{"gene":"GYS2","run_date":"2026-06-10T01:55:21","timeline":{"discoveries":[{"year":2010,"finding":"CLOCK protein drives transcriptional activation of Gys2 via two tandemly located E-box elements in the Gys2 promoter, and CLOCK binds these E-box elements in liver chromatin in vivo, thereby regulating circadian rhythms of hepatic glycogen synthesis.","method":"Transient reporter assay, chromatin immunoprecipitation (ChIP) of liver tissue, real-time reporter assay, Clock mutant mouse model","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal ChIP in vivo, reporter assays, and genetic (Clock mutant) evidence from a single rigorous study with multiple orthogonal methods","pmids":["20430893"],"is_preprint":false},{"year":2013,"finding":"PER2 promotes hepatic glycogen storage by interacting with genomic regions of Gys2 (as well as PTG and GL) to induce their expression; Per2-deficient mice show reduced hepatic glycogen synthase protein levels during refeeding, indicating PER2 is required for the feeding-induced transcriptional response of Gys2.","method":"Chromatin immunoprecipitation (ChIP), Per2(Brdm1) knockout mouse model, protein quantification during controlled fasting/refeeding, glycogen phosphorylase activity assay","journal":"Molecular metabolism","confidence":"High","confidence_rationale":"Tier 2 / Moderate — ChIP plus genetic KO model with multiple metabolic readouts in a single focused study","pmids":["24049741"],"is_preprint":false},{"year":2018,"finding":"GYS2 protein competitively binds MDM2 to prevent MDM2-mediated ubiquitination and degradation of p53, and also enhances p300-induced acetylation of p53 at K373/382; in turn, p53 represses GYS2 transcription via the HBx/HDAC1 complex, forming a negative feedback loop.","method":"Co-immunoprecipitation, overexpression and knockdown in vitro and in vivo tumor models, ubiquitination assay, acetylation assay","journal":"Cancer research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple biochemical assays (Co-IP, ubiquitination, acetylation) from a single lab with in vitro and in vivo validation","pmids":["30584071"],"is_preprint":false},{"year":2018,"finding":"In human endometrial epithelial cells, insulin increases GYS2 gene expression 3.7-fold and inactivates GSK3α/β (relieving inhibition of glycogen synthase), resulting in a 4.4-fold increase in intracellular glycogen; progesterone does not alter glycogen content, establishing insulin—not progesterone—as the direct regulator of GYS2-dependent glycogen synthesis in this tissue.","method":"Primary human endometrial epithelial cell culture, insulin/MPA treatment, intracellular glycogen quantification, enzyme activity/phosphorylation assays, gene expression analysis","journal":"The Journal of clinical endocrinology and metabolism","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional cell-based assay with multiple biochemical readouts (glycogen content, GSK3 phosphorylation, GYS2 mRNA) in primary human cells, single lab","pmids":["29726999"],"is_preprint":false},{"year":2023,"finding":"BMAL1 directly binds to promoter and intron regions of Gys2 in mouse liver (validated by ChIP-seq), and hepatocyte-specific Bmal1 knockout abolishes the circadian rhythmic expression of Gys2 and reduces its overall expression level; overexpression of GYS2 in HepG2 cells inhibits proliferation and migration with elevated p53 expression.","method":"ChIP-seq (public datasets), L-Bmal1-/- mouse model, real-time quantitative PCR over 24-h time course, CCK8 proliferation assay, wound healing assay","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP-seq plus genetic KO model with time-course qPCR and functional cell assays, single study","pmids":["38183795"],"is_preprint":false},{"year":2013,"finding":"Comparative sequencing of the Gys2 coding region across Old World and New World fruit bat species identified three parallel amino acid substitutions (Q72H, K371Q, E666D); natural selection drove two of these substitutions (Q72H and E666D), indicating that GYS2 underwent parallel adaptive evolution in frugivorous bats related to carbohydrate metabolism.","method":"Coding-region sequencing of Gys2 across bat species, phylogenetic tests for positive/parallel selection","journal":"Journal of molecular evolution","confidence":"Low","confidence_rationale":"Tier 4 / Weak — computational/evolutionary analysis only, no functional biochemical validation of specific substitutions","pmids":["24258790"],"is_preprint":false}],"current_model":"GYS2 (liver glycogen synthase 2) is the rate-limiting enzyme of hepatic glycogen synthesis whose transcription is under circadian control via direct CLOCK-E-box and PER2-mediated mechanisms; insulin upregulates GYS2 expression through a non-canonical transcriptional pathway (distinct from acute GSK3 inactivation) in endometrial cells; and GYS2 protein participates in a p53 regulatory circuit by competitively binding MDM2 to prevent p53 ubiquitination and by enhancing p300-mediated p53 acetylation, with p53 in turn repressing GYS2 transcription to form a negative feedback loop relevant to hepatocellular carcinoma suppression."},"narrative":{"mechanistic_narrative":"GYS2 is the hepatic glycogen synthase that catalyzes glycogen synthesis and serves as a transcriptionally controlled node coupling feeding state and the circadian clock to glycogen storage [PMID:20430893, PMID:24049741]. Its transcription is directly driven by the core clock machinery: CLOCK binds two tandem E-box elements in the Gys2 promoter to impose circadian rhythmicity on hepatic glycogen synthesis [PMID:20430893], BMAL1 binds Gys2 promoter and intron regions with hepatocyte-specific Bmal1 loss abolishing this rhythmic expression [PMID:38183795], and PER2 associates with the Gys2 locus to drive the feeding-induced transcriptional response, such that Per2-deficient livers show reduced glycogen synthase during refeeding [PMID:24049741]. Beyond classical GSK3-dependent acute control, insulin upregulates GYS2 transcription—shown in human endometrial epithelial cells where insulin both increases GYS2 mRNA and inactivates GSK3α/β to raise intracellular glycogen [PMID:29726999]. GYS2 protein additionally functions in a tumor-suppressive p53 circuit in liver: it competitively binds MDM2 to block MDM2-mediated p53 ubiquitination and enhances p300-induced acetylation of p53 at K373/382, while p53 reciprocally represses GYS2 transcription via an HBx/HDAC1 complex, forming a negative feedback loop, and GYS2 overexpression suppresses hepatoma cell proliferation and migration with elevated p53 [PMID:30584071, PMID:38183795].","teleology":[{"year":2010,"claim":"Established that Gys2 transcription is under direct circadian clock control, explaining the daily rhythm of hepatic glycogen synthesis rather than treating GYS2 as a purely metabolically regulated enzyme.","evidence":"Reporter assays, in vivo liver ChIP for CLOCK at tandem E-boxes, and Clock mutant mice","pmids":["20430893"],"confidence":"High","gaps":["Does not resolve how clock-driven transcription integrates with acute post-translational control of GYS2 activity","Did not test BMAL1 contribution directly"]},{"year":2013,"claim":"Showed that the clock component PER2 is required for the feeding-induced transcriptional response of Gys2, linking nutrient timing to glycogen storage capacity.","evidence":"ChIP at Gys2 genomic regions, Per2(Brdm1) knockout mice, and protein/activity readouts across fasting-refeeding","pmids":["24049741"],"confidence":"High","gaps":["Mechanism by which PER2 promotes rather than represses transcription at this locus not defined","Coordination with CLOCK/BMAL1 binding not directly mapped"]},{"year":2013,"claim":"Provided evolutionary evidence that GYS2 coding sequence was a target of adaptive selection in fruit bats, implicating it in dietary carbohydrate adaptation.","evidence":"Comparative coding-region sequencing across bat species with phylogenetic selection tests","pmids":["24258790"],"confidence":"Low","gaps":["Computational only; no functional validation of Q72H, K371Q, or E666D substitutions on enzyme activity","No mechanistic link to glycogen synthesis rate established"]},{"year":2018,"claim":"Defined a non-enzymatic role for GYS2 protein in stabilizing p53, expanding GYS2 from a metabolic enzyme to a tumor-suppressive signaling component in hepatocellular carcinoma.","evidence":"Co-IP, ubiquitination and acetylation assays, and overexpression/knockdown in vitro and in vivo tumor models","pmids":["30584071"],"confidence":"Medium","gaps":["Single-lab biochemistry without reciprocal independent confirmation of the MDM2-competition mechanism","Structural basis of GYS2-MDM2 binding unresolved","Whether catalytic activity is required for p53 stabilization untested"]},{"year":2018,"claim":"Demonstrated that insulin upregulates GYS2 transcriptionally in addition to relieving GSK3 inhibition, identifying insulin (not progesterone) as the regulator of glycogen synthesis in endometrial epithelium.","evidence":"Primary human endometrial epithelial cells with insulin/MPA treatment, glycogen quantification, GSK3 phosphorylation, and GYS2 mRNA measurement","pmids":["29726999"],"confidence":"Medium","gaps":["Transcription factor mediating insulin-induced GYS2 expression not identified","Generalizability beyond endometrial tissue not tested"]},{"year":2023,"claim":"Confirmed BMAL1 as a direct positive regulator of rhythmic Gys2 expression and connected GYS2 to growth suppression, tying the circadian and p53 axes together.","evidence":"ChIP-seq, hepatocyte-specific Bmal1 knockout with 24-h qPCR time course, and proliferation/migration assays in HepG2 cells","pmids":["38183795"],"confidence":"Medium","gaps":["Causal link between clock-driven GYS2 levels and p53-dependent tumor suppression not directly demonstrated","Whether reduced rhythmicity alters glycogen flux in vivo not quantified"]},{"year":null,"claim":"How GYS2's enzymatic glycogen-synthesis function mechanistically intersects with its p53-stabilizing role, and the transcription factors mediating insulin's effect, remain undefined.","evidence":"","pmids":[],"confidence":"Low","gaps":["No structural model of GYS2-MDM2 interaction","Insulin-responsive transcriptional pathway for GYS2 unidentified","Integration of circadian, insulin, and p53 inputs on a single GYS2 pool not reconstituted"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0016740","term_label":"transferase activity","supporting_discovery_ids":[0,1,3]}],"localization":[],"pathway":[{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[0,1,3]},{"term_id":"R-HSA-9909396","term_label":"Circadian clock","supporting_discovery_ids":[0,1,4]}],"complexes":[],"partners":["MDM2","TP53","EP300"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P54840","full_name":"Glycogen [starch] synthase, liver","aliases":["Glycogen synthase 2"],"length_aa":703,"mass_kda":81.0,"function":"Glycogen synthase participates in the glycogen biosynthetic process along with glycogenin and glycogen branching enzyme. Extends the primer composed of a few glucose units formed by glycogenin by adding new glucose units to it. In this context, glycogen synthase transfers the glycosyl residue from UDP-Glc to the non-reducing end of alpha-1,4-glucan","subcellular_location":"","url":"https://www.uniprot.org/uniprotkb/P54840/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/GYS2","classification":"Not Classified","n_dependent_lines":0,"n_total_lines":1208,"dependency_fraction":0.0},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/GYS2","total_profiled":1310},"omim":[{"mim_id":"610541","title":"PROTEIN PHOSPHATASE 1, REGULATORY SUBUNIT 3B; PPP1R3B","url":"https://www.omim.org/entry/610541"},{"mim_id":"607406","title":"STARCH-BINDING DOMAIN-CONTAINING PROTEIN 1; STBD1","url":"https://www.omim.org/entry/607406"},{"mim_id":"240600","title":"GLYCOGEN STORAGE DISEASE 0, LIVER; GSD0A","url":"https://www.omim.org/entry/240600"},{"mim_id":"138571","title":"GLYCOGEN SYNTHASE 2; GYS2","url":"https://www.omim.org/entry/138571"},{"mim_id":"138570","title":"GLYCOGEN SYNTHASE 1; GYS1","url":"https://www.omim.org/entry/138570"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enriched","tissue_distribution":"Detected in some","driving_tissues":[{"tissue":"liver","ntpm":162.5}],"url":"https://www.proteinatlas.org/search/GYS2"},"hgnc":{"alias_symbol":[],"prev_symbol":[]},"alphafold":{"accession":"P54840","domains":[{"cath_id":"3.40.50.2000","chopping":"26-284","consensus_level":"high","plddt":95.4096,"start":26,"end":284},{"cath_id":"3.40.50.2000","chopping":"286-377_443-596","consensus_level":"medium","plddt":94.98,"start":286,"end":596}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P54840","model_url":"https://alphafold.ebi.ac.uk/files/AF-P54840-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P54840-F1-predicted_aligned_error_v6.png","plddt_mean":86.69},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=GYS2","jax_strain_url":"https://www.jax.org/strain/search?query=GYS2"},"sequence":{"accession":"P54840","fasta_url":"https://rest.uniprot.org/uniprotkb/P54840.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P54840/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P54840"}},"corpus_meta":[{"pmid":"20430893","id":"PMC_20430893","title":"CLOCK regulates circadian rhythms of hepatic glycogen synthesis through transcriptional activation of Gys2.","date":"2010","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/20430893","citation_count":125,"is_preprint":false},{"pmid":"24049741","id":"PMC_24049741","title":"PER2 promotes glucose storage to liver glycogen during feeding and acute fasting by inducing Gys2 PTG and G L expression.","date":"2013","source":"Molecular metabolism","url":"https://pubmed.ncbi.nlm.nih.gov/24049741","citation_count":62,"is_preprint":false},{"pmid":"30584071","id":"PMC_30584071","title":"A GYS2/p53 Negative Feedback Loop Restricts Tumor Growth in HBV-Related Hepatocellular Carcinoma.","date":"2018","source":"Cancer research","url":"https://pubmed.ncbi.nlm.nih.gov/30584071","citation_count":53,"is_preprint":false},{"pmid":"22951595","id":"PMC_22951595","title":"Genome-wide association study identifies GYS2 as a novel genetic factor for polycystic ovary syndrome through obesity-related condition.","date":"2012","source":"Journal of human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/22951595","citation_count":43,"is_preprint":false},{"pmid":"29726999","id":"PMC_29726999","title":"Insulin Regulates Glycogen Synthesis in Human Endometrial Glands Through Increased GYS2.","date":"2018","source":"The Journal of clinical endocrinology and metabolism","url":"https://pubmed.ncbi.nlm.nih.gov/29726999","citation_count":21,"is_preprint":false},{"pmid":"32395408","id":"PMC_32395408","title":"Hepatic glycogen synthase (GYS2) deficiency: seven novel patients and seven novel variants.","date":"2020","source":"JIMD reports","url":"https://pubmed.ncbi.nlm.nih.gov/32395408","citation_count":12,"is_preprint":false},{"pmid":"23426827","id":"PMC_23426827","title":"Mutational analysis of the GYS2 gene in patients diagnosed with ketotic hypoglycaemia.","date":"2012","source":"Journal of pediatric endocrinology & metabolism : JPEM","url":"https://pubmed.ncbi.nlm.nih.gov/23426827","citation_count":11,"is_preprint":false},{"pmid":"32779500","id":"PMC_32779500","title":"A patient with glycogen storage disease type 0 and a novel sequence variant in GYS2: a case report and literature review.","date":"2020","source":"The Journal of international medical research","url":"https://pubmed.ncbi.nlm.nih.gov/32779500","citation_count":10,"is_preprint":false},{"pmid":"38183795","id":"PMC_38183795","title":"Identification of BMAL1-Regulated circadian genes in mouse liver and their potential association with hepatocellular carcinoma: Gys2 and Upp2 as promising candidates.","date":"2023","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/38183795","citation_count":10,"is_preprint":false},{"pmid":"34026071","id":"PMC_34026071","title":"Lupin protein isolate improves insulin sensitivity and steatohepatitis in vivo and modulates the expression of the Fasn, Gys2, and Gsk3b genes.","date":"2021","source":"Food science & nutrition","url":"https://pubmed.ncbi.nlm.nih.gov/34026071","citation_count":10,"is_preprint":false},{"pmid":"26937415","id":"PMC_26937415","title":"Pediatric patient with hyperketotic hypoglycemia diagnosed with glycogen synthase deficiency due to the novel homozygous mutation in GYS2.","date":"2015","source":"Molecular genetics and metabolism reports","url":"https://pubmed.ncbi.nlm.nih.gov/26937415","citation_count":10,"is_preprint":false},{"pmid":"33489759","id":"PMC_33489759","title":"Novel GYS2 mutations in a Japanese patient with glycogen storage disease type 0a.","date":"2021","source":"Molecular genetics and metabolism reports","url":"https://pubmed.ncbi.nlm.nih.gov/33489759","citation_count":8,"is_preprint":false},{"pmid":"30968641","id":"PMC_30968641","title":"Glycogen storage disease type 0 due to a novel frameshift mutation in glycogen synthase 2 (GYS2) gene in a child presenting with fasting hypoglycemia and postprandial hyperglycemia.","date":"2018","source":"The Turkish journal of pediatrics","url":"https://pubmed.ncbi.nlm.nih.gov/30968641","citation_count":5,"is_preprint":false},{"pmid":"24258790","id":"PMC_24258790","title":"The glycogen synthase 2 gene (Gys2) displays parallel evolution between Old World and New World fruit bats.","date":"2013","source":"Journal of molecular evolution","url":"https://pubmed.ncbi.nlm.nih.gov/24258790","citation_count":4,"is_preprint":false},{"pmid":"32987529","id":"PMC_32987529","title":"Multi-scale modeling identifies the role of p53-Gys2 negative feedback loop in cellular homeostasis.","date":"2020","source":"Mathematical biosciences and engineering : MBE","url":"https://pubmed.ncbi.nlm.nih.gov/32987529","citation_count":2,"is_preprint":false},{"pmid":"29167993","id":"PMC_29167993","title":"Group 3 medulloblastoma in a patient with a GYS2 germline mutation and glycogen storage disease 0a.","date":"2017","source":"Child's nervous system : ChNS : official journal of the International Society for Pediatric Neurosurgery","url":"https://pubmed.ncbi.nlm.nih.gov/29167993","citation_count":2,"is_preprint":false},{"pmid":"39629739","id":"PMC_39629739","title":"Single nucleotide polymorphisms of GYS2 gene and its association with milk production traits of dairy cows.","date":"2024","source":"Animal biotechnology","url":"https://pubmed.ncbi.nlm.nih.gov/39629739","citation_count":1,"is_preprint":false},{"pmid":"37574425","id":"PMC_37574425","title":"Whole-Exome sequencing identifies GYS2 biallelic variants in individuals with suspected epilepsy.","date":"2023","source":"Seizure","url":"https://pubmed.ncbi.nlm.nih.gov/37574425","citation_count":1,"is_preprint":false},{"pmid":"34729754","id":"PMC_34729754","title":"[Glycogen storage syndrome type 0 caused by GYS2 gene variation and phenotypic differences between two siblings].","date":"2021","source":"Zhonghua yi xue yi chuan xue za zhi = Zhonghua yixue yichuanxue zazhi = Chinese journal of medical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/34729754","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":11169,"output_tokens":1630,"usd":0.028979,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":8450,"output_tokens":2429,"usd":0.051487,"stage2_stop_reason":"end_turn"},"total_usd":0.080466,"stage1_batch_id":"msgbatch_01DUPACZi7AAWwuZiUjseQF4","stage2_batch_id":"msgbatch_018yt7chE3f48PEFtDwtj6AE","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2010,\n      \"finding\": \"CLOCK protein drives transcriptional activation of Gys2 via two tandemly located E-box elements in the Gys2 promoter, and CLOCK binds these E-box elements in liver chromatin in vivo, thereby regulating circadian rhythms of hepatic glycogen synthesis.\",\n      \"method\": \"Transient reporter assay, chromatin immunoprecipitation (ChIP) of liver tissue, real-time reporter assay, Clock mutant mouse model\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal ChIP in vivo, reporter assays, and genetic (Clock mutant) evidence from a single rigorous study with multiple orthogonal methods\",\n      \"pmids\": [\"20430893\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"PER2 promotes hepatic glycogen storage by interacting with genomic regions of Gys2 (as well as PTG and GL) to induce their expression; Per2-deficient mice show reduced hepatic glycogen synthase protein levels during refeeding, indicating PER2 is required for the feeding-induced transcriptional response of Gys2.\",\n      \"method\": \"Chromatin immunoprecipitation (ChIP), Per2(Brdm1) knockout mouse model, protein quantification during controlled fasting/refeeding, glycogen phosphorylase activity assay\",\n      \"journal\": \"Molecular metabolism\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP plus genetic KO model with multiple metabolic readouts in a single focused study\",\n      \"pmids\": [\"24049741\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"GYS2 protein competitively binds MDM2 to prevent MDM2-mediated ubiquitination and degradation of p53, and also enhances p300-induced acetylation of p53 at K373/382; in turn, p53 represses GYS2 transcription via the HBx/HDAC1 complex, forming a negative feedback loop.\",\n      \"method\": \"Co-immunoprecipitation, overexpression and knockdown in vitro and in vivo tumor models, ubiquitination assay, acetylation assay\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple biochemical assays (Co-IP, ubiquitination, acetylation) from a single lab with in vitro and in vivo validation\",\n      \"pmids\": [\"30584071\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"In human endometrial epithelial cells, insulin increases GYS2 gene expression 3.7-fold and inactivates GSK3α/β (relieving inhibition of glycogen synthase), resulting in a 4.4-fold increase in intracellular glycogen; progesterone does not alter glycogen content, establishing insulin—not progesterone—as the direct regulator of GYS2-dependent glycogen synthesis in this tissue.\",\n      \"method\": \"Primary human endometrial epithelial cell culture, insulin/MPA treatment, intracellular glycogen quantification, enzyme activity/phosphorylation assays, gene expression analysis\",\n      \"journal\": \"The Journal of clinical endocrinology and metabolism\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional cell-based assay with multiple biochemical readouts (glycogen content, GSK3 phosphorylation, GYS2 mRNA) in primary human cells, single lab\",\n      \"pmids\": [\"29726999\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"BMAL1 directly binds to promoter and intron regions of Gys2 in mouse liver (validated by ChIP-seq), and hepatocyte-specific Bmal1 knockout abolishes the circadian rhythmic expression of Gys2 and reduces its overall expression level; overexpression of GYS2 in HepG2 cells inhibits proliferation and migration with elevated p53 expression.\",\n      \"method\": \"ChIP-seq (public datasets), L-Bmal1-/- mouse model, real-time quantitative PCR over 24-h time course, CCK8 proliferation assay, wound healing assay\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP-seq plus genetic KO model with time-course qPCR and functional cell assays, single study\",\n      \"pmids\": [\"38183795\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Comparative sequencing of the Gys2 coding region across Old World and New World fruit bat species identified three parallel amino acid substitutions (Q72H, K371Q, E666D); natural selection drove two of these substitutions (Q72H and E666D), indicating that GYS2 underwent parallel adaptive evolution in frugivorous bats related to carbohydrate metabolism.\",\n      \"method\": \"Coding-region sequencing of Gys2 across bat species, phylogenetic tests for positive/parallel selection\",\n      \"journal\": \"Journal of molecular evolution\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 4 / Weak — computational/evolutionary analysis only, no functional biochemical validation of specific substitutions\",\n      \"pmids\": [\"24258790\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"GYS2 (liver glycogen synthase 2) is the rate-limiting enzyme of hepatic glycogen synthesis whose transcription is under circadian control via direct CLOCK-E-box and PER2-mediated mechanisms; insulin upregulates GYS2 expression through a non-canonical transcriptional pathway (distinct from acute GSK3 inactivation) in endometrial cells; and GYS2 protein participates in a p53 regulatory circuit by competitively binding MDM2 to prevent p53 ubiquitination and by enhancing p300-mediated p53 acetylation, with p53 in turn repressing GYS2 transcription to form a negative feedback loop relevant to hepatocellular carcinoma suppression.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"GYS2 is the hepatic glycogen synthase that catalyzes glycogen synthesis and serves as a transcriptionally controlled node coupling feeding state and the circadian clock to glycogen storage [#0, #1]. Its transcription is directly driven by the core clock machinery: CLOCK binds two tandem E-box elements in the Gys2 promoter to impose circadian rhythmicity on hepatic glycogen synthesis [#0], BMAL1 binds Gys2 promoter and intron regions with hepatocyte-specific Bmal1 loss abolishing this rhythmic expression [#4], and PER2 associates with the Gys2 locus to drive the feeding-induced transcriptional response, such that Per2-deficient livers show reduced glycogen synthase during refeeding [#1]. Beyond classical GSK3-dependent acute control, insulin upregulates GYS2 transcription—shown in human endometrial epithelial cells where insulin both increases GYS2 mRNA and inactivates GSK3α/β to raise intracellular glycogen [#3]. GYS2 protein additionally functions in a tumor-suppressive p53 circuit in liver: it competitively binds MDM2 to block MDM2-mediated p53 ubiquitination and enhances p300-induced acetylation of p53 at K373/382, while p53 reciprocally represses GYS2 transcription via an HBx/HDAC1 complex, forming a negative feedback loop, and GYS2 overexpression suppresses hepatoma cell proliferation and migration with elevated p53 [#2, #4].\",\n  \"teleology\": [\n    {\n      \"year\": 2010,\n      \"claim\": \"Established that Gys2 transcription is under direct circadian clock control, explaining the daily rhythm of hepatic glycogen synthesis rather than treating GYS2 as a purely metabolically regulated enzyme.\",\n      \"evidence\": \"Reporter assays, in vivo liver ChIP for CLOCK at tandem E-boxes, and Clock mutant mice\",\n      \"pmids\": [\"20430893\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Does not resolve how clock-driven transcription integrates with acute post-translational control of GYS2 activity\", \"Did not test BMAL1 contribution directly\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Showed that the clock component PER2 is required for the feeding-induced transcriptional response of Gys2, linking nutrient timing to glycogen storage capacity.\",\n      \"evidence\": \"ChIP at Gys2 genomic regions, Per2(Brdm1) knockout mice, and protein/activity readouts across fasting-refeeding\",\n      \"pmids\": [\"24049741\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism by which PER2 promotes rather than represses transcription at this locus not defined\", \"Coordination with CLOCK/BMAL1 binding not directly mapped\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Provided evolutionary evidence that GYS2 coding sequence was a target of adaptive selection in fruit bats, implicating it in dietary carbohydrate adaptation.\",\n      \"evidence\": \"Comparative coding-region sequencing across bat species with phylogenetic selection tests\",\n      \"pmids\": [\"24258790\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Computational only; no functional validation of Q72H, K371Q, or E666D substitutions on enzyme activity\", \"No mechanistic link to glycogen synthesis rate established\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Defined a non-enzymatic role for GYS2 protein in stabilizing p53, expanding GYS2 from a metabolic enzyme to a tumor-suppressive signaling component in hepatocellular carcinoma.\",\n      \"evidence\": \"Co-IP, ubiquitination and acetylation assays, and overexpression/knockdown in vitro and in vivo tumor models\",\n      \"pmids\": [\"30584071\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single-lab biochemistry without reciprocal independent confirmation of the MDM2-competition mechanism\", \"Structural basis of GYS2-MDM2 binding unresolved\", \"Whether catalytic activity is required for p53 stabilization untested\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Demonstrated that insulin upregulates GYS2 transcriptionally in addition to relieving GSK3 inhibition, identifying insulin (not progesterone) as the regulator of glycogen synthesis in endometrial epithelium.\",\n      \"evidence\": \"Primary human endometrial epithelial cells with insulin/MPA treatment, glycogen quantification, GSK3 phosphorylation, and GYS2 mRNA measurement\",\n      \"pmids\": [\"29726999\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Transcription factor mediating insulin-induced GYS2 expression not identified\", \"Generalizability beyond endometrial tissue not tested\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Confirmed BMAL1 as a direct positive regulator of rhythmic Gys2 expression and connected GYS2 to growth suppression, tying the circadian and p53 axes together.\",\n      \"evidence\": \"ChIP-seq, hepatocyte-specific Bmal1 knockout with 24-h qPCR time course, and proliferation/migration assays in HepG2 cells\",\n      \"pmids\": [\"38183795\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Causal link between clock-driven GYS2 levels and p53-dependent tumor suppression not directly demonstrated\", \"Whether reduced rhythmicity alters glycogen flux in vivo not quantified\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How GYS2's enzymatic glycogen-synthesis function mechanistically intersects with its p53-stabilizing role, and the transcription factors mediating insulin's effect, remain undefined.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No structural model of GYS2-MDM2 interaction\", \"Insulin-responsive transcriptional pathway for GYS2 unidentified\", \"Integration of circadian, insulin, and p53 inputs on a single GYS2 pool not reconstituted\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0016740\", \"supporting_discovery_ids\": [0, 1, 3]}\n    ],\n    \"localization\": [],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [0, 1, 3]},\n      {\"term_id\": \"R-HSA-9909396\", \"supporting_discovery_ids\": [0, 1, 4]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"MDM2\", \"TP53\", \"EP300\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":4,"faith_total":4,"faith_pct":100.0}}