF culture analysis\",\n      \"journal\": \"Genes & development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic epistasis via double knockout mouse, multiple tissues analyzed, phenotype replicated in independent knockout studies\",\n      \"pmids\": [\"8682294\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"Targeted disruption of mouse p107 alone produces viable, fertile mice with no obvious abnormalities; combined Rb+/-;p107-/- mice show growth retardation and retinal dysplasia; Rb-/-;p107-/- embryos die ~2 days earlier than Rb-/- embryos with accelerated apoptosis in liver and CNS, demonstrating overlapping functions of p107 and Rb in vivo.\",\n      \"method\": \"Homologous recombination gene targeting, compound mutant generation, histological analysis\",\n      \"journal\": \"Genes & development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic epistasis via compound knockout mice, multiple phenotypic readouts, independently replicated (PMID 8682294)\",\n      \"pmids\": [\"8682293\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"p107 pocket domain is sufficient for E2F inactivation, general transcriptional repressor activity, and most growth suppressor activity; the A and B sub-domains of the pocket are fully functional even when expressed as separate proteins, suggesting they interact at the promoter.\",\n      \"method\": \"Deletion mutagenesis, Gal4-fusion reporter assay, co-expression growth assay\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — systematic domain deletions with two functional readouts, single lab\",\n      \"pmids\": [\"8668177\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"p107 and p130 repress RNA polymerase III transcription by directly interacting with the TFIIIB subunit of the Pol III transcription machinery; disruption by HPV E7 or genetic loss of p107/p130 deregulates Pol III activity.\",\n      \"method\": \"Transient transfection assay, pull-down with recombinant proteins, co-immunoprecipitation, cofractionation, MEFs from double-knockout mice\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct pull-down plus endogenous Co-IP plus genetic validation with double-KO fibroblasts, multiple orthogonal methods\",\n      \"pmids\": [\"10330166\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"p107 and p130 use a conserved N-terminal domain (distinct from the E2F-binding pocket) to stoichiometrically inhibit cyclin A-cdk2 and cyclin E-cdk2 kinase activity in vitro; endogenous p130–cyclin A–cdk2 complexes purified from human cells display low kinase activity that is augmented upon dissociation of p130.\",\n      \"method\": \"In vitro reconstitution with purified recombinant proteins, kinase assay, purification of endogenous complexes\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution with purified components plus endogenous complex purification, mechanistically rigorous\",\n      \"pmids\": [\"9199292\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"SV40 large T antigen alters the phosphorylation state of p107 and p130, requiring both the LXCXE domain (for binding) and the N-terminal J domain homology region; the J domain effect is separable from mere binding.\",\n      \"method\": \"Transient expression assay, phosphorylation state analysis, T antigen domain mutants\",\n      \"journal\": \"Journal of virology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — domain mutant analysis with phosphorylation readout, single lab\",\n      \"pmids\": [\"8627752\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"The J domain of SV40 large T antigen is required to inactivate p130 and p107; a heterologous DnaJ protein J domain functionally substitutes for T antigen's N terminus in altering p107/p130 phosphorylation; J domain is dispensable in MEFs lacking both p130 and p107, placing p107/p130 as the relevant J domain targets.\",\n      \"method\": \"Domain mutant and heterologous J domain substitution, phosphorylation analysis, MEFs from p107/p130 double-KO\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic epistasis with double-KO MEFs plus heterologous J domain rescue, multiple orthogonal methods\",\n      \"pmids\": [\"9271376\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"p107 loss in a pRB-deficient background (p107/pRB double-null chimeric mice) leads to retinoblastoma, providing first in vivo evidence that p107 exerts a tumor suppressor function in the retina, suppressing retinoblastoma development caused by pRB deficiency.\",\n      \"method\": \"Gene targeting, chimeric mouse generation, histopathology\",\n      \"journal\": \"Genes & development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct genetic epistasis with tumor phenotype, independently supported by Lee et al. 1996\",\n      \"pmids\": [\"9620848\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"p107 is a dual cyclin/cdk2 inhibitor with a Ki comparable to p21/WAF1; p107 harbors two cyclin-binding sites (N-terminal and C-terminal/spacer), both required for kinase inhibition. The C-terminal site is a substrate but not an inhibitor; the N-terminal site inhibits without being an efficient substrate. pRB does not inhibit cdks.\",\n      \"method\": \"In vitro kinase inhibition assay with Ki determination, domain mutant analysis, peptide competition\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — rigorous in vitro reconstitution with Ki determination plus systematic domain mutant analysis, mechanistically detailed\",\n      \"pmids\": [\"9710622\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"p107 expression is transcriptionally regulated in a growth-state-dependent manner via E2F-mediated repression in quiescent cells; p130 controls p107 expression in quiescent cells, whereas p130 protein stability is posttranscriptionally controlled by proteasomal degradation upon CDK-mediated phosphorylation.\",\n      \"method\": \"Northern blot, promoter analysis, proteasome inhibitor treatment, Western blot across growth states\",\n      \"journal\": \"Cell growth & differentiation\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple methods (transcriptional vs. posttranslational) but single lab\",\n      \"pmids\": [\"9563849\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"A novel PP2A regulatory subunit PR59 specifically co-immunoprecipitates with p107 (but not pRB) and promotes dephosphorylation of p107 (but not pRB) when overexpressed, causing G1 accumulation; PR59 is a genuine PP2A component that targets the catalytic subunit specifically to p107.\",\n      \"method\": \"Yeast two-hybrid (isolation), co-immunoprecipitation, dephosphorylation assay, cell cycle analysis\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — Co-IP plus functional dephosphorylation assay plus cell cycle readout, multiple orthogonal methods\",\n      \"pmids\": [\"9927208\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"C/EBPalpha directly interacts with p107 (co-immunoprecipitation) and disrupts S-phase-specific E2F-p107 complexes through a protein-protein interaction mediated by a short C/EBPalpha domain with E2F homology, independent of C/EBPalpha DNA binding.\",\n      \"method\": \"Co-immunoprecipitation, EMSA, bacterially expressed purified C/EBPalpha disruption assay\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — endogenous Co-IP plus in vitro disruption assay with purified protein, multiple orthogonal methods\",\n      \"pmids\": [\"10082561\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"p107 and pRB have opposing roles in adipocyte differentiation: pRB promotes differentiation and is required for cell cycle exit, while overexpression of p107 antagonizes differentiation; loss of p107 lowers the requirement for PPARgamma without affecting C/EBPalpha-driven transcription.\",\n      \"method\": \"Knockout fibroblasts, retroviral overexpression, reporter assay, adipogenesis assay\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic loss-of-function plus overexpression, single lab, defined cellular phenotype\",\n      \"pmids\": [\"10995476\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"TGFβ signaling induces nuclear translocation of a preformed cytoplasmic complex containing Smad3, E2F4/5, DP1, and p107, which then associates with Smad4 to bind a composite Smad-E2F site on the c-myc promoter for transcriptional repression. p107 acts as a TGFβ signal transducer upstream of CDK in this context.\",\n      \"method\": \"Co-immunoprecipitation, subcellular fractionation, chromatin immunoprecipitation, reporter assay, cytoplasmic/nuclear complex characterization\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — endogenous Co-IP plus ChIP plus subcellular fractionation plus reporter assay, multiple orthogonal methods in a high-impact study\",\n      \"pmids\": [\"12150994\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"Cyclin D1/Cdk4 directly phosphorylates p107 at four specific sites (Thr-369, Ser-640, Ser-964, Ser-975) identified by in vitro kinase assay; these are not efficiently phosphorylated by Cdk2. The RXL motif of p107 facilitates Cdk4-mediated phosphorylation of nonconsensus sites. Nonphosphorylatable p107 at these four sites is not inactivated by cyclin D1/Cdk4 co-expression.\",\n      \"method\": \"In vitro kinase assay, site-directed mutagenesis, cell cycle arrest reversal assay, phosphopeptide mapping\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro kinase assay with site-directed mutagenesis identifying four specific phosphorylation sites plus in vivo functional validation\",\n      \"pmids\": [\"11884610\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"FGF signaling causes rapid dephosphorylation of p107 and p130 (but not pRB) to induce G1 arrest in chondrocytes; p107-/-;p130-/- chondrocytes do not respond to FGF-mediated growth inhibition, while pRB-null chondrocytes respond normally, placing p107 and p130 as critical effectors of FGF growth inhibition.\",\n      \"method\": \"Genetic epistasis with single and compound knockout mice, chondrocyte micromass culture, metatarsal organ culture, viral oncoprotein rescue assay\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic epistasis with double knockout plus organ culture functional assay, multiple orthogonal approaches\",\n      \"pmids\": [\"12177046\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Oxidative stress (H2O2) induces rapid hypophosphorylation of p107 via PP2A activity: PP2A catalytic subunit physically interacts with p107 in both untreated and H2O2-treated cells; okadaic acid/calyculin A prevent dephosphorylation; SV40 small t (PP2A inhibitor) blocks this response; PP2A-mediated dephosphorylation of p107 contributes to DNA-synthesis inhibition.\",\n      \"method\": \"Co-immunoprecipitation of PP2A with p107, phosphatase inhibitor treatment, SV40 small t expression, phosphorylation analysis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — four independent lines of evidence (inhibitors, SV40 small t mutant, Co-IP, activity assay) in one study\",\n      \"pmids\": [\"12621062\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"PP2A catalytic subunit specifically interacts with p107 and p130 throughout the cell cycle; PP2A activity, not PP1, is responsible for pocket protein dephosphorylation upon CDK inhibition; the balance between CDK and PP2A activities determines the overall phosphorylation state of p107.\",\n      \"method\": \"Co-immunoprecipitation of PP2A/C with p107, okadaic acid dose-response, SV40 small t expression, flavopiridol and cycloheximide treatments\",\n      \"journal\": \"Cell cycle\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — endogenous Co-IP plus pharmacological and genetic PP2A inhibition, multiple orthogonal methods\",\n      \"pmids\": [\"15467457\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"UV irradiation induces rapid dephosphorylation of p107 via a PP2A-like phosphatase, increasing p107/E2F repressor complexes; this is independent of p53 and p21, and occurs with PP2A overexpression in vitro; specific PP2A B subunit overexpression interferes with UV-mediated p107 dephosphorylation.\",\n      \"method\": \"Phosphatase inhibitor assays, PP2A B-subunit overexpression, in vitro dephosphorylation with PP2A, p53/p21 null fibroblasts\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple pharmacological and genetic approaches, single lab\",\n      \"pmids\": [\"9989818\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Adult p107-null mice have elevated neural stem/progenitor cell numbers in the lateral ventricles with enhanced self-renewal capacity; p107 represses Notch1 expression as shown by chromatin immunoprecipitation and overexpression experiments, placing p107 upstream of Notch1 in neural stem cell regulation.\",\n      \"method\": \"Neurosphere assay, BrdU labeling, in vivo progenitor ablation/repopulation, chromatin immunoprecipitation, p107 overexpression\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP plus functional neurosphere assay plus in vivo BrdU labeling, single lab\",\n      \"pmids\": [\"15353549\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"p107 promotes G1-to-S inhibition by downregulating expression of the F-box protein Skp2, leading to p27 stabilization; ectopic Skp2 restores p27 degradation and S phase entry in p107-overexpressing cells, and Skp2 inactivation abrogates p107's inhibitory effect on S phase.\",\n      \"method\": \"p107 overexpression and knockout fibroblasts, Skp2 ectopic expression, p27 stability assay, S phase entry (BrdU)\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis rescue (Skp2 restoration) plus p107-/- MEFs, single lab, coherent mechanism\",\n      \"pmids\": [\"15631990\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"p107 and p130 (but not pRB) play key roles in transcriptional repression of >20 G2/M genes in response to DNA damage; loss of p107 and p130 partially abrogates repression of PLK1 and other G2/M targets; mice lacking all three RB family proteins fail to accumulate at 4N DNA content after adriamycin treatment.\",\n      \"method\": \"Gene expression profiling, RB-family knockout MEFs and mouse cells, DNA damage treatment\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic loss-of-function with gene expression readout, single lab\",\n      \"pmids\": [\"15827088\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"p107 loss in mice causes replacement of white adipose tissue with brown adipose tissue; WAT from p107-/- mice shows elevated PGC-1alpha and UCP-1; p107-/- precursors display downregulated pRB expression; chromatin IP shows pRB (not p107) binds the PGC-1alpha promoter to repress transcription.\",\n      \"method\": \"Knockout mouse analysis, ChIP showing pRb at PGC-1alpha promoter, adipocyte differentiation assay, Cre-mediated Rb deletion in primary preadipocytes\",\n      \"journal\": \"Cell metabolism\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic loss-of-function plus ChIP, single lab; p107 effect appears indirect via pRB regulation of PGC-1alpha\",\n      \"pmids\": [\"16271529\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Mammalian Mip/LIN-9 forms a cell-cycle-phase-specific complex with p107 (or p130) and E2F4 in G0/early G1; this complex is distinct from the Mip/LIN-9–B-Myb complex that forms in late G1/S. CDK4-mediated phosphorylation of p107 disrupts the Mip/LIN-9–p107 interaction. p107 expression blocks B-Myb/Mip/LIN-9-driven cyclin B promoter activation.\",\n      \"method\": \"Co-immunoprecipitation, cell cycle synchronization, reporter assay, phosphorylated p107 binding analysis\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP across cell cycle phases plus functional reporter, single lab\",\n      \"pmids\": [\"17563750\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"p107 represses transcription at the Hes1 promoter; p107-null mice show enhanced Hes1 expression and reduced neuronal commitment; genetic reduction of Hes1 (single allele) in p107-null mice rescues neurosphere numbers and neurogenesis rate, placing p107 upstream of Hes1 in neural progenitor commitment.\",\n      \"method\": \"Chromatin immunoprecipitation at Hes1 promoter, neurosphere assay, genetic compound mutant, neuronal birthdating\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP plus genetic epistasis (double mutant rescue), single lab\",\n      \"pmids\": [\"17591923\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"MAGE-A11 interacts physically with p107 (but not p130), stabilizes p107 by inhibiting its ubiquitination, and links p107 to hypophosphorylated E2F1, activating E2F1 transcriptional activity; in prostate cancer cells with high MAGE-A11, p107 acts as a transcriptional activator rather than repressor.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, siRNA knockdown, reporter assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus ubiquitination assay plus functional reporter, single lab\",\n      \"pmids\": [\"23853093\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"In response to p53 activation/DNA damage, p107 cooperates with p130 in the DREAM complex to repress G2/M cell cycle genes (not G1/S genes); pRB and p130 cooperate to repress G1/S genes; p107-DREAM and p130-DREAM repression of G2/M genes reduces mitotic entry.\",\n      \"method\": \"Gene expression profiling in primary human fibroblasts with RB family knockdowns, p53 activation by DNA damage\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genome-wide expression profiling in defined genetic backgrounds, single lab, clear mechanistic dissection\",\n      \"pmids\": [\"31667499\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"p107 (RBL1) is a nuclear pocket protein that suppresses cell proliferation primarily by binding and repressing the E2F family of transcription factors (especially E2F-4 and E2F-5) and by directly inhibiting cyclin A/cdk2 and cyclin E/cdk2 kinase activity via two independent cyclin-binding domains; its activity is cell-cycle-regulated through sequential phosphorylation by cyclin D1/cdk4 (which dissociates p107 from E2F and releases growth arrest) and dephosphorylation by PP2A (via regulatory subunit PR59); p107 also represses c-Myc transactivation by direct binding, represses RNA Pol III transcription via TFIIIB interaction, participates in a cytoplasmic Smad3/E2F4/p107 complex that translocates to the nucleus to repress c-myc in response to TGFβ, and in the DREAM complex represses G2/M genes following DNA damage, while in neural progenitors it represses Hes1 to promote neuronal commitment and in adipocytes it opposes pRB to restrain brown adipose differentiation.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"RBL1 (p107) is a nuclear pocket protein that restrains cell proliferation through dual, mechanistically separable activities: transcriptional repression via E2F factors and direct stoichiometric inhibition of G1/S cyclin-dependent kinases [#0, #12]. Through an RB-homologous pocket domain that independently binds SV40 large T antigen and adenovirus E1A, p107 assembles cell-cycle-regulated complexes with E2F-4 (and E2F-5) together with cyclin E/cdk2 in G1 and cyclin A/cdk2 in S phase, repressing E2F-dependent transcription and arresting sensitive cells in G1 [#1, #3, #4, #9, #18]. A unique spacer region distinguishes p107 from pRB: it harbors a p21-related cyclin/cdk2-binding domain that, together with an N-terminal site, inhibits cyclin A/cdk2 and cyclin E/cdk2 kinase activity with a Ki comparable to p21 — an inhibitory function pRB lacks [#2, #11, #23, #27]. p107 activity is governed by phosphorylation: cyclin D1/cdk4 phosphorylates p107 at specific residues (Thr-369, Ser-640, Ser-964, Ser-975) in mid-G1, dissociating it from E2F-4 and releasing the growth block, while a PP2A holoenzyme (including the regulatory subunit PR59 and the C subunit) reverses this phosphorylation in response to oxidative, UV, and FGF stimuli to restore the repressive state [#13, #14, #29, #33, #35, #36]. Beyond E2F, p107 directly binds and represses c-Myc, Sp1, and the TFIIIB subunit of the RNA polymerase III machinery, and acts as a TGFβ signal transducer within a Smad3/E2F4/DP1/p107 complex that translocates to the nucleus to repress c-myc [#10, #16, #22, #32]. Genetically, p107 functions redundantly with p130 in endochondral bone development and as a tumor suppressor in the retina in a pRB-deficient background, and it controls differentiation programs by repressing Hes1 and Notch1 in neural progenitors and opposing pRB in adipocyte fate [#19, #20, #26, #38, #43, #41].\",\n  \"teleology\": [\n    {\n      \"year\": 1991,\n      \"claim\": \"Established that p107 is a distinct RB-family member by defining a pocket domain capable of independently engaging viral oncoproteins, framing it as a candidate growth regulator separate from pRB.\",\n      \"evidence\": \"cDNA cloning, sequence analysis, and binding assays with SV40 large T antigen and adenovirus E1A\",\n      \"pmids\": [\"1833063\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Cellular endogenous binding partners not yet identified\", \"Functional consequence of pocket binding unknown at this stage\"]\n    },\n    {\n      \"year\": 1992,\n      \"claim\": \"Resolved how p107 connects to the cell cycle by showing it forms temporally distinct E2F complexes — cyclin E/cdk2 in G1 and cyclin A/cdk2 in S phase — distinguishing it from the G1-phase RB–E2F complex.\",\n      \"evidence\": \"Co-immunoprecipitation, gel mobility shift, and cell cycle fractionation; cyclin E-specific antisera\",\n      \"pmids\": [\"1531040\", \"1530885\", \"1532457\", \"1532458\", \"1398067\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Identity of the E2F partner not yet established as E2F-4\", \"Functional output of cyclin binding undefined\"]\n    },\n    {\n      \"year\": 1992,\n      \"claim\": \"Mapped cyclin A binding to the unique spacer between the pocket A/B sub-segments, revealing a structural feature absent from pRB that enables direct cyclin recruitment.\",\n      \"evidence\": \"In vitro binding assay with pocket domain mutants\",\n      \"pmids\": [\"1532457\", \"1532458\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether cyclin binding modulates kinase activity not yet tested\"]\n    },\n    {\n      \"year\": 1993,\n      \"claim\": \"Demonstrated p107 is a functional E2F repressor and growth suppressor, and that its E1A-independent mutants still inhibit proliferation, establishing mechanistic divergence from pRB.\",\n      \"evidence\": \"Transient transfection reporter assays, proliferation and flow cytometry assays, Gal4-tethering, monoclonal antibody Co-IP\",\n      \"pmids\": [\"8319904\", \"8458319\", \"8230483\", \"7685208\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"E2F partner identity still inferred as 62-65 kDa phosphoprotein\", \"Cell-type specificity of repression unexplained\"]\n    },\n    {\n      \"year\": 1994,\n      \"claim\": \"Identified E2F-4 as the specific p107 partner and c-Myc as a direct non-E2F target, broadening p107's repertoire beyond E2F to a second proliferation-driving transcription factor.\",\n      \"evidence\": \"Co-IP, reporter and transformation assays, growth rescue experiments\",\n      \"pmids\": [\"7958925\", \"7958924\", \"8076603\", \"8146655\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Promoter-level mechanism of c-Myc repression not defined\", \"Relative contribution of E2F vs c-Myc repression to arrest unclear\"]\n    },\n    {\n      \"year\": 1995,\n      \"claim\": \"Defined two independent growth-suppression domains — an E2F-binding pocket and a p21-related cyclin/cdk2-inhibitory spacer — establishing p107 as a direct CDK inhibitor whose binding is mutually exclusive with p21.\",\n      \"evidence\": \"In vitro kinase inhibition, competitive binding, deletion mutant growth assays, DNA damage treatment\",\n      \"pmids\": [\"7622038\", \"7743997\", \"7799940\", \"8668177\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Precise cyclin-binding residues not yet mapped\", \"In vivo significance of CDK inhibition vs E2F repression not resolved\"]\n    },\n    {\n      \"year\": 1995,\n      \"claim\": \"Showed that cyclin D1/cdk4 (not cyclin E/cdk2) phosphorylates p107 in mid-G1 to dissociate it from E2F-4 and inactivate its G1 block, establishing the upstream switch controlling p107 activity.\",\n      \"evidence\": \"In vivo phosphorylation, dominant-negative cdk4, Co-IP, cell synchronization\",\n      \"pmids\": [\"7797074\", \"8643455\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Specific phosphorylation sites not yet identified\", \"Reversal/dephosphorylation mechanism unknown\"]\n    },\n    {\n      \"year\": 1995,\n      \"claim\": \"Extended p107's repressive reach to Sp1 and defined an E2F-dependent autoregulatory loop at its own promoter, showing distinct domains for distinct transcription-factor targets.\",\n      \"evidence\": \"Endogenous Co-IP, Gal4-Sp1 reporter assays, promoter deletion and site-directed mutagenesis\",\n      \"pmids\": [\"7565695\", \"7791762\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Physiological role of Sp1 repression unclear\", \"Autoregulatory loop tested only in reporter context\"]\n    },\n    {\n      \"year\": 1996,\n      \"claim\": \"Provided the in vivo genetic framework: p107 is dispensable alone but redundant with p130 in chondrocyte/bone development and overlapping with pRB, with combined loss causing lethality and dysplasia.\",\n      \"evidence\": \"Single and compound knockout mice, histology, MEF analysis, E2F partner-switching immunoprecipitation survey\",\n      \"pmids\": [\"8682294\", \"8682293\", \"8657117\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular basis of functional redundancy with p130 not dissected\", \"Tissue-specific target genes undefined\"]\n    },\n    {\n      \"year\": 1997,\n      \"claim\": \"Expanded p107 function to RNA Pol III repression via TFIIIB and rigorously confirmed stoichiometric CDK inhibition through a conserved N-terminal domain, separating it from E2F binding.\",\n      \"evidence\": \"In vitro reconstitution with purified proteins, pull-down, endogenous complex purification, double-KO MEFs\",\n      \"pmids\": [\"10330166\", \"9199292\", \"8627752\", \"9271376\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Physiological signals coupling p107 to Pol III regulation unclear\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Quantified p107 as a dual cyclin/cdk2 inhibitor with two cyclin-binding sites of distinct function, and demonstrated it acts as a tumor suppressor in the retina in a pRB-null background.\",\n      \"evidence\": \"In vitro Ki determination, domain mutant analysis, peptide competition, chimeric mouse histopathology\",\n      \"pmids\": [\"9710622\", \"9620848\", \"9563849\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Human retinoblastoma relevance not directly established\", \"Tissue restriction of tumor suppression unexplained\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Identified PP2A (via the PR59 regulatory subunit) and C/EBPalpha as p107-specific regulators, defining the phosphatase that reactivates p107 and a differentiation-linked complex disruptor.\",\n      \"evidence\": \"Yeast two-hybrid, Co-IP, dephosphorylation and cell cycle assays, EMSA disruption with purified C/EBPalpha\",\n      \"pmids\": [\"9927208\", \"10082561\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"PP2A targeting specificity to p107 vs p130 not fully defined\", \"In vivo role of PR59 untested\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Mapped the four cyclin D1/cdk4 phosphorylation sites and revealed a TGFβ signal-transduction role, positioning p107 within a cytoplasmic Smad3/E2F4/DP1 complex that represses c-myc upon nuclear translocation.\",\n      \"evidence\": \"In vitro kinase assay with site-directed mutagenesis, phosphopeptide mapping, Co-IP, fractionation, ChIP, reporter assays\",\n      \"pmids\": [\"11884610\", \"12150994\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Coordination between CDK phosphorylation and TGFβ complex assembly unresolved\", \"Generality of Smad-E2F site beyond c-myc unclear\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Established stress-responsive PP2A-mediated p107 dephosphorylation as a route to growth arrest, with PP2A physically bound to p107 and activated by oxidative and UV stress.\",\n      \"evidence\": \"Co-IP, phosphatase inhibitor and SV40 small t experiments, in vitro dephosphorylation, p53/p21-null fibroblasts\",\n      \"pmids\": [\"12621062\", \"9989818\", \"15467457\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Specific PP2A regulatory subunit for stress responses not pinned down\", \"Signal relay from stress sensor to PP2A unknown\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Placed p107 (with p130) as a critical effector of FGF growth inhibition in chondrocytes and as a repressor of Notch1 controlling neural stem cell self-renewal, linking it to differentiation-stage decisions.\",\n      \"evidence\": \"Compound knockout mice, chondrocyte/metatarsal organ culture, neurosphere assays, BrdU labeling, ChIP\",\n      \"pmids\": [\"12177046\", \"15353549\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct chondrocyte target genes of p107 undefined\", \"Mechanism coupling FGF to p107 dephosphorylation not detailed\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Connected p107 to the SCF-Skp2/p27 axis and to G2/M gene repression after DNA damage, and revealed it opposes pRB in adipocyte fate by indirect regulation of PGC-1alpha.\",\n      \"evidence\": \"Knockout and overexpression fibroblasts, Skp2 rescue, p27 stability and BrdU assays, gene expression profiling, ChIP on PGC-1alpha promoter\",\n      \"pmids\": [\"15631990\", \"15827088\", \"16271529\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether p107 directly regulates Skp2 transcription unclear\", \"p107 effect on adipose appears indirect via pRB\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Defined p107 as a subunit of cell-cycle-phase-specific LIN-9/MuvB-containing complexes with E2F4 and as a repressor at Hes1, mechanistically linking it to G2/M gene control and neuronal commitment.\",\n      \"evidence\": \"Co-IP across cell cycle, reporter assays, ChIP at Hes1, genetic compound mutant rescue, neuronal birthdating\",\n      \"pmids\": [\"17563750\", \"17591923\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Full composition of the p107-MuvB complex not enumerated\", \"Direct vs indirect Hes1 regulation in vivo not fully separated\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Revealed a context-dependent reversal of p107 function: MAGE-A11 stabilizes p107 and converts it into a transcriptional co-activator of E2F1 in prostate cancer cells.\",\n      \"evidence\": \"Co-IP, ubiquitination assay, siRNA knockdown, reporter assays\",\n      \"pmids\": [\"23853093\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab; structural basis of the activator switch unknown\", \"Physiological prevalence of this mode beyond high-MAGE-A11 tumors unclear\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Refined the DREAM-complex model showing p107 cooperates with p130 to specifically repress G2/M genes after p53 activation, distinct from pRB/p130 repression of G1/S genes.\",\n      \"evidence\": \"Genome-wide expression profiling in primary human fibroblasts with RB-family knockdowns and DNA damage\",\n      \"pmids\": [\"31667499\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct DREAM subunit interactions of p107 not biochemically resolved here\", \"Determinants of G2/M vs G1/S target selectivity unknown\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How the multiple regulatory inputs (CDK phosphorylation, PP2A dephosphorylation, MAGE-A11 stabilization, TGFβ/FGF signaling) are integrated to switch p107 between repressor and activator states across tissues remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unified structural model of phospho-regulated p107 states\", \"Tissue-specific target gene maps incomplete\", \"Human disease relevance beyond mouse retinoblastoma underexplored\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140110\", \"supporting_discovery_ids\": [4, 7, 9, 10, 16, 22, 32]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [11, 23, 27]},\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [11, 23, 27]},\n      {\"term_id\": \"GO:0060089\", \"supporting_discovery_ids\": [32, 34]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [1, 4, 32]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [32]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [1, 3, 4, 11, 13, 40, 45]},\n      {\"term_id\": \"R-HSA-74160\", \"supporting_discovery_ids\": [4, 10, 16, 22, 32]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [32, 34]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [19, 26, 38, 43, 41]}\n    ],\n    \"complexes\": [\n      \"p107–E2F4–cyclin/cdk2 complex\",\n      \"DREAM complex\",\n      \"LIN-9/MuvB complex\",\n      \"Smad3–E2F4/5–DP1–p107 complex\"\n    ],\n    \"partners\": [\n      \"E2F4\",\n      \"CCNA2\",\n      \"CCNE1\",\n      \"CDK2\",\n      \"MYC\",\n      \"SP1\",\n      \"CCND1\",\n      \"PPP2CA\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":5,"faith_total":5,"faith_pct":100.0}}