{"gene":"PER1","run_date":"2026-04-29T11:37:58","timeline":{"discoveries":[{"year":1997,"finding":"RIGUI/PER1 encodes a bHLH/PAS protein 44% homologous to Drosophila period, and is expressed in a circadian pattern in the suprachiasmatic nucleus (SCN); expression continues in constant darkness and shifts proportionally with light/dark cycle changes, establishing PER1 as a mammalian ortholog of the Drosophila period gene.","method":"Molecular cloning, sequence homology analysis, in situ hybridization/Northern blotting under constant darkness and shifted light/dark cycles","journal":"Cell","confidence":"High","confidence_rationale":"Tier 2 — foundational identification paper, highly cited, multiple experimental approaches","pmids":["9323128"],"is_preprint":false},{"year":2001,"finding":"PER1 protein exists in multiple tissue-specific isoforms (48 kDa nuclear form in brain, 55 kDa in kidney); a nuclear 48 kDa isoform follows a daily rhythm in mouse brain. Hypoxia increases PER1 protein levels and PER1 physically interacts with HIF-1α via co-immunoprecipitation, suggesting cross-talk between circadian and hypoxic PAS-domain pathways.","method":"Immunoblotting of nuclear/cytoplasmic fractions, co-immunoprecipitation, tissue fractionation","journal":"FASEB journal","confidence":"Medium","confidence_rationale":"Tier 2/3 — co-IP plus subcellular fractionation in single study","pmids":["11726537"],"is_preprint":false},{"year":1999,"finding":"Per1 mRNA amplitude in the pars tuberalis (PT) encodes photoperiodic time: the duration of the nocturnal melatonin signal is decoded as amplitude of Per1 (and ICER) gene expression in the PT, with short photoperiods greatly attenuating the peak.","method":"In situ hybridization of Per1 expression under long and short photoperiods in Syrian hamsters, manipulation of melatonin signal duration","journal":"PNAS","confidence":"High","confidence_rationale":"Tier 2 — direct in vivo manipulation with quantitative expression readout, replicated across photoperiods","pmids":["10449798"],"is_preprint":false},{"year":2009,"finding":"PER1 physically interacts with the androgen receptor (AR) and inhibits AR transactivation; forced expression of PER1 in LNCaP prostate cancer cells diminishes expression of androgen-sensitive genes and causes growth inhibition and apoptosis.","method":"Co-immunoprecipitation, reporter assays (transactivation), siRNA/overexpression with proliferation and apoptosis readouts","journal":"Cancer research","confidence":"Medium","confidence_rationale":"Tier 2/3 — reciprocal functional assays plus co-IP in single lab","pmids":["19752089"],"is_preprint":false},{"year":2013,"finding":"IRE1α endoribonuclease activity degrades PER1 mRNA post-transcriptionally in tumor cells without affecting PER1 gene transcription; inhibition of IRE1α prevents PER1 mRNA decay and reduces tumorigenesis.","method":"siRNA-mediated silencing, dominant-negative IRE1α strategy, qRT-PCR for mRNA vs. hnRNA, tumor growth assays","journal":"Cancer research","confidence":"High","confidence_rationale":"Tier 1/2 — multiple orthogonal methods (DN mutant + siRNA + hnRNA assay) in single rigorous study","pmids":["23752693"],"is_preprint":false},{"year":2013,"finding":"Per1 and the mineralocorticoid receptor (MR) coordinately regulate αENaC transcription through E-box elements in the αENaC promoter; aldosterone increases Per1 occupancy on the αENaC E-box, and mutation of these E-boxes abolishes both basal and aldosterone-mediated promoter activity.","method":"Site-directed mutagenesis of E-boxes, DNA pull-down assays, chromatin immunoprecipitation (ChIP), reporter assays","journal":"Frontiers in physiology","confidence":"High","confidence_rationale":"Tier 1 — mutagenesis + ChIP + pull-down with functional reporter readout","pmids":["24062694"],"is_preprint":false},{"year":2014,"finding":"Per1 regulates expression of the endothelin axis genes (ET-1, ETA, ETB) in a tissue-specific and time-dependent manner in mouse kidney, lung, liver, and heart.","method":"Quantitative RT-PCR in Per1 heterozygous vs. wild-type mice tissues collected at rest and active phases","journal":"Life sciences","confidence":"Medium","confidence_rationale":"Tier 2 — clean genetic KO model with defined tissue-specific expression phenotype","pmids":["24721511"],"is_preprint":false},{"year":2015,"finding":"Per1 transcriptionally regulates NHE3 and SGLT1 (but not SGLT2) in renal proximal tubule cells; Per1 and CLOCK are detected at the NHE3 and SGLT1 promoters by ChIP, and pharmacological blockade of nuclear Per1 entry or siRNA knockdown decreases both mRNA and protein levels of NHE3 and SGLT1 and reduces Na⁺-K⁺-ATPase activity.","method":"ChIP, siRNA knockdown, pharmacological nuclear entry blockade, heterogeneous nuclear RNA analysis, protein immunoblotting","journal":"American journal of physiology. Renal physiology","confidence":"High","confidence_rationale":"Tier 1/2 — ChIP + siRNA + hnRNA + protein assays, multiple orthogonal approaches","pmids":["26377793"],"is_preprint":false},{"year":2015,"finding":"EGR1 directly binds the proximal Per1 promoter to activate Per1 transcription; CLOCK/BMAL1 heterodimer transactivates Egr1 via a conserved E-box, placing EGR1 as an intermediate regulator of Per1 amplitude in the hepatic clock.","method":"Chromatin immunoprecipitation, luciferase reporter assays, Egr1-deficient mouse model with hepatic clock gene expression analysis","journal":"Scientific reports","confidence":"High","confidence_rationale":"Tier 1/2 — ChIP + reporter assay + in vivo KO model","pmids":["26471974"],"is_preprint":false},{"year":2019,"finding":"The progesterone receptor (PR) directly binds the PER1 promoter to activate PER1 transcription during human endometrial decidualization; PER1 knockout attenuates decidual transformation by accelerating FOXO1 protein degradation.","method":"ChIP assay for PR at PER1 promoter, PER1 knockout in stromal cells, FOXO1 protein stability assays, qRT-PCR","journal":"The Journal of endocrinology","confidence":"High","confidence_rationale":"Tier 1/2 — ChIP + KO with defined cellular phenotype and downstream protein target","pmids":["31518992"],"is_preprint":false},{"year":2021,"finding":"PER2 acts as a co-factor of CREB to facilitate formation of a transactivation complex (CREB/CRTC1/CBP) on the CRE element of the Per1 gene promoter in response to light or forskolin; absence of PER2 abolishes CBP-CREB interaction, reduces histone H3 acetylation, and decreases RNA Pol II recruitment to the Per1 gene.","method":"Co-immunoprecipitation, ChIP, in vitro and in vivo approaches with Per2 knockout, histone acetylation assays, RNA Pol II ChIP","journal":"Scientific reports","confidence":"High","confidence_rationale":"Tier 1/2 — multiple orthogonal methods (co-IP, ChIP, histone modification, KO) in single study","pmids":["34741086"],"is_preprint":false},{"year":2021,"finding":"PER1 physically interacts with p53, reducing p53 stability and impairing its transcriptional activity; conversely, p53 represses PER1 transcription. PER1 overexpression reduces cancer cell sensitivity to drug-induced apoptosis in vitro and in vivo in xenograft models.","method":"Co-immunoprecipitation, reporter assays, overexpression/knockdown with apoptosis readouts, xenograft mouse model","journal":"International journal of molecular sciences","confidence":"Medium","confidence_rationale":"Tier 2/3 — co-IP + functional assays in single lab","pmids":["33804124"],"is_preprint":false},{"year":2022,"finding":"PER1 forms a transcriptional complex with PPARγ to regulate circadian oscillation of HK2 expression; silencing PER1 disrupts the circadian rhythm of HK2-dependent glycolysis and reverses trastuzumab resistance in gastric cancer cells.","method":"Co-immunoprecipitation, siRNA knockdown, in vitro and in vivo glycolysis assays, chronotherapy experiments","journal":"Cancer research","confidence":"Medium","confidence_rationale":"Tier 2/3 — co-IP + functional in vitro/in vivo assays in single lab","pmids":["35255118"],"is_preprint":false},{"year":2022,"finding":"PER1 binds to HIF-1α protein to promote HIF-1α protein degradation (shown by co-immunoprecipitation and cycloheximide chase); HIF-1α in turn binds the PER1 promoter to feedback-inhibit PER1 transcription (shown by ChIP and dual luciferase assay), forming a PER1/HIF-1α negative feedback loop that promotes ferroptosis in oral squamous cell carcinoma.","method":"Co-immunoprecipitation, cycloheximide chase assay, ChIP, dual luciferase reporter assay, in vivo tumorigenicity assays","journal":"Translational oncology","confidence":"High","confidence_rationale":"Tier 1/2 — multiple orthogonal mechanistic methods (co-IP, CHX chase, ChIP, reporter) in single study","pmids":["35134674"],"is_preprint":false},{"year":2016,"finding":"miR-34a directly targets PER1 mRNA to inhibit its expression; decreased miR-34a leads to increased Per1 levels that suppress cholangiocarcinoma cell proliferation and tumor growth; mRNA profiling shows Per1 overexpression regulates cell cycle, growth, and apoptosis pathways.","method":"Luciferase reporter assay for miRNA targeting, miR-34a inhibition/overexpression, cell proliferation and apoptosis assays, in vivo tumor growth, mRNA profiling","journal":"Journal of hepatology","confidence":"Medium","confidence_rationale":"Tier 2 — validated miRNA target + in vivo and in vitro functional assays","pmids":["26923637"],"is_preprint":false},{"year":2022,"finding":"LncRNA TPTEP1 sponges miR-548d-3p to derepress KLF9, which binds the PER1 promoter to activate PER1 transcription, thereby inhibiting gastric cancer cell migration and invasion.","method":"Luciferase assay for sponge activity and 3'UTR targeting, ChIP for KLF9 binding to PER1 promoter, wound healing and transwell assays, nude mouse xenograft","journal":"Pathology, research and practice","confidence":"Medium","confidence_rationale":"Tier 2/3 — ChIP + luciferase + functional cellular assays","pmids":["35985238"],"is_preprint":false},{"year":2022,"finding":"Per1/Per2 double knockout in mice reduces testosterone synthesis by downregulating steroidogenic enzymes (Cyp11a1, Cyp17a1, Hsd17b3, Hsd3b1, StAR) via impaired PKA-CREB-StAR signaling, leading to decreased sperm motility and reduced fertility in elderly males.","method":"Per1/Per2 double knockout mouse model, hormone-targeted metabolomics, transcriptomic analysis, Western blotting for StAR, p-CREB, PKA, AC1","journal":"International journal of molecular sciences","confidence":"Medium","confidence_rationale":"Tier 2 — genetic KO with defined mechanistic pathway (PKA-StAR) and multiple molecular readouts","pmids":["35806403"],"is_preprint":false},{"year":2023,"finding":"Local knockdown of Per1 within the dorsal hippocampus impairs spatial memory consolidation without affecting circadian rhythm or sleep, demonstrating a local, circuit-level role for Per1 in hippocampal memory independent of its SCN circadian function.","method":"Lentiviral Per1 knockdown in dorsal hippocampus, Object Location Memory behavioral testing, RNA-sequencing for identification of Per1 as learning-induced oscillator","journal":"Neuropsychopharmacology","confidence":"Medium","confidence_rationale":"Tier 2 — targeted in vivo knockdown with specific behavioral phenotype and transcriptomic identification","pmids":["37264172"],"is_preprint":false},{"year":2015,"finding":"In the SCN, PER1-expressing neurons are differentially distributed from PER2-expressing neurons across the rostro-caudal extent, with high PER1 expression concentrated in a broad central area and high PER2 in rostral and caudal portions, suggesting spatially distinct functional roles in circadian timekeeping.","method":"Triple immunofluorescence labeling and automated image analysis of PER1, PER2, and gastrin-releasing peptide in sagittal SCN sections","journal":"The European journal of neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 — direct quantitative protein localization across defined anatomical regions","pmids":["27740710"],"is_preprint":false},{"year":2007,"finding":"Estradiol and progesterone upregulate Per1 expression in specific compartments of the rat uterus (LE, GE, M for estradiol; LE, GE, S for progesterone); effects are blocked by the respective receptor antagonists ICI182780 and RU486, demonstrating steroid hormone regulation of Per1 expression.","method":"In situ hybridization, immunofluorescence, RT-PCR in ovariectomized rats and cultured uterine stromal cells with hormone/antagonist treatment","journal":"The Journal of endocrinology","confidence":"Medium","confidence_rationale":"Tier 2 — in vivo and in vitro evidence with receptor antagonist validation","pmids":["17761890"],"is_preprint":false}],"current_model":"PER1 is a bHLH/PAS-domain circadian clock protein that functions as a transcriptional regulator and co-factor within the core negative feedback loop: it is transcriptionally activated by CLOCK/BMAL1 via E-boxes (with intermediaries including EGR1, PR, and CREB/CRTC1/CBP complexes), repressed post-transcriptionally by IRE1α-mediated mRNA decay, and its protein interacts with HIF-1α (promoting HIF-1α degradation), the androgen receptor (inhibiting AR transactivation), p53 (reducing p53 stability), and PPARγ (co-regulating metabolic gene oscillation), while also co-occupying gene promoters with MR and CLOCK to drive circadian transcription of sodium transport genes (αENaC, NHE3, SGLT1) in the kidney, and independently regulating hippocampal memory consolidation at the local circuit level."},"narrative":{"teleology":[{"year":1997,"claim":"The identification of PER1 (RIGUI) as a bHLH/PAS-domain mammalian ortholog of Drosophila period, with circadian expression in the SCN persisting in constant darkness, established for the first time that mammals possess a molecular clock gene homologous to invertebrate period.","evidence":"Molecular cloning, sequence homology, in situ hybridization and Northern blotting under constant darkness and shifted LD cycles in mouse SCN","pmids":["9323128"],"confidence":"High","gaps":["No loss-of-function data to confirm requirement for circadian rhythmicity","Protein-level rhythmicity not demonstrated","No mechanistic insight into how PER1 feeds back on the clock"]},{"year":1999,"claim":"Demonstrating that Per1 mRNA amplitude in the pars tuberalis encodes photoperiodic time established PER1 as a decoder of melatonin signal duration, extending its role from circadian oscillator to seasonal timer.","evidence":"In situ hybridization of Per1 in Syrian hamster pars tuberalis under long vs. short photoperiods with melatonin signal manipulation","pmids":["10449798"],"confidence":"High","gaps":["Mechanism by which melatonin controls Per1 transcription in PT not defined","Downstream effectors of Per1 amplitude in seasonal physiology unknown"]},{"year":2001,"claim":"Discovery of tissue-specific PER1 isoforms and its physical interaction with HIF-1α revealed cross-talk between circadian PAS-domain proteins and the hypoxia response, though functional consequences were unclear.","evidence":"Immunoblotting of nuclear/cytoplasmic fractions across tissues, co-immunoprecipitation of PER1 and HIF-1α","pmids":["11726537"],"confidence":"Medium","gaps":["Only forward co-IP shown; reciprocal validation absent in original study","Functional impact of PER1–HIF-1α interaction on either pathway not demonstrated","Isoform-specific functions unresolved"]},{"year":2007,"claim":"Showing that estradiol and progesterone regulate Per1 expression in distinct uterine compartments via their cognate receptors established hormonal control of Per1 as a mechanism coupling reproductive steroid signaling to local peripheral clocks.","evidence":"In situ hybridization and RT-PCR in ovariectomized rats with receptor antagonist (ICI182780, RU486) blockade","pmids":["17761890"],"confidence":"Medium","gaps":["Whether steroid hormones directly bind the Per1 promoter or act indirectly was not resolved","Functional consequence of Per1 induction for uterine physiology not tested"]},{"year":2009,"claim":"PER1's physical interaction with the androgen receptor and inhibition of AR transactivation, causing growth arrest and apoptosis in prostate cancer cells, revealed a direct molecular link between the circadian clock protein and hormone-dependent cancer.","evidence":"Co-IP of PER1–AR, reporter assays for AR transactivation, siRNA/overexpression with proliferation and apoptosis readouts in LNCaP cells","pmids":["19752089"],"confidence":"Medium","gaps":["Domain mapping of PER1–AR interaction not performed","Mechanism of growth inhibition downstream of AR repression not delineated","In vivo confirmation with genetic models absent"]},{"year":2013,"claim":"Two parallel discoveries established PER1 as an output transcription factor of the renal clock and as a target of IRE1α-mediated post-transcriptional regulation: PER1 and MR co-regulate αENaC transcription via E-box elements, while IRE1α endonuclease degrades PER1 mRNA post-transcriptionally in tumor cells, providing a mechanism for circadian disruption in cancer.","evidence":"ChIP, E-box mutagenesis, and reporter assays for αENaC regulation; siRNA, dominant-negative IRE1α, and hnRNA assays for post-transcriptional decay","pmids":["24062694","23752693"],"confidence":"High","gaps":["Whether IRE1α cleaves PER1 mRNA directly or via an intermediate is unresolved","αENaC regulation not tested in Per1-null animals"]},{"year":2015,"claim":"Extension of PER1's renal transcriptional targets to NHE3 and SGLT1 — with ChIP confirming PER1 and CLOCK co-occupancy at these promoters — consolidated PER1 as a direct circadian transcriptional regulator of renal sodium transport, and EGR1 was identified as an intermediate transcription factor linking CLOCK/BMAL1 to Per1 promoter activation.","evidence":"ChIP, siRNA, pharmacological nuclear entry blockade, hnRNA analysis for renal targets; ChIP, reporter assays, and Egr1-KO mice for EGR1–Per1 axis","pmids":["26377793","26471974"],"confidence":"High","gaps":["Whether EGR1-mediated Per1 regulation occurs in non-hepatic tissues unknown","Relative contribution of E-box vs. EGR1-binding site to Per1 amplitude not quantified"]},{"year":2016,"claim":"Identification of PER1 as a direct target of miR-34a added a microRNA layer to post-transcriptional clock control and showed that Per1 overexpression suppresses cholangiocarcinoma growth, reinforcing its tumor-suppressive function.","evidence":"Luciferase reporter assay for 3′UTR targeting, miR-34a modulation with in vivo tumor xenograft readouts","pmids":["26923637"],"confidence":"Medium","gaps":["Whether miR-34a regulation of PER1 is circadian phase-dependent not tested","Downstream effectors of PER1-mediated growth suppression in cholangiocarcinoma uncharacterized"]},{"year":2019,"claim":"Progesterone receptor directly binds the PER1 promoter to activate its transcription during endometrial decidualization, and PER1 knockout impairs decidualization by destabilizing FOXO1, revealing a specific reproductive function downstream of PER1.","evidence":"ChIP for PR at PER1 promoter, PER1 knockout in stromal cells with FOXO1 protein stability and decidualization assays","pmids":["31518992"],"confidence":"High","gaps":["Whether FOXO1 stabilization is a direct PER1 protein interaction or transcriptional effect not resolved","Relevance to in vivo fertility phenotypes not demonstrated"]},{"year":2021,"claim":"Two studies deepened PER1's role in transcription factor regulation: PER2 was shown to scaffold CREB/CRTC1/CBP assembly at the Per1 CRE element for light-induced Per1 transcription, and PER1 was found to physically interact with p53, reducing its stability and transcriptional activity, with functional consequences for drug-induced apoptosis.","evidence":"Co-IP, ChIP, histone acetylation, and RNA Pol II ChIP in Per2-KO SCN tissue; co-IP, reporter assays, overexpression/knockdown with xenograft models for PER1–p53","pmids":["34741086","33804124"],"confidence":"High","gaps":["Whether PER1 promotes p53 degradation via ubiquitin-proteasome pathway not established","Domain requirements for PER1–p53 interaction unknown","PER2-mediated Per1 induction mechanism not shown to be conserved in peripheral tissues"]},{"year":2022,"claim":"A cluster of 2022 studies established PER1 as (i) a PPARγ co-factor driving circadian HK2 oscillation and glycolytic drug resistance, (ii) a direct promoter of HIF-1α degradation forming a reciprocal negative feedback loop that controls ferroptosis, (iii) a target of KLF9-mediated transcriptional activation via a lncRNA sponge pathway in gastric cancer, and (iv) a regulator of testosterone biosynthesis through the PKA-CREB-StAR axis.","evidence":"Co-IP, siRNA, glycolysis assays, chronotherapy experiments for PPARγ–PER1; co-IP, CHX chase, ChIP, dual luciferase for PER1–HIF-1α loop; ChIP for KLF9 at PER1 promoter and xenograft assays; Per1/Per2 double-KO mice with hormone metabolomics and PKA-StAR pathway analysis","pmids":["35255118","35134674","35985238","35806403"],"confidence":"Medium","gaps":["PPARγ–PER1 complex composition and DNA-binding mode unresolved","Whether PER1 recruits a specific E3 ligase for HIF-1α degradation is unknown","Per1 vs. Per2 individual contributions to steroidogenesis not separated in double-KO"]},{"year":2023,"claim":"Local knockdown of Per1 in dorsal hippocampus impaired spatial memory consolidation without affecting circadian rhythm or sleep, establishing a non-canonical, circuit-level function for PER1 outside the SCN clock network.","evidence":"Lentiviral Per1 knockdown in dorsal hippocampus with Object Location Memory testing and RNA-seq","pmids":["37264172"],"confidence":"Medium","gaps":["Molecular targets of PER1 in hippocampal memory consolidation not identified","Whether other Period genes compensate or share this function unknown","Electrophysiological correlates of Per1-dependent memory consolidation not explored"]},{"year":null,"claim":"Key unresolved questions include: the structural basis of PER1's interaction with its diverse protein partners (AR, HIF-1α, p53, PPARγ), whether PER1 recruits specific ubiquitin ligases for target degradation, how tissue-specific isoforms (48 vs. 55 kDa) differ functionally, and the full scope of PER1's non-circadian roles in memory and reproduction.","evidence":"","pmids":[],"confidence":"Low","gaps":["No crystal or cryo-EM structure of PER1 in complex with any partner","Isoform-specific functions remain entirely uncharacterized","No genome-wide PER1 ChIP-seq in peripheral tissues to define direct target gene repertoire"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140110","term_label":"transcription regulator activity","supporting_discovery_ids":[5,7,9,12,13]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[3,11,13]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[1,5,7]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[1]}],"pathway":[{"term_id":"R-HSA-9909396","term_label":"Circadian clock","supporting_discovery_ids":[0,2,5,7,8,10,18]},{"term_id":"R-HSA-74160","term_label":"Gene expression (Transcription)","supporting_discovery_ids":[5,7,8,9,12,13]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[3,11,13,19]},{"term_id":"R-HSA-382551","term_label":"Transport of small molecules","supporting_discovery_ids":[5,7]},{"term_id":"R-HSA-1474165","term_label":"Reproduction","supporting_discovery_ids":[9,16]}],"complexes":["PER1–CLOCK transcriptional complex","PER1–PPARγ transcriptional complex"],"partners":["CLOCK","HIF1A","AR","TP53","PPARG","NR3C2","EGR1","PGR"],"other_free_text":[]},"mechanistic_narrative":"PER1 is a core component of the mammalian circadian clock that functions both as a transcriptional co-regulator within the negative feedback loop and as a versatile protein–protein interaction hub linking circadian timing to metabolism, hormone signaling, hypoxia, and tumor suppression. Identified as the mammalian ortholog of Drosophila period, PER1 is rhythmically expressed in the suprachiasmatic nucleus and peripheral tissues, is transcriptionally activated by CLOCK/BMAL1 via E-box elements and additional regulators including EGR1, progesterone receptor, and the PER2-dependent CREB/CRTC1/CBP complex, and is post-transcriptionally regulated by IRE1α-mediated mRNA decay and miR-34a targeting [PMID:9323128, PMID:24062694, PMID:26471974, PMID:31518992, PMID:34741086, PMID:23752693, PMID:26923637]. At the effector level, PER1 occupies E-box-containing promoters together with CLOCK to drive circadian transcription of renal sodium transport genes (αENaC, NHE3, SGLT1), forms complexes with PPARγ to regulate glycolytic gene oscillation, promotes HIF-1α protein degradation, inhibits androgen receptor transactivation, and reduces p53 stability, thereby influencing cell proliferation, apoptosis, ferroptosis, and drug resistance [PMID:26377793, PMID:35255118, PMID:35134674, PMID:19752089, PMID:33804124]. Beyond its canonical circadian role, local Per1 expression in the dorsal hippocampus is required for spatial memory consolidation independent of SCN-driven rhythms [PMID:37264172]."},"prefetch_data":{"uniprot":{"accession":"O15534","full_name":"Period circadian protein homolog 1","aliases":["Circadian clock protein PERIOD 1","Circadian pacemaker protein Rigui"],"length_aa":1290,"mass_kda":136.2,"function":"Transcriptional repressor which forms a core component of the circadian clock. The circadian clock, an internal time-keeping system, regulates various physiological processes through the generation of approximately 24 hour circadian rhythms in gene expression, which are translated into rhythms in metabolism and behavior. It is derived from the Latin roots 'circa' (about) and 'diem' (day) and acts as an important regulator of a wide array of physiological functions including metabolism, sleep, body temperature, blood pressure, endocrine, immune, cardiovascular, and renal function. Consists of two major components: the central clock, residing in the suprachiasmatic nucleus (SCN) of the brain, and the peripheral clocks that are present in nearly every tissue and organ system. Both the central and peripheral clocks can be reset by environmental cues, also known as Zeitgebers (German for 'timegivers'). The predominant Zeitgeber for the central clock is light, which is sensed by retina and signals directly to the SCN. The central clock entrains the peripheral clocks through neuronal and hormonal signals, body temperature and feeding-related cues, aligning all clocks with the external light/dark cycle. Circadian rhythms allow an organism to achieve temporal homeostasis with its environment at the molecular level by regulating gene expression to create a peak of protein expression once every 24 hours to control when a particular physiological process is most active with respect to the solar day. Transcription and translation of core clock components (CLOCK, NPAS2, BMAL1, BMAL2, PER1, PER2, PER3, CRY1 and CRY2) plays a critical role in rhythm generation, whereas delays imposed by post-translational modifications (PTMs) are important for determining the period (tau) of the rhythms (tau refers to the period of a rhythm and is the length, in time, of one complete cycle). A diurnal rhythm is synchronized with the day/night cycle, while the ultradian and infradian rhythms have a period shorter and longer than 24 hours, respectively. Disruptions in the circadian rhythms contribute to the pathology of cardiovascular diseases, cancer, metabolic syndromes and aging. A transcription/translation feedback loop (TTFL) forms the core of the molecular circadian clock mechanism. Transcription factors, CLOCK or NPAS2 and BMAL1 or BMAL2, form the positive limb of the feedback loop, act in the form of a heterodimer and activate the transcription of core clock genes and clock-controlled genes (involved in key metabolic processes), harboring E-box elements (5'-CACGTG-3') within their promoters. The core clock genes: PER1/2/3 and CRY1/2 which are transcriptional repressors form the negative limb of the feedback loop and interact with the CLOCK|NPAS2-BMAL1|BMAL2 heterodimer inhibiting its activity and thereby negatively regulating their own expression. This heterodimer also activates nuclear receptors NR1D1/2 and RORA/B/G, which form a second feedback loop and which activate and repress BMAL1 transcription, respectively. Regulates circadian target genes expression at post-transcriptional levels, but may not be required for the repression at transcriptional level. Controls PER2 protein decay. Represses CRY2 preventing its repression on CLOCK/BMAL1 target genes such as FXYD5 and SCNN1A in kidney and PPARA in liver. Besides its involvement in the maintenance of the circadian clock, has an important function in the regulation of several processes. Participates in the repression of glucocorticoid receptor NR3C1/GR-induced transcriptional activity by reducing the association of NR3C1/GR to glucocorticoid response elements (GREs) by BMAL1:CLOCK. Plays a role in the modulation of the neuroinflammatory state via the regulation of inflammatory mediators release, such as CCL2 and IL6. In spinal astrocytes, negatively regulates the MAPK14/p38 and MAPK8/JNK MAPK cascades as well as the subsequent activation of NFkappaB. Coordinately regulates the expression of multiple genes that are involved in the regulation of renal sodium reabsorption. Can act as gene expression activator in a gene and tissue specific manner, in kidney enhances WNK1 and SLC12A3 expression in collaboration with CLOCK. Modulates hair follicle cycling. 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toxicology","url":"https://pubmed.ncbi.nlm.nih.gov/37817473","citation_count":21,"is_preprint":false},{"pmid":"33129602","id":"PMC_33129602","title":"Exposure to per- and polyfluoroalkyl substances and premature skin aging.","date":"2020","source":"Journal of hazardous materials","url":"https://pubmed.ncbi.nlm.nih.gov/33129602","citation_count":21,"is_preprint":false},{"pmid":"34968493","id":"PMC_34968493","title":"Per- and polyfluoroalkyl substances target and alter human prostate stem-progenitor cells.","date":"2021","source":"Biochemical pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/34968493","citation_count":21,"is_preprint":false},{"pmid":"38377926","id":"PMC_38377926","title":"Removal of per- and polyfluoroalkyl substances from water by plasma treatment: Insights into structural effects and underlying mechanisms.","date":"2024","source":"Water research","url":"https://pubmed.ncbi.nlm.nih.gov/38377926","citation_count":21,"is_preprint":false},{"pmid":"36084455","id":"PMC_36084455","title":"Glioma is associated with exposure to legacy and alternative per- and polyfluoroalkyl substances.","date":"2022","source":"Journal of hazardous materials","url":"https://pubmed.ncbi.nlm.nih.gov/36084455","citation_count":20,"is_preprint":false},{"pmid":"18593875","id":"PMC_18593875","title":"PERspective on PER phosphorylation.","date":"2008","source":"Genes & development","url":"https://pubmed.ncbi.nlm.nih.gov/18593875","citation_count":20,"is_preprint":false},{"pmid":"38977121","id":"PMC_38977121","title":"Immunotoxicity of legacy and alternative per- and polyfluoroalkyl substances on zebrafish larvae.","date":"2024","source":"Environmental pollution (Barking, Essex : 1987)","url":"https://pubmed.ncbi.nlm.nih.gov/38977121","citation_count":19,"is_preprint":false},{"pmid":"37142081","id":"PMC_37142081","title":"Dietary per- and polyfluoroalkyl substance (PFAS) exposure in adolescents: The HOME study.","date":"2023","source":"Environmental research","url":"https://pubmed.ncbi.nlm.nih.gov/37142081","citation_count":19,"is_preprint":false},{"pmid":"37648245","id":"PMC_37648245","title":"Novel Per- and Polyfluoroalkyl Substances Discovered in Cattle Exposed to AFFF-Impacted Groundwater.","date":"2023","source":"Environmental science & technology","url":"https://pubmed.ncbi.nlm.nih.gov/37648245","citation_count":19,"is_preprint":false},{"pmid":"37633367","id":"PMC_37633367","title":"Comparative developmental toxicities of zebrafish towards structurally diverse per- and polyfluoroalkyl substances.","date":"2023","source":"The Science of the total environment","url":"https://pubmed.ncbi.nlm.nih.gov/37633367","citation_count":19,"is_preprint":false},{"pmid":"26656624","id":"PMC_26656624","title":"Real-Time Recording of Circadian Per1 and Per2 Expression in the Suprachiasmatic Nucleus of Freely Moving Rats.","date":"2015","source":"Journal of biological rhythms","url":"https://pubmed.ncbi.nlm.nih.gov/26656624","citation_count":18,"is_preprint":false},{"pmid":"35806403","id":"PMC_35806403","title":"Per1/Per2 Disruption Reduces Testosterone Synthesis and Impairs Fertility in Elderly Male Mice.","date":"2022","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/35806403","citation_count":17,"is_preprint":false},{"pmid":"36055240","id":"PMC_36055240","title":"Toxicokinetic Modeling of Per- and Polyfluoroalkyl Substance Concentrations within Developing Zebrafish (Danio rerio) Populations.","date":"2022","source":"Environmental science & technology","url":"https://pubmed.ncbi.nlm.nih.gov/36055240","citation_count":17,"is_preprint":false},{"pmid":"36777525","id":"PMC_36777525","title":"Early-life exposure to per- and polyfluoroalkyl substances and infant gut microbial composition.","date":"2022","source":"Environmental epidemiology (Philadelphia, Pa.)","url":"https://pubmed.ncbi.nlm.nih.gov/36777525","citation_count":16,"is_preprint":false},{"pmid":"27740710","id":"PMC_27740710","title":"Differential localization of PER1 and PER2 in the brain master circadian clock.","date":"2016","source":"The European journal of neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/27740710","citation_count":16,"is_preprint":false},{"pmid":"38782768","id":"PMC_38782768","title":"Identifying novel mechanisms of per- and polyfluoroalkyl substance-induced hepatotoxicity using FRG humanized mice.","date":"2024","source":"Archives of toxicology","url":"https://pubmed.ncbi.nlm.nih.gov/38782768","citation_count":15,"is_preprint":false},{"pmid":"39467433","id":"PMC_39467433","title":"Aerobic or anaerobic? Microbial degradation of per- and polyfluoroalkyl substances: A review.","date":"2024","source":"Journal of hazardous materials","url":"https://pubmed.ncbi.nlm.nih.gov/39467433","citation_count":15,"is_preprint":false},{"pmid":"36638633","id":"PMC_36638633","title":"Per- and polyfluoroalkyl substances (PFAS) inhibit cytochrome P450 CYP3A7 through direct coordination to the heme iron and water displacement.","date":"2023","source":"Journal of inorganic biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/36638633","citation_count":15,"is_preprint":false},{"pmid":"35985238","id":"PMC_35985238","title":"LncRNA TPTEP1 inhibits the migration and invasion of gastric cancer cells through miR-548d-3p/KLF9/PER1 axis.","date":"2022","source":"Pathology, research and practice","url":"https://pubmed.ncbi.nlm.nih.gov/35985238","citation_count":15,"is_preprint":false},{"pmid":"20227883","id":"PMC_20227883","title":"Cell biology through proteomics--ad astra per alia porci.","date":"2010","source":"Trends in cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/20227883","citation_count":15,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":51131,"output_tokens":4493,"usd":0.110394},"stage2":{"model":"claude-opus-4-6","input_tokens":8061,"output_tokens":3734,"usd":0.200483},"total_usd":0.310877,"stage1_batch_id":"msgbatch_012ZiiCUBfB62NCTQd4Bk1Jo","stage2_batch_id":"msgbatch_01Xuqq9aUHoQouS7UVGZNStZ","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1997,\n      \"finding\": \"RIGUI/PER1 encodes a bHLH/PAS protein 44% homologous to Drosophila period, and is expressed in a circadian pattern in the suprachiasmatic nucleus (SCN); expression continues in constant darkness and shifts proportionally with light/dark cycle changes, establishing PER1 as a mammalian ortholog of the Drosophila period gene.\",\n      \"method\": \"Molecular cloning, sequence homology analysis, in situ hybridization/Northern blotting under constant darkness and shifted light/dark cycles\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — foundational identification paper, highly cited, multiple experimental approaches\",\n      \"pmids\": [\"9323128\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"PER1 protein exists in multiple tissue-specific isoforms (48 kDa nuclear form in brain, 55 kDa in kidney); a nuclear 48 kDa isoform follows a daily rhythm in mouse brain. Hypoxia increases PER1 protein levels and PER1 physically interacts with HIF-1α via co-immunoprecipitation, suggesting cross-talk between circadian and hypoxic PAS-domain pathways.\",\n      \"method\": \"Immunoblotting of nuclear/cytoplasmic fractions, co-immunoprecipitation, tissue fractionation\",\n      \"journal\": \"FASEB journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2/3 — co-IP plus subcellular fractionation in single study\",\n      \"pmids\": [\"11726537\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"Per1 mRNA amplitude in the pars tuberalis (PT) encodes photoperiodic time: the duration of the nocturnal melatonin signal is decoded as amplitude of Per1 (and ICER) gene expression in the PT, with short photoperiods greatly attenuating the peak.\",\n      \"method\": \"In situ hybridization of Per1 expression under long and short photoperiods in Syrian hamsters, manipulation of melatonin signal duration\",\n      \"journal\": \"PNAS\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — direct in vivo manipulation with quantitative expression readout, replicated across photoperiods\",\n      \"pmids\": [\"10449798\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"PER1 physically interacts with the androgen receptor (AR) and inhibits AR transactivation; forced expression of PER1 in LNCaP prostate cancer cells diminishes expression of androgen-sensitive genes and causes growth inhibition and apoptosis.\",\n      \"method\": \"Co-immunoprecipitation, reporter assays (transactivation), siRNA/overexpression with proliferation and apoptosis readouts\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2/3 — reciprocal functional assays plus co-IP in single lab\",\n      \"pmids\": [\"19752089\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"IRE1α endoribonuclease activity degrades PER1 mRNA post-transcriptionally in tumor cells without affecting PER1 gene transcription; inhibition of IRE1α prevents PER1 mRNA decay and reduces tumorigenesis.\",\n      \"method\": \"siRNA-mediated silencing, dominant-negative IRE1α strategy, qRT-PCR for mRNA vs. hnRNA, tumor growth assays\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1/2 — multiple orthogonal methods (DN mutant + siRNA + hnRNA assay) in single rigorous study\",\n      \"pmids\": [\"23752693\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Per1 and the mineralocorticoid receptor (MR) coordinately regulate αENaC transcription through E-box elements in the αENaC promoter; aldosterone increases Per1 occupancy on the αENaC E-box, and mutation of these E-boxes abolishes both basal and aldosterone-mediated promoter activity.\",\n      \"method\": \"Site-directed mutagenesis of E-boxes, DNA pull-down assays, chromatin immunoprecipitation (ChIP), reporter assays\",\n      \"journal\": \"Frontiers in physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — mutagenesis + ChIP + pull-down with functional reporter readout\",\n      \"pmids\": [\"24062694\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Per1 regulates expression of the endothelin axis genes (ET-1, ETA, ETB) in a tissue-specific and time-dependent manner in mouse kidney, lung, liver, and heart.\",\n      \"method\": \"Quantitative RT-PCR in Per1 heterozygous vs. wild-type mice tissues collected at rest and active phases\",\n      \"journal\": \"Life sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — clean genetic KO model with defined tissue-specific expression phenotype\",\n      \"pmids\": [\"24721511\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Per1 transcriptionally regulates NHE3 and SGLT1 (but not SGLT2) in renal proximal tubule cells; Per1 and CLOCK are detected at the NHE3 and SGLT1 promoters by ChIP, and pharmacological blockade of nuclear Per1 entry or siRNA knockdown decreases both mRNA and protein levels of NHE3 and SGLT1 and reduces Na⁺-K⁺-ATPase activity.\",\n      \"method\": \"ChIP, siRNA knockdown, pharmacological nuclear entry blockade, heterogeneous nuclear RNA analysis, protein immunoblotting\",\n      \"journal\": \"American journal of physiology. Renal physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1/2 — ChIP + siRNA + hnRNA + protein assays, multiple orthogonal approaches\",\n      \"pmids\": [\"26377793\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"EGR1 directly binds the proximal Per1 promoter to activate Per1 transcription; CLOCK/BMAL1 heterodimer transactivates Egr1 via a conserved E-box, placing EGR1 as an intermediate regulator of Per1 amplitude in the hepatic clock.\",\n      \"method\": \"Chromatin immunoprecipitation, luciferase reporter assays, Egr1-deficient mouse model with hepatic clock gene expression analysis\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1/2 — ChIP + reporter assay + in vivo KO model\",\n      \"pmids\": [\"26471974\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"The progesterone receptor (PR) directly binds the PER1 promoter to activate PER1 transcription during human endometrial decidualization; PER1 knockout attenuates decidual transformation by accelerating FOXO1 protein degradation.\",\n      \"method\": \"ChIP assay for PR at PER1 promoter, PER1 knockout in stromal cells, FOXO1 protein stability assays, qRT-PCR\",\n      \"journal\": \"The Journal of endocrinology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1/2 — ChIP + KO with defined cellular phenotype and downstream protein target\",\n      \"pmids\": [\"31518992\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"PER2 acts as a co-factor of CREB to facilitate formation of a transactivation complex (CREB/CRTC1/CBP) on the CRE element of the Per1 gene promoter in response to light or forskolin; absence of PER2 abolishes CBP-CREB interaction, reduces histone H3 acetylation, and decreases RNA Pol II recruitment to the Per1 gene.\",\n      \"method\": \"Co-immunoprecipitation, ChIP, in vitro and in vivo approaches with Per2 knockout, histone acetylation assays, RNA Pol II ChIP\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1/2 — multiple orthogonal methods (co-IP, ChIP, histone modification, KO) in single study\",\n      \"pmids\": [\"34741086\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"PER1 physically interacts with p53, reducing p53 stability and impairing its transcriptional activity; conversely, p53 represses PER1 transcription. PER1 overexpression reduces cancer cell sensitivity to drug-induced apoptosis in vitro and in vivo in xenograft models.\",\n      \"method\": \"Co-immunoprecipitation, reporter assays, overexpression/knockdown with apoptosis readouts, xenograft mouse model\",\n      \"journal\": \"International journal of molecular sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2/3 — co-IP + functional assays in single lab\",\n      \"pmids\": [\"33804124\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"PER1 forms a transcriptional complex with PPARγ to regulate circadian oscillation of HK2 expression; silencing PER1 disrupts the circadian rhythm of HK2-dependent glycolysis and reverses trastuzumab resistance in gastric cancer cells.\",\n      \"method\": \"Co-immunoprecipitation, siRNA knockdown, in vitro and in vivo glycolysis assays, chronotherapy experiments\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2/3 — co-IP + functional in vitro/in vivo assays in single lab\",\n      \"pmids\": [\"35255118\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"PER1 binds to HIF-1α protein to promote HIF-1α protein degradation (shown by co-immunoprecipitation and cycloheximide chase); HIF-1α in turn binds the PER1 promoter to feedback-inhibit PER1 transcription (shown by ChIP and dual luciferase assay), forming a PER1/HIF-1α negative feedback loop that promotes ferroptosis in oral squamous cell carcinoma.\",\n      \"method\": \"Co-immunoprecipitation, cycloheximide chase assay, ChIP, dual luciferase reporter assay, in vivo tumorigenicity assays\",\n      \"journal\": \"Translational oncology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1/2 — multiple orthogonal mechanistic methods (co-IP, CHX chase, ChIP, reporter) in single study\",\n      \"pmids\": [\"35134674\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"miR-34a directly targets PER1 mRNA to inhibit its expression; decreased miR-34a leads to increased Per1 levels that suppress cholangiocarcinoma cell proliferation and tumor growth; mRNA profiling shows Per1 overexpression regulates cell cycle, growth, and apoptosis pathways.\",\n      \"method\": \"Luciferase reporter assay for miRNA targeting, miR-34a inhibition/overexpression, cell proliferation and apoptosis assays, in vivo tumor growth, mRNA profiling\",\n      \"journal\": \"Journal of hepatology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — validated miRNA target + in vivo and in vitro functional assays\",\n      \"pmids\": [\"26923637\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"LncRNA TPTEP1 sponges miR-548d-3p to derepress KLF9, which binds the PER1 promoter to activate PER1 transcription, thereby inhibiting gastric cancer cell migration and invasion.\",\n      \"method\": \"Luciferase assay for sponge activity and 3'UTR targeting, ChIP for KLF9 binding to PER1 promoter, wound healing and transwell assays, nude mouse xenograft\",\n      \"journal\": \"Pathology, research and practice\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2/3 — ChIP + luciferase + functional cellular assays\",\n      \"pmids\": [\"35985238\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Per1/Per2 double knockout in mice reduces testosterone synthesis by downregulating steroidogenic enzymes (Cyp11a1, Cyp17a1, Hsd17b3, Hsd3b1, StAR) via impaired PKA-CREB-StAR signaling, leading to decreased sperm motility and reduced fertility in elderly males.\",\n      \"method\": \"Per1/Per2 double knockout mouse model, hormone-targeted metabolomics, transcriptomic analysis, Western blotting for StAR, p-CREB, PKA, AC1\",\n      \"journal\": \"International journal of molecular sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic KO with defined mechanistic pathway (PKA-StAR) and multiple molecular readouts\",\n      \"pmids\": [\"35806403\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Local knockdown of Per1 within the dorsal hippocampus impairs spatial memory consolidation without affecting circadian rhythm or sleep, demonstrating a local, circuit-level role for Per1 in hippocampal memory independent of its SCN circadian function.\",\n      \"method\": \"Lentiviral Per1 knockdown in dorsal hippocampus, Object Location Memory behavioral testing, RNA-sequencing for identification of Per1 as learning-induced oscillator\",\n      \"journal\": \"Neuropsychopharmacology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — targeted in vivo knockdown with specific behavioral phenotype and transcriptomic identification\",\n      \"pmids\": [\"37264172\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"In the SCN, PER1-expressing neurons are differentially distributed from PER2-expressing neurons across the rostro-caudal extent, with high PER1 expression concentrated in a broad central area and high PER2 in rostral and caudal portions, suggesting spatially distinct functional roles in circadian timekeeping.\",\n      \"method\": \"Triple immunofluorescence labeling and automated image analysis of PER1, PER2, and gastrin-releasing peptide in sagittal SCN sections\",\n      \"journal\": \"The European journal of neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct quantitative protein localization across defined anatomical regions\",\n      \"pmids\": [\"27740710\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Estradiol and progesterone upregulate Per1 expression in specific compartments of the rat uterus (LE, GE, M for estradiol; LE, GE, S for progesterone); effects are blocked by the respective receptor antagonists ICI182780 and RU486, demonstrating steroid hormone regulation of Per1 expression.\",\n      \"method\": \"In situ hybridization, immunofluorescence, RT-PCR in ovariectomized rats and cultured uterine stromal cells with hormone/antagonist treatment\",\n      \"journal\": \"The Journal of endocrinology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — in vivo and in vitro evidence with receptor antagonist validation\",\n      \"pmids\": [\"17761890\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"PER1 is a bHLH/PAS-domain circadian clock protein that functions as a transcriptional regulator and co-factor within the core negative feedback loop: it is transcriptionally activated by CLOCK/BMAL1 via E-boxes (with intermediaries including EGR1, PR, and CREB/CRTC1/CBP complexes), repressed post-transcriptionally by IRE1α-mediated mRNA decay, and its protein interacts with HIF-1α (promoting HIF-1α degradation), the androgen receptor (inhibiting AR transactivation), p53 (reducing p53 stability), and PPARγ (co-regulating metabolic gene oscillation), while also co-occupying gene promoters with MR and CLOCK to drive circadian transcription of sodium transport genes (αENaC, NHE3, SGLT1) in the kidney, and independently regulating hippocampal memory consolidation at the local circuit level.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"PER1 is a core component of the mammalian circadian clock that functions both as a transcriptional co-regulator within the negative feedback loop and as a versatile protein–protein interaction hub linking circadian timing to metabolism, hormone signaling, hypoxia, and tumor suppression. Identified as the mammalian ortholog of Drosophila period, PER1 is rhythmically expressed in the suprachiasmatic nucleus and peripheral tissues, is transcriptionally activated by CLOCK/BMAL1 via E-box elements and additional regulators including EGR1, progesterone receptor, and the PER2-dependent CREB/CRTC1/CBP complex, and is post-transcriptionally regulated by IRE1α-mediated mRNA decay and miR-34a targeting [PMID:9323128, PMID:24062694, PMID:26471974, PMID:31518992, PMID:34741086, PMID:23752693, PMID:26923637]. At the effector level, PER1 occupies E-box-containing promoters together with CLOCK to drive circadian transcription of renal sodium transport genes (αENaC, NHE3, SGLT1), forms complexes with PPARγ to regulate glycolytic gene oscillation, promotes HIF-1α protein degradation, inhibits androgen receptor transactivation, and reduces p53 stability, thereby influencing cell proliferation, apoptosis, ferroptosis, and drug resistance [PMID:26377793, PMID:35255118, PMID:35134674, PMID:19752089, PMID:33804124]. Beyond its canonical circadian role, local Per1 expression in the dorsal hippocampus is required for spatial memory consolidation independent of SCN-driven rhythms [PMID:37264172].\",\n  \"teleology\": [\n    {\n      \"year\": 1997,\n      \"claim\": \"The identification of PER1 (RIGUI) as a bHLH/PAS-domain mammalian ortholog of Drosophila period, with circadian expression in the SCN persisting in constant darkness, established for the first time that mammals possess a molecular clock gene homologous to invertebrate period.\",\n      \"evidence\": \"Molecular cloning, sequence homology, in situ hybridization and Northern blotting under constant darkness and shifted LD cycles in mouse SCN\",\n      \"pmids\": [\"9323128\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No loss-of-function data to confirm requirement for circadian rhythmicity\", \"Protein-level rhythmicity not demonstrated\", \"No mechanistic insight into how PER1 feeds back on the clock\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Demonstrating that Per1 mRNA amplitude in the pars tuberalis encodes photoperiodic time established PER1 as a decoder of melatonin signal duration, extending its role from circadian oscillator to seasonal timer.\",\n      \"evidence\": \"In situ hybridization of Per1 in Syrian hamster pars tuberalis under long vs. short photoperiods with melatonin signal manipulation\",\n      \"pmids\": [\"10449798\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism by which melatonin controls Per1 transcription in PT not defined\", \"Downstream effectors of Per1 amplitude in seasonal physiology unknown\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Discovery of tissue-specific PER1 isoforms and its physical interaction with HIF-1α revealed cross-talk between circadian PAS-domain proteins and the hypoxia response, though functional consequences were unclear.\",\n      \"evidence\": \"Immunoblotting of nuclear/cytoplasmic fractions across tissues, co-immunoprecipitation of PER1 and HIF-1α\",\n      \"pmids\": [\"11726537\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Only forward co-IP shown; reciprocal validation absent in original study\", \"Functional impact of PER1–HIF-1α interaction on either pathway not demonstrated\", \"Isoform-specific functions unresolved\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Showing that estradiol and progesterone regulate Per1 expression in distinct uterine compartments via their cognate receptors established hormonal control of Per1 as a mechanism coupling reproductive steroid signaling to local peripheral clocks.\",\n      \"evidence\": \"In situ hybridization and RT-PCR in ovariectomized rats with receptor antagonist (ICI182780, RU486) blockade\",\n      \"pmids\": [\"17761890\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether steroid hormones directly bind the Per1 promoter or act indirectly was not resolved\", \"Functional consequence of Per1 induction for uterine physiology not tested\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"PER1's physical interaction with the androgen receptor and inhibition of AR transactivation, causing growth arrest and apoptosis in prostate cancer cells, revealed a direct molecular link between the circadian clock protein and hormone-dependent cancer.\",\n      \"evidence\": \"Co-IP of PER1–AR, reporter assays for AR transactivation, siRNA/overexpression with proliferation and apoptosis readouts in LNCaP cells\",\n      \"pmids\": [\"19752089\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Domain mapping of PER1–AR interaction not performed\", \"Mechanism of growth inhibition downstream of AR repression not delineated\", \"In vivo confirmation with genetic models absent\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Two parallel discoveries established PER1 as an output transcription factor of the renal clock and as a target of IRE1α-mediated post-transcriptional regulation: PER1 and MR co-regulate αENaC transcription via E-box elements, while IRE1α endonuclease degrades PER1 mRNA post-transcriptionally in tumor cells, providing a mechanism for circadian disruption in cancer.\",\n      \"evidence\": \"ChIP, E-box mutagenesis, and reporter assays for αENaC regulation; siRNA, dominant-negative IRE1α, and hnRNA assays for post-transcriptional decay\",\n      \"pmids\": [\"24062694\", \"23752693\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether IRE1α cleaves PER1 mRNA directly or via an intermediate is unresolved\", \"αENaC regulation not tested in Per1-null animals\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Extension of PER1's renal transcriptional targets to NHE3 and SGLT1 — with ChIP confirming PER1 and CLOCK co-occupancy at these promoters — consolidated PER1 as a direct circadian transcriptional regulator of renal sodium transport, and EGR1 was identified as an intermediate transcription factor linking CLOCK/BMAL1 to Per1 promoter activation.\",\n      \"evidence\": \"ChIP, siRNA, pharmacological nuclear entry blockade, hnRNA analysis for renal targets; ChIP, reporter assays, and Egr1-KO mice for EGR1–Per1 axis\",\n      \"pmids\": [\"26377793\", \"26471974\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether EGR1-mediated Per1 regulation occurs in non-hepatic tissues unknown\", \"Relative contribution of E-box vs. EGR1-binding site to Per1 amplitude not quantified\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Identification of PER1 as a direct target of miR-34a added a microRNA layer to post-transcriptional clock control and showed that Per1 overexpression suppresses cholangiocarcinoma growth, reinforcing its tumor-suppressive function.\",\n      \"evidence\": \"Luciferase reporter assay for 3′UTR targeting, miR-34a modulation with in vivo tumor xenograft readouts\",\n      \"pmids\": [\"26923637\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether miR-34a regulation of PER1 is circadian phase-dependent not tested\", \"Downstream effectors of PER1-mediated growth suppression in cholangiocarcinoma uncharacterized\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Progesterone receptor directly binds the PER1 promoter to activate its transcription during endometrial decidualization, and PER1 knockout impairs decidualization by destabilizing FOXO1, revealing a specific reproductive function downstream of PER1.\",\n      \"evidence\": \"ChIP for PR at PER1 promoter, PER1 knockout in stromal cells with FOXO1 protein stability and decidualization assays\",\n      \"pmids\": [\"31518992\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether FOXO1 stabilization is a direct PER1 protein interaction or transcriptional effect not resolved\", \"Relevance to in vivo fertility phenotypes not demonstrated\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Two studies deepened PER1's role in transcription factor regulation: PER2 was shown to scaffold CREB/CRTC1/CBP assembly at the Per1 CRE element for light-induced Per1 transcription, and PER1 was found to physically interact with p53, reducing its stability and transcriptional activity, with functional consequences for drug-induced apoptosis.\",\n      \"evidence\": \"Co-IP, ChIP, histone acetylation, and RNA Pol II ChIP in Per2-KO SCN tissue; co-IP, reporter assays, overexpression/knockdown with xenograft models for PER1–p53\",\n      \"pmids\": [\"34741086\", \"33804124\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether PER1 promotes p53 degradation via ubiquitin-proteasome pathway not established\", \"Domain requirements for PER1–p53 interaction unknown\", \"PER2-mediated Per1 induction mechanism not shown to be conserved in peripheral tissues\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"A cluster of 2022 studies established PER1 as (i) a PPARγ co-factor driving circadian HK2 oscillation and glycolytic drug resistance, (ii) a direct promoter of HIF-1α degradation forming a reciprocal negative feedback loop that controls ferroptosis, (iii) a target of KLF9-mediated transcriptional activation via a lncRNA sponge pathway in gastric cancer, and (iv) a regulator of testosterone biosynthesis through the PKA-CREB-StAR axis.\",\n      \"evidence\": \"Co-IP, siRNA, glycolysis assays, chronotherapy experiments for PPARγ–PER1; co-IP, CHX chase, ChIP, dual luciferase for PER1–HIF-1α loop; ChIP for KLF9 at PER1 promoter and xenograft assays; Per1/Per2 double-KO mice with hormone metabolomics and PKA-StAR pathway analysis\",\n      \"pmids\": [\"35255118\", \"35134674\", \"35985238\", \"35806403\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"PPARγ–PER1 complex composition and DNA-binding mode unresolved\", \"Whether PER1 recruits a specific E3 ligase for HIF-1α degradation is unknown\", \"Per1 vs. Per2 individual contributions to steroidogenesis not separated in double-KO\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Local knockdown of Per1 in dorsal hippocampus impaired spatial memory consolidation without affecting circadian rhythm or sleep, establishing a non-canonical, circuit-level function for PER1 outside the SCN clock network.\",\n      \"evidence\": \"Lentiviral Per1 knockdown in dorsal hippocampus with Object Location Memory testing and RNA-seq\",\n      \"pmids\": [\"37264172\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular targets of PER1 in hippocampal memory consolidation not identified\", \"Whether other Period genes compensate or share this function unknown\", \"Electrophysiological correlates of Per1-dependent memory consolidation not explored\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key unresolved questions include: the structural basis of PER1's interaction with its diverse protein partners (AR, HIF-1α, p53, PPARγ), whether PER1 recruits specific ubiquitin ligases for target degradation, how tissue-specific isoforms (48 vs. 55 kDa) differ functionally, and the full scope of PER1's non-circadian roles in memory and reproduction.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No crystal or cryo-EM structure of PER1 in complex with any partner\", \"Isoform-specific functions remain entirely uncharacterized\", \"No genome-wide PER1 ChIP-seq in peripheral tissues to define direct target gene repertoire\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140110\", \"supporting_discovery_ids\": [5, 7, 9, 12, 13]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [3, 11, 13]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [1, 5, 7]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [1]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-9909396\", \"supporting_discovery_ids\": [0, 2, 5, 7, 8, 10, 18]},\n      {\"term_id\": \"R-HSA-74160\", \"supporting_discovery_ids\": [5, 7, 8, 9, 12, 13]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [3, 11, 13, 19]},\n      {\"term_id\": \"R-HSA-382551\", \"supporting_discovery_ids\": [5, 7]},\n      {\"term_id\": \"R-HSA-1474165\", \"supporting_discovery_ids\": [9, 16]}\n    ],\n    \"complexes\": [\n      \"PER1–CLOCK transcriptional complex\",\n      \"PER1–PPARγ transcriptional complex\"\n    ],\n    \"partners\": [\n      \"CLOCK\",\n      \"HIF1A\",\n      \"AR\",\n      \"TP53\",\n      \"PPARG\",\n      \"NR3C2\",\n      \"EGR1\",\n      \"PGR\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}