{"gene":"MSL1","run_date":"2026-06-10T02:59:51","timeline":{"discoveries":[{"year":1993,"finding":"MSL1 protein associates with hundreds of sites along the length of the X chromosome in male (but not female) nuclei, consistent with a direct role in increasing X-linked gene transcription in males.","method":"Immunostaining/chromosome localization assay","journal":"Genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct localization experiment with sex-specific functional context, single lab","pmids":["8325488"],"is_preprint":false},{"year":1994,"finding":"X-chromosomal association of MSL-1 depends on wild-type function of the other MSL proteins (MLE, MSL-2, MSL-3), indicating MSL-1 participates in a multi-subunit complex; binding is negatively regulated by the master sex-determination gene Sxl.","method":"Genetic analysis; immunostaining in mutant backgrounds","journal":"The EMBO journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis with direct localization readout, single lab","pmids":["8062831"],"is_preprint":false},{"year":1995,"finding":"MSL-1, MSL-2, MLE, and histone H4Ac16 are mutually interdependent for sub-nuclear (X chromosome) localization from early embryogenesis; loss of any one MSL protein abolishes co-localization of the others.","method":"Immunostaining of embryos in msl mutant backgrounds","journal":"Mechanisms of development","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis with direct localization readout, single lab","pmids":["8562424"],"is_preprint":false},{"year":1997,"finding":"MSL-2 binding to the X chromosome depends on MSL-1; the two proteins co-localize precisely, suggesting they function together to associate with the X. The MSL-2 RING finger domain is essential for MSL-2 function in this complex.","method":"Immunostaining in msl mutant backgrounds; EMS suppressor screen; site-directed mutagenesis of MSL-2","journal":"Genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis plus direct localization, single lab","pmids":["9409833"],"is_preprint":false},{"year":1998,"finding":"MSL1 protein abundance in females is reduced compared to males through two mechanisms: predominantly post-translational protein instability and secondarily reduced protein synthesis. Overcoming both controls by co-overexpressing MSL1 and MSL2 in females causes 100% female-specific lethality.","method":"Western blot quantification; overexpression genetics in Drosophila","journal":"Genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — biochemical quantification plus genetic functional readout, single lab","pmids":["9755201"],"is_preprint":false},{"year":2000,"finding":"MSL1 serves as a scaffold for MSL complex assembly: its N-terminal domain interacts with MSL2, and its C-terminal domain co-purifies with both MSL3 and MOF (histone acetyltransferase). Dominant-negative overexpression of either domain causes male-specific lethality, and the C-terminal domain shows similarity to the transcription co-activator CBP.","method":"FLAG affinity purification; GST pulldown; co-immunoprecipitation with HA-tagged MSL3; dominant-negative overexpression genetics","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal binding assays (FLAG pulldown, GST pulldown, co-IP) plus genetic dominant-negative phenotype, independently consistent with structural data","pmids":["10619853"],"is_preprint":false},{"year":2005,"finding":"The N-terminal region of Drosophila MSL1 contains three functionally distinct motifs: (1) a basic motif required for binding to ~30 high-affinity X-chromosomal sites; (2) a glycine-rich motif mediating MSL1 self-association in vitro and binding to the assembled MSL complex; (3) a leucine zipper-like motif that binds MSL2 and is required for X chromosome association.","method":"In vitro self-association assay; co-immunoprecipitation; immunostaining of transgenic flies expressing N-terminal domain fragments; site-directed mutagenesis","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — in vitro binding assays plus mutagenesis plus in vivo localization, multiple orthogonal methods, single lab","pmids":["16199870"],"is_preprint":false},{"year":2006,"finding":"ChIP-chip analysis reveals MSL-1 binding profile across the male X chromosome; MSL-1 binding does not strictly correlate with transcriptional output of target genes, suggesting additional factors determine dosage-compensated status beyond direct MSL-1 binding.","method":"Chromatin immunoprecipitation coupled with DNA microarray (ChIP-chip)","journal":"Genes & development","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genome-wide ChIP-chip with functional interpretation, single lab","pmids":["16547175"],"is_preprint":false},{"year":2007,"finding":"Incorporation of roX noncoding RNAs into the MSL complex alters its chromatin-binding specificity. The amino-terminal RING finger domain of MSL2, acting as a complex with MSL1, mediates binding to the heterochromatic chromocenter and a few chromosomal arm sites; this requires the same basic motif of MSL1 needed for high-affinity X-chromosomal binding.","method":"Transgenic expression of MSL2 domain fragments; immunostaining; co-immunoprecipitation","journal":"Molecular and cellular biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — domain dissection with localization and binding assays, single lab","pmids":["18086881"],"is_preprint":false},{"year":2007,"finding":"Mammalian MSL1 (hampin) interacts with MYST1/MOF, TTC4, KIAA0103, NOP17, and transcription factor GCBP as identified by yeast two-hybrid; the majority of interactions were confirmed by in vitro pulldown of bacterially expressed proteins.","method":"Yeast two-hybrid screen; in vitro pulldown assay","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — yeast two-hybrid confirmed by pulldown, multiple interactors, single lab","pmids":["17335777"],"is_preprint":false},{"year":2011,"finding":"Crystal structures of mammalian MSL1 binary complexes with MSL3 and MOF reveal: MSL1 interacts with MSL3 as an extended chain forming an extensive hydrophobic interface; the MSL1-MOF interface involves electrostatic interactions between the MOF HAT domain and a long helix of MSL1. Selective disruption of Msl1-Msl3 or Msl1-Mof interactions in Drosophila severely impairs MSL complex targeting to gene bodies and high-affinity sites without affecting promoter binding.","method":"X-ray crystallography; structure-based mutagenesis; ChIP in Drosophila","journal":"Nature structural & molecular biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structures with functional validation by mutagenesis and ChIP, multiple orthogonal methods","pmids":["21217699"],"is_preprint":false},{"year":2012,"finding":"Crystal structure of the MSL1/MSL2 core shows two MSL2 subunits binding to an MSL1 dimer; MSL1 dimerization is MSL2-independent, but MSL2 can only interact with the MSL1 dimer. Structure-based mutants show Msl1 dimerization is essential for MSL complex targeting to and spreading along X-linked gene bodies. Additionally, MSL1 is a substrate for MSL2 E3 ubiquitin ligase activity. MSL1 binding to promoters is independent of its dimerization status and other MSL proteins.","method":"X-ray crystallography; structure-based mutagenesis; ChIP; in vitro ubiquitylation assay","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure with mutagenesis, in vitro enzymatic assay, and ChIP validation, multiple orthogonal methods","pmids":["23084835"],"is_preprint":false},{"year":2013,"finding":"Human MSL1 and Nupr1 are recruited to the nucleus in response to DNA damage and form a complex essential for cell survival under cisplatin treatment. MSL1 binds Nupr1 with moderate affinity (Kd ~2.8 µM) in an entropically driven process. MSL1 does not bind undamaged DNA but binds chemically damaged DNA with moderate affinity (~1.2 µM).","method":"Biophysical binding assays (ITC, fluorescence); NMR; cell viability assays; nuclear co-localization","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple biophysical methods (ITC, NMR, fluorescence) establishing binding affinities, single lab","pmids":["24205110"],"is_preprint":false},{"year":2014,"finding":"Mammalian MSL1 contains two distinct nuclear localization signals (NLS): a novel NLS common to all isoforms, and a previously known bipartite NLS in the PEHE domain. Isoforms possessing both NLS localize to sub-nuclear foci and can direct co-chaperone TTC4 there; all isoforms retain the ability to affect H4K16 acetylation.","method":"Subcellular localization of MSL1 isoforms; NLS deletion constructs; co-localization with TTC4; H4K16 acetylation assay","journal":"Journal of cellular biochemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct localization experiments with functional consequence (H4K16ac), single lab","pmids":["24913909"],"is_preprint":false},{"year":2016,"finding":"MSL1 interacts functionally with CDK7 (a subunit of the CAK complex of TFIIH); MSL1 depletion leads to decreased Ser5 phosphorylation of RNA polymerase II. MSL1 is itself a phosphoprotein, and transgenic flies expressing MSL1 phosphomutants show mislocalization of MOF and reduced H4K16 acetylation, causing male lethality.","method":"Genetic interaction; biochemical interaction assays; phospho-Pol II ChIP; transgenic phosphomutant Drosophila","journal":"Nature structural & molecular biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic and biochemical epistasis with multiple functional readouts (Pol II Ser5 phosphorylation, MOF localization, H4K16ac, male lethality), replicated across two Drosophila species","pmids":["27183194"],"is_preprint":false},{"year":2019,"finding":"Purified MSL1/MSL2 complex ubiquitylates histone H2B (at K34) in vitro in a substrate-configuration-dependent manner; MSL1/2 efficiently ubiquitylates free histone substrates but very poorly modifies intact nucleosomes, implying a requirement for nucleosome structural alteration for efficient H2BK34 ubiquitylation.","method":"In vitro ubiquitylation assay with purified proteins; nucleosome gel-mobility shift assay","journal":"Archives of biochemistry and biophysics","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — in vitro reconstituted enzymatic assay, single lab, single study","pmids":["30930284"],"is_preprint":false},{"year":2021,"finding":"PBK kinase phosphorylates MSL1 and enhances MSL1 interaction with MSL2, MSL3, and KAT8 (components of the MSL complex). This promotes MSL complex enrichment on the CD276 promoter, leading to increased H4K16 acetylation and CD276 transcriptional activation in nasopharyngeal carcinoma cells.","method":"Co-immunoprecipitation; ChIP; phosphorylation assay; knockdown/overexpression in cancer cells; H4K16ac western blot","journal":"Oncogenesis","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP and ChIP with functional readout, single lab, multiple methods","pmids":["33431797"],"is_preprint":false},{"year":2021,"finding":"Phosphorylation-site mutations in Drosophila MSL1 (replacing phosphorylatable residues) do not affect specific binding of the dosage compensation complex to the male X chromosome or its functional activity, indicating these particular phosphorylation sites are dispensable for dosage compensation.","method":"Transgenic Drosophila expressing MSL1 phosphomutants; immunostaining","journal":"Doklady. Biochemistry and biophysics","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — direct in vivo negative result with transgenic mutants, single lab","pmids":["34426916"],"is_preprint":false},{"year":2023,"finding":"MSL1 forms liquid-liquid phase separation condensates with STAT3 or histone H4 in hepatocytes, enriching acetyl-CoA (Ac-CoA) in these condensates. Ac-CoA in turn enhances MSL1 condensate formation, synergistically promoting acetylation of STAT3 K685 and H4K16, thereby stimulating liver regeneration after partial hepatectomy.","method":"Phase separation assays; co-immunoprecipitation; acetylation assays; partial hepatectomy mouse model; MSL1 knockdown/overexpression","journal":"Advanced science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — phase separation assays with functional in vivo readout, single lab","pmids":["37279389"],"is_preprint":false},{"year":2024,"finding":"The N-terminal region of Drosophila MSL1 (amino acids 3–7) is critical for interaction with roX2 RNA and for MSL complex binding to high-affinity sites (HAS) on the X chromosome. MSL1GS (N-terminal substitution mutant) binds promoters like wild-type MSL1 but fails to co-bind MSL2 and MSL3 at HAS; overexpression of MSL2 partially restores dosage compensation, indicating roX RNA interaction with MSL1 N-terminus is essential for efficient MSL complex assembly at HAS.","method":"Transgenic Drosophila expressing MSL1 deletion/substitution mutants; ChIP; immunostaining; RNA immunoprecipitation","journal":"eLife","confidence":"High","confidence_rationale":"Tier 2 / Moderate — structure-function dissection with multiple orthogonal methods (ChIP, immunostaining, RIP, genetics), rigorous in vivo validation","pmids":["39699942"],"is_preprint":false},{"year":2025,"finding":"MSL1 negatively regulates KCTD12 expression in colon cancer cells; Erastin-induced ferroptosis suppresses MSL1 expression leading to KCTD12 upregulation, which in turn reduces SLC7A11 levels, promoting ferroptosis through altered ROS, GSH, and MDA levels.","method":"Knockdown/overexpression studies; biochemical assays for ROS, GSH, MDA; ferroptosis cell death assay","journal":"Cell death & disease","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, knockdown/overexpression without direct molecular mechanism between MSL1 and KCTD12","pmids":["40221412"],"is_preprint":false}],"current_model":"MSL1 functions as the central scaffold protein of the MSL histone acetyltransferase complex: its N-terminal basic motif mediates DNA/roX RNA binding and X-chromosome high-affinity site recognition, a glycine-rich motif mediates MSL1 self-dimerization (essential for complex spreading along the X), and leucine zipper-like and C-terminal (PEHE) domains recruit MSL2, MSL3, and the acetyltransferase KAT8/MOF respectively, as established by crystal structures and mutagenesis; MSL1 dimerization is required for MSL2 engagement and X-chromosomal spreading; MSL1 also interacts with CDK7/TFIIH to promote RNA Pol II Ser5 phosphorylation and is itself regulated by phosphorylation (by PBK) and ubiquitylation (by MSL2 E3 ligase), while in mammals it additionally forms phase-separation condensates to facilitate H4K16 and STAT3 acetylation."},"narrative":{"mechanistic_narrative":"MSL1 is the central scaffold of the MSL histone acetyltransferase complex that drives X-chromosome dosage compensation in male Drosophila, decorating hundreds of X-linked sites in a sex-specific manner and acting interdependently with MSL2, MSL3, MLE and H4K16 acetylation [PMID:8325488, PMID:8562424, PMID:10619853]. As a scaffold, MSL1 uses spatially distinct regions: an N-terminal basic motif that recognizes ~30 high-affinity X-chromosomal sites and engages roX noncoding RNA, a glycine-rich motif that mediates MSL1 self-association, and a leucine-zipper-like motif that binds MSL2, while its C-terminal region co-purifies with MSL3 and the acetyltransferase MOF/KAT8 [PMID:10619853, PMID:16199870, PMID:39699942]. Crystal structures define these interfaces and show that MSL2 binds only an MSL1 dimer, with MSL1 dimerization being essential for complex targeting to and spreading along X-linked gene bodies, whereas promoter binding is dimerization- and partner-independent [PMID:21217699, PMID:23084835]. The MSL1/MSL2 module also carries MSL2-dependent enzymatic outputs: MSL1 is a substrate for MSL2 E3 ubiquitin ligase activity, and the purified MSL1/MSL2 complex ubiquitylates histone H2B at K34 on free histone substrates [PMID:23084835, PMID:30930284]. MSL1 couples chromatin modification to transcription by interacting with CDK7/TFIIH to promote RNA Pol II Ser5 phosphorylation, and its own phosphorylation state controls MOF localization and H4K16 acetylation [PMID:27183194]. In mammals MSL1 retains MOF binding and H4K16-acetylation activity, localizes to sub-nuclear foci via two NLS, and forms liquid-liquid phase-separation condensates with STAT3 or histone H4 that concentrate acetyl-CoA to promote STAT3 K685 and H4K16 acetylation during liver regeneration [PMID:17335777, PMID:24913909, PMID:37279389]. MSL1 is additionally recruited to the nucleus upon DNA damage where it binds damaged DNA and Nupr1 to support cell survival [PMID:24205110].","teleology":[{"year":1993,"claim":"Established that MSL1 is a chromatin-associated factor acting specifically in males, linking it to X-linked transcriptional upregulation.","evidence":"Sex-specific immunostaining of MSL1 along the X chromosome in Drosophila nuclei","pmids":["8325488"],"confidence":"Medium","gaps":["Did not define molecular partners or mechanism of X recognition","No biochemical demonstration of a complex"]},{"year":1995,"claim":"Showed MSL1 functions within a mutually dependent multi-subunit assembly, not as an isolated factor, by demonstrating reciprocal localization requirements with MSL2, MSL3, MLE and H4K16ac.","evidence":"Immunostaining in msl mutant backgrounds across embryogenesis","pmids":["8062831","8562424","9409833"],"confidence":"Medium","gaps":["Interdependence was genetic/localization-based, not direct biochemical contact mapping","Order of assembly unresolved"]},{"year":1998,"claim":"Defined how MSL1 dosage is restricted to males, identifying post-translational instability and reduced synthesis as the controls preventing female complex assembly.","evidence":"Western quantification and co-overexpression genetics in Drosophila","pmids":["9755201"],"confidence":"Medium","gaps":["Molecular machinery of female-specific instability not identified","Did not link to ubiquitylation directly"]},{"year":2000,"claim":"Established MSL1 as the scaffold by mapping an N-terminal MSL2-binding region and a C-terminal region that co-purifies with MSL3 and MOF, giving the complex a modular architecture.","evidence":"FLAG/GST pulldowns, co-IP, and dominant-negative domain overexpression in Drosophila","pmids":["10619853"],"confidence":"High","gaps":["Domain boundaries were coarse without structural detail","Stoichiometry not defined"]},{"year":2005,"claim":"Resolved the N-terminus into three functional motifs, separating high-affinity-site DNA binding, self-association, and MSL2 binding.","evidence":"In vitro self-association, co-IP, and transgenic localization of N-terminal fragments with mutagenesis","pmids":["16199870"],"confidence":"High","gaps":["Did not establish how self-association couples to spreading at atomic resolution"]},{"year":2007,"claim":"Defined the chromatin-binding behavior and partner repertoire, showing MSL-1 binding does not strictly predict transcriptional output and identifying mammalian MSL1 interactors including MOF and TTC4.","evidence":"ChIP-chip on the male X; yeast two-hybrid with in vitro pulldown confirmation","pmids":["16547175","17335777"],"confidence":"Medium","gaps":["Additional determinants of dosage-compensated status not identified","Functional relevance of several Y2H interactors untested"]},{"year":2012,"claim":"Provided structural mechanism: MSL1 dimerizes independently of MSL2, MSL2 binds only the dimer, and dimerization is required for targeting and spreading along gene bodies but not promoter binding; also identified MSL1 as an MSL2 ubiquitylation substrate.","evidence":"X-ray crystallography of MSL1/MSL2 and MSL1/MSL3 and MSL1/MOF interfaces, structure-based mutagenesis, ChIP, in vitro ubiquitylation","pmids":["21217699","23084835"],"confidence":"High","gaps":["Functional consequence of MSL1 ubiquitylation in vivo unresolved","How dimerization drives spreading mechanistically not fully defined"]},{"year":2013,"claim":"Extended MSL1 function into the DNA-damage response, showing it binds damaged DNA and Nupr1 to support survival under genotoxic stress.","evidence":"ITC, NMR, fluorescence binding, nuclear co-localization and cell viability under cisplatin","pmids":["24205110"],"confidence":"Medium","gaps":["Link to the canonical MSL acetyltransferase function unclear","Downstream repair pathway not defined"]},{"year":2016,"claim":"Connected MSL1 to transcriptional machinery and its own regulation, showing it engages CDK7/TFIIH to promote Pol II Ser5 phosphorylation and that MSL1 phosphorylation controls MOF localization and H4K16ac.","evidence":"Genetic/biochemical interaction, phospho-Pol II ChIP, transgenic phosphomutant Drosophila across two species","pmids":["27183194"],"confidence":"High","gaps":["Kinase responsible in vivo not pinned down in this study","Direct CDK7 contact interface unmapped"]},{"year":2019,"claim":"Demonstrated an intrinsic enzymatic output of the MSL1/MSL2 module, ubiquitylating H2BK34 with strong dependence on substrate configuration.","evidence":"In vitro ubiquitylation with purified proteins and nucleosome gel-shift","pmids":["30930284"],"confidence":"Medium","gaps":["Poor activity on intact nucleosomes leaves physiological substrate unclear","Single in vitro study"]},{"year":2021,"claim":"Identified PBK as a kinase that phosphorylates MSL1 to enhance complex assembly and target-gene activation, while a separate Drosophila study showed certain phosphosites are dispensable for dosage compensation.","evidence":"Co-IP/ChIP/phosphorylation assays in carcinoma cells; transgenic phosphomutant immunostaining in Drosophila","pmids":["33431797","34426916"],"confidence":"Medium","gaps":["Which specific MSL1 residues mediate context-dependent effects not reconciled across systems","Generality of PBK regulation beyond cancer cells untested"]},{"year":2023,"claim":"Revealed a phase-separation mechanism in mammals, with MSL1 condensates concentrating acetyl-CoA to promote STAT3 and H4K16 acetylation during liver regeneration.","evidence":"Phase separation and acetylation assays, co-IP, partial hepatectomy mouse model","pmids":["37279389"],"confidence":"Medium","gaps":["Condensate composition relative to canonical MSL complex undefined","Sequence determinants of MSL1 phase separation unmapped"]},{"year":2024,"claim":"Established that the extreme MSL1 N-terminus mediates roX2 RNA binding required for complex co-binding at high-affinity sites, distinguishing RNA-dependent HAS recruitment from RNA-independent promoter binding.","evidence":"Transgenic MSL1 substitution mutants with ChIP, immunostaining, and RNA immunoprecipitation","pmids":["39699942"],"confidence":"High","gaps":["Structural basis of MSL1 N-terminus/roX2 contact not determined","How RNA binding integrates with dimerization-driven spreading unresolved"]},{"year":2025,"claim":"Proposed an MSL1 role in ferroptosis via negative regulation of KCTD12 and the SLC7A11 axis in colon cancer.","evidence":"Knockdown/overexpression with ROS, GSH, MDA and ferroptosis assays","pmids":["40221412"],"confidence":"Low","gaps":["No direct molecular mechanism linking MSL1 to KCTD12 established","Single lab, indirect readouts only"]},{"year":null,"claim":"How the canonical MSL acetyltransferase scaffold function integrates with the mammalian-specific activities (DNA-damage response, phase separation, ferroptosis regulation) into a unified model remains unresolved.","evidence":"","pmids":[],"confidence":"Low","gaps":["No structural model of the full mammalian complex with RNA","Physiological H2BK34 ubiquitylation context undefined","Mechanistic link between condensate formation and chromatin targeting unknown"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[5,6,10,11]},{"term_id":"GO:0003723","term_label":"RNA binding","supporting_discovery_ids":[8,19]},{"term_id":"GO:0003677","term_label":"DNA binding","supporting_discovery_ids":[6,12]},{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[11,15]}],"localization":[{"term_id":"GO:0000228","term_label":"nuclear chromosome","supporting_discovery_ids":[0,2,7]},{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[12,13]}],"pathway":[{"term_id":"R-HSA-4839726","term_label":"Chromatin organization","supporting_discovery_ids":[5,10,14]},{"term_id":"R-HSA-74160","term_label":"Gene expression (Transcription)","supporting_discovery_ids":[0,14,16]}],"complexes":["MSL complex"],"partners":["MSL2","MSL3","KAT8/MOF","MLE","CDK7","STAT3","NUPR1","PBK"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q68DK7","full_name":"Male-specific lethal 1 homolog","aliases":["Male-specific lethal 1-like 1","MSL1-like 1","Male-specific lethal-1 homolog 1"],"length_aa":614,"mass_kda":67.1,"function":"Non-catalytic component of the MSL histone acetyltransferase complex, a multiprotein complex that mediates the majority of histone H4 acetylation at 'Lys-16' (H4K16ac), an epigenetic mark that prevents chromatin compaction (PubMed:16227571, PubMed:16543150, PubMed:33837287). The MSL complex is required for chromosome stability and genome integrity by maintaining homeostatic levels of H4K16ac (PubMed:33837287). The MSL complex is also involved in gene dosage by promoting up-regulation of genes expressed by the X chromosome (By similarity). X up-regulation is required to compensate for autosomal biallelic expression (By similarity). The MSL complex also participates in gene dosage compensation by promoting expression of Tsix non-coding RNA (By similarity). Within the MSL complex, acts as a scaffold to tether MSL3 and KAT8 together for enzymatic activity regulation (PubMed:22547026). Greatly enhances MSL2 E3 ubiquitin ligase activity, promoting monoubiquitination of histone H2B at 'Lys-34' (H2BK34Ub) (PubMed:21726816, PubMed:30930284). This modification in turn stimulates histone H3 methylation at 'Lys-4' (H3K4me) and 'Lys-79' (H3K79me) and leads to gene activation, including that of HOXA9 and MEIS1 (PubMed:21726816)","subcellular_location":"Nucleus; Nucleus, nucleoplasm; Nucleus speckle","url":"https://www.uniprot.org/uniprotkb/Q68DK7/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/MSL1","classification":"Not Classified","n_dependent_lines":384,"n_total_lines":1208,"dependency_fraction":0.31788079470198677},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"H2AFZ","stoichiometry":0.2},{"gene":"HIST2H2BE","stoichiometry":0.2},{"gene":"HMGA1","stoichiometry":0.2},{"gene":"NUCKS1","stoichiometry":0.2},{"gene":"PARP1","stoichiometry":0.2},{"gene":"PBK","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/MSL1","total_profiled":1310},"omim":[{"mim_id":"618974","title":"LI-GHORBANI-WEISZ-HUBSHMAN SYNDROME; LIGOWS","url":"https://www.omim.org/entry/618974"},{"mim_id":"614812","title":"NUCLEAR PROTEIN, TRANSCRIPTIONAL REGULATOR, 1; NUPR1","url":"https://www.omim.org/entry/614812"},{"mim_id":"614802","title":"MSL COMPLEX SUBUNIT 2; MSL2","url":"https://www.omim.org/entry/614802"},{"mim_id":"614801","title":"MSL COMPLEX SUBUNIT 1; MSL1","url":"https://www.omim.org/entry/614801"},{"mim_id":"613833","title":"KAT8 REGULATORY NSL COMPLEX SUBUNIT 1-LIKE PROTEIN; KANSL1L","url":"https://www.omim.org/entry/613833"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Enhanced","locations":[{"location":"Nucleoplasm","reliability":"Enhanced"},{"location":"Nuclear speckles","reliability":"Additional"},{"location":"Vesicles","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/MSL1"},"hgnc":{"alias_symbol":["hMSL1","MSL-1","DKFZp686P24239"],"prev_symbol":[]},"alphafold":{"accession":"Q68DK7","domains":[],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q68DK7","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q68DK7-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q68DK7-F1-predicted_aligned_error_v6.png","plddt_mean":57.56},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=MSL1","jax_strain_url":"https://www.jax.org/strain/search?query=MSL1"},"sequence":{"accession":"Q68DK7","fasta_url":"https://rest.uniprot.org/uniprotkb/Q68DK7.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q68DK7/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q68DK7"}},"corpus_meta":[{"pmid":"9409833","id":"PMC_9409833","title":"Drosophila male-specific lethal-2 protein: structure/function analysis and dependence on MSL-1 for chromosome association.","date":"1997","source":"Genetics","url":"https://pubmed.ncbi.nlm.nih.gov/9409833","citation_count":127,"is_preprint":false},{"pmid":"8325488","id":"PMC_8325488","title":"The male-specific lethal-one (msl-1) gene of Drosophila melanogaster encodes a novel protein that associates with the X chromosome in males.","date":"1993","source":"Genetics","url":"https://pubmed.ncbi.nlm.nih.gov/8325488","citation_count":100,"is_preprint":false},{"pmid":"21217699","id":"PMC_21217699","title":"Structural basis for MOF and MSL3 recruitment into the dosage compensation complex by MSL1.","date":"2011","source":"Nature structural & molecular biology","url":"https://pubmed.ncbi.nlm.nih.gov/21217699","citation_count":95,"is_preprint":false},{"pmid":"16547175","id":"PMC_16547175","title":"X-chromosome-wide profiling of MSL-1 distribution and dosage compensation in Drosophila.","date":"2006","source":"Genes & development","url":"https://pubmed.ncbi.nlm.nih.gov/16547175","citation_count":75,"is_preprint":false},{"pmid":"10619853","id":"PMC_10619853","title":"MSL1 plays a central role in assembly of the MSL complex, essential for dosage compensation in Drosophila.","date":"2000","source":"The EMBO journal","url":"https://pubmed.ncbi.nlm.nih.gov/10619853","citation_count":73,"is_preprint":false},{"pmid":"8562424","id":"PMC_8562424","title":"The dosage compensation regulators MLE, MSL-1 and MSL-2 are interdependent since early embryogenesis in Drosophila.","date":"1995","source":"Mechanisms of development","url":"https://pubmed.ncbi.nlm.nih.gov/8562424","citation_count":64,"is_preprint":false},{"pmid":"18086881","id":"PMC_18086881","title":"Incorporation of the noncoding roX RNAs alters the chromatin-binding specificity of the Drosophila MSL1/MSL2 complex.","date":"2007","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/18086881","citation_count":48,"is_preprint":false},{"pmid":"16199870","id":"PMC_16199870","title":"The amino-terminal region of Drosophila MSL1 contains basic, glycine-rich, and leucine zipper-like motifs that promote X chromosome binding, self-association, and MSL2 binding, respectively.","date":"2005","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/16199870","citation_count":47,"is_preprint":false},{"pmid":"24205110","id":"PMC_24205110","title":"Deciphering the binding between Nupr1 and MSL1 and their DNA-repairing activity.","date":"2013","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/24205110","citation_count":39,"is_preprint":false},{"pmid":"23084835","id":"PMC_23084835","title":"Msl1-mediated dimerization of the dosage compensation complex is essential for male X-chromosome regulation in Drosophila.","date":"2012","source":"Molecular cell","url":"https://pubmed.ncbi.nlm.nih.gov/23084835","citation_count":38,"is_preprint":false},{"pmid":"9755201","id":"PMC_9755201","title":"Modulation of MSL1 abundance in female Drosophila contributes to the sex specificity of dosage compensation.","date":"1998","source":"Genetics","url":"https://pubmed.ncbi.nlm.nih.gov/9755201","citation_count":38,"is_preprint":false},{"pmid":"8062831","id":"PMC_8062831","title":"Dosage compensation in Drosophila: the X-chromosomal binding of MSL-1 and MLE is dependent on Sxl activity.","date":"1994","source":"The EMBO journal","url":"https://pubmed.ncbi.nlm.nih.gov/8062831","citation_count":36,"is_preprint":false},{"pmid":"33431797","id":"PMC_33431797","title":"PBK phosphorylates MSL1 to elicit epigenetic modulation of CD276 in nasopharyngeal carcinoma.","date":"2021","source":"Oncogenesis","url":"https://pubmed.ncbi.nlm.nih.gov/33431797","citation_count":27,"is_preprint":false},{"pmid":"34644577","id":"PMC_34644577","title":"Shift in MSL1 alternative polyadenylation in response to DNA damage protects cancer cells from chemotherapeutic agent-induced apoptosis.","date":"2021","source":"Cell reports","url":"https://pubmed.ncbi.nlm.nih.gov/34644577","citation_count":19,"is_preprint":false},{"pmid":"31245767","id":"PMC_31245767","title":"Genetic and physical interactions between the organellar mechanosensitive ion channel homologs MSL1, MSL2, and MSL3 reveal a role for inter-organellar communication in plant development.","date":"2019","source":"Plant direct","url":"https://pubmed.ncbi.nlm.nih.gov/31245767","citation_count":19,"is_preprint":false},{"pmid":"27183194","id":"PMC_27183194","title":"Functional interplay between MSL1 and CDK7 controls RNA polymerase II Ser5 phosphorylation.","date":"2016","source":"Nature structural & molecular biology","url":"https://pubmed.ncbi.nlm.nih.gov/27183194","citation_count":18,"is_preprint":false},{"pmid":"8817458","id":"PMC_8817458","title":"Dosage compensation in Drosophila: the X chromosome binding of MSL-1 and MSL-2 in female embryos is prevented by the early expression of the Sxl gene.","date":"1996","source":"Mechanisms of development","url":"https://pubmed.ncbi.nlm.nih.gov/8817458","citation_count":17,"is_preprint":false},{"pmid":"17335777","id":"PMC_17335777","title":"Characterization of hampin/MSL1 as a node in the nuclear interactome.","date":"2007","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/17335777","citation_count":15,"is_preprint":false},{"pmid":"37279389","id":"PMC_37279389","title":"MSL1 Promotes Liver Regeneration by Driving Phase Separation of STAT3 and Histone H4 and Enhancing Their Acetylation.","date":"2023","source":"Advanced science (Weinheim, Baden-Wurttemberg, Germany)","url":"https://pubmed.ncbi.nlm.nih.gov/37279389","citation_count":14,"is_preprint":false},{"pmid":"23042129","id":"PMC_23042129","title":"Pleiotropic roles of the Msi1-like protein Msl1 in Cryptococcus neoformans.","date":"2012","source":"Eukaryotic cell","url":"https://pubmed.ncbi.nlm.nih.gov/23042129","citation_count":9,"is_preprint":false},{"pmid":"16119455","id":"PMC_16119455","title":"[Tissue specificity of alternative splicing products of mouse mRNA encoding new protein hampin homologous to the Drosophila MSL-1 protein].","date":"2005","source":"Bioorganicheskaia khimiia","url":"https://pubmed.ncbi.nlm.nih.gov/16119455","citation_count":9,"is_preprint":false},{"pmid":"40221412","id":"PMC_40221412","title":"Male-specific lethal 1 (MSL1) promotes Erastin-induced ferroptosis in colon cancer cells by regulating the KCTD12-SLC7A11 axis.","date":"2025","source":"Cell death & disease","url":"https://pubmed.ncbi.nlm.nih.gov/40221412","citation_count":5,"is_preprint":false},{"pmid":"39699942","id":"PMC_39699942","title":"N-terminus of Drosophila melanogaster MSL1 is critical for dosage compensation.","date":"2024","source":"eLife","url":"https://pubmed.ncbi.nlm.nih.gov/39699942","citation_count":4,"is_preprint":false},{"pmid":"24913909","id":"PMC_24913909","title":"Two distinct nuclear localization signals in mammalian MSL1 regulate its function.","date":"2014","source":"Journal of cellular biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/24913909","citation_count":4,"is_preprint":false},{"pmid":"30930284","id":"PMC_30930284","title":"Analysis of histone ubiquitylation by MSL1/MSL2 proteins in vitro.","date":"2019","source":"Archives of biochemistry and biophysics","url":"https://pubmed.ncbi.nlm.nih.gov/30930284","citation_count":4,"is_preprint":false},{"pmid":"34426916","id":"PMC_34426916","title":"Mutations of Phosphorylation Sites in MSL1 Protein Do Not Affect Dosage Compensation in Drosophila melanogaster.","date":"2021","source":"Doklady. Biochemistry and biophysics","url":"https://pubmed.ncbi.nlm.nih.gov/34426916","citation_count":1,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":11991,"output_tokens":4881,"usd":0.054594,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":13079,"output_tokens":4355,"usd":0.087135,"stage2_stop_reason":"end_turn"},"total_usd":0.141729,"stage1_batch_id":"msgbatch_01BbTCMyrRPyhtEq6b1MdwCN","stage2_batch_id":"msgbatch_011dEed5bbxYvTAaQWKJevxu","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1993,\n      \"finding\": \"MSL1 protein associates with hundreds of sites along the length of the X chromosome in male (but not female) nuclei, consistent with a direct role in increasing X-linked gene transcription in males.\",\n      \"method\": \"Immunostaining/chromosome localization assay\",\n      \"journal\": \"Genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct localization experiment with sex-specific functional context, single lab\",\n      \"pmids\": [\"8325488\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"X-chromosomal association of MSL-1 depends on wild-type function of the other MSL proteins (MLE, MSL-2, MSL-3), indicating MSL-1 participates in a multi-subunit complex; binding is negatively regulated by the master sex-determination gene Sxl.\",\n      \"method\": \"Genetic analysis; immunostaining in mutant backgrounds\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis with direct localization readout, single lab\",\n      \"pmids\": [\"8062831\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"MSL-1, MSL-2, MLE, and histone H4Ac16 are mutually interdependent for sub-nuclear (X chromosome) localization from early embryogenesis; loss of any one MSL protein abolishes co-localization of the others.\",\n      \"method\": \"Immunostaining of embryos in msl mutant backgrounds\",\n      \"journal\": \"Mechanisms of development\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis with direct localization readout, single lab\",\n      \"pmids\": [\"8562424\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"MSL-2 binding to the X chromosome depends on MSL-1; the two proteins co-localize precisely, suggesting they function together to associate with the X. The MSL-2 RING finger domain is essential for MSL-2 function in this complex.\",\n      \"method\": \"Immunostaining in msl mutant backgrounds; EMS suppressor screen; site-directed mutagenesis of MSL-2\",\n      \"journal\": \"Genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis plus direct localization, single lab\",\n      \"pmids\": [\"9409833\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"MSL1 protein abundance in females is reduced compared to males through two mechanisms: predominantly post-translational protein instability and secondarily reduced protein synthesis. Overcoming both controls by co-overexpressing MSL1 and MSL2 in females causes 100% female-specific lethality.\",\n      \"method\": \"Western blot quantification; overexpression genetics in Drosophila\",\n      \"journal\": \"Genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — biochemical quantification plus genetic functional readout, single lab\",\n      \"pmids\": [\"9755201\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"MSL1 serves as a scaffold for MSL complex assembly: its N-terminal domain interacts with MSL2, and its C-terminal domain co-purifies with both MSL3 and MOF (histone acetyltransferase). Dominant-negative overexpression of either domain causes male-specific lethality, and the C-terminal domain shows similarity to the transcription co-activator CBP.\",\n      \"method\": \"FLAG affinity purification; GST pulldown; co-immunoprecipitation with HA-tagged MSL3; dominant-negative overexpression genetics\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal binding assays (FLAG pulldown, GST pulldown, co-IP) plus genetic dominant-negative phenotype, independently consistent with structural data\",\n      \"pmids\": [\"10619853\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"The N-terminal region of Drosophila MSL1 contains three functionally distinct motifs: (1) a basic motif required for binding to ~30 high-affinity X-chromosomal sites; (2) a glycine-rich motif mediating MSL1 self-association in vitro and binding to the assembled MSL complex; (3) a leucine zipper-like motif that binds MSL2 and is required for X chromosome association.\",\n      \"method\": \"In vitro self-association assay; co-immunoprecipitation; immunostaining of transgenic flies expressing N-terminal domain fragments; site-directed mutagenesis\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — in vitro binding assays plus mutagenesis plus in vivo localization, multiple orthogonal methods, single lab\",\n      \"pmids\": [\"16199870\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"ChIP-chip analysis reveals MSL-1 binding profile across the male X chromosome; MSL-1 binding does not strictly correlate with transcriptional output of target genes, suggesting additional factors determine dosage-compensated status beyond direct MSL-1 binding.\",\n      \"method\": \"Chromatin immunoprecipitation coupled with DNA microarray (ChIP-chip)\",\n      \"journal\": \"Genes & development\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genome-wide ChIP-chip with functional interpretation, single lab\",\n      \"pmids\": [\"16547175\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Incorporation of roX noncoding RNAs into the MSL complex alters its chromatin-binding specificity. The amino-terminal RING finger domain of MSL2, acting as a complex with MSL1, mediates binding to the heterochromatic chromocenter and a few chromosomal arm sites; this requires the same basic motif of MSL1 needed for high-affinity X-chromosomal binding.\",\n      \"method\": \"Transgenic expression of MSL2 domain fragments; immunostaining; co-immunoprecipitation\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — domain dissection with localization and binding assays, single lab\",\n      \"pmids\": [\"18086881\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Mammalian MSL1 (hampin) interacts with MYST1/MOF, TTC4, KIAA0103, NOP17, and transcription factor GCBP as identified by yeast two-hybrid; the majority of interactions were confirmed by in vitro pulldown of bacterially expressed proteins.\",\n      \"method\": \"Yeast two-hybrid screen; in vitro pulldown assay\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — yeast two-hybrid confirmed by pulldown, multiple interactors, single lab\",\n      \"pmids\": [\"17335777\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Crystal structures of mammalian MSL1 binary complexes with MSL3 and MOF reveal: MSL1 interacts with MSL3 as an extended chain forming an extensive hydrophobic interface; the MSL1-MOF interface involves electrostatic interactions between the MOF HAT domain and a long helix of MSL1. Selective disruption of Msl1-Msl3 or Msl1-Mof interactions in Drosophila severely impairs MSL complex targeting to gene bodies and high-affinity sites without affecting promoter binding.\",\n      \"method\": \"X-ray crystallography; structure-based mutagenesis; ChIP in Drosophila\",\n      \"journal\": \"Nature structural & molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structures with functional validation by mutagenesis and ChIP, multiple orthogonal methods\",\n      \"pmids\": [\"21217699\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Crystal structure of the MSL1/MSL2 core shows two MSL2 subunits binding to an MSL1 dimer; MSL1 dimerization is MSL2-independent, but MSL2 can only interact with the MSL1 dimer. Structure-based mutants show Msl1 dimerization is essential for MSL complex targeting to and spreading along X-linked gene bodies. Additionally, MSL1 is a substrate for MSL2 E3 ubiquitin ligase activity. MSL1 binding to promoters is independent of its dimerization status and other MSL proteins.\",\n      \"method\": \"X-ray crystallography; structure-based mutagenesis; ChIP; in vitro ubiquitylation assay\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure with mutagenesis, in vitro enzymatic assay, and ChIP validation, multiple orthogonal methods\",\n      \"pmids\": [\"23084835\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Human MSL1 and Nupr1 are recruited to the nucleus in response to DNA damage and form a complex essential for cell survival under cisplatin treatment. MSL1 binds Nupr1 with moderate affinity (Kd ~2.8 µM) in an entropically driven process. MSL1 does not bind undamaged DNA but binds chemically damaged DNA with moderate affinity (~1.2 µM).\",\n      \"method\": \"Biophysical binding assays (ITC, fluorescence); NMR; cell viability assays; nuclear co-localization\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple biophysical methods (ITC, NMR, fluorescence) establishing binding affinities, single lab\",\n      \"pmids\": [\"24205110\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Mammalian MSL1 contains two distinct nuclear localization signals (NLS): a novel NLS common to all isoforms, and a previously known bipartite NLS in the PEHE domain. Isoforms possessing both NLS localize to sub-nuclear foci and can direct co-chaperone TTC4 there; all isoforms retain the ability to affect H4K16 acetylation.\",\n      \"method\": \"Subcellular localization of MSL1 isoforms; NLS deletion constructs; co-localization with TTC4; H4K16 acetylation assay\",\n      \"journal\": \"Journal of cellular biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct localization experiments with functional consequence (H4K16ac), single lab\",\n      \"pmids\": [\"24913909\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"MSL1 interacts functionally with CDK7 (a subunit of the CAK complex of TFIIH); MSL1 depletion leads to decreased Ser5 phosphorylation of RNA polymerase II. MSL1 is itself a phosphoprotein, and transgenic flies expressing MSL1 phosphomutants show mislocalization of MOF and reduced H4K16 acetylation, causing male lethality.\",\n      \"method\": \"Genetic interaction; biochemical interaction assays; phospho-Pol II ChIP; transgenic phosphomutant Drosophila\",\n      \"journal\": \"Nature structural & molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic and biochemical epistasis with multiple functional readouts (Pol II Ser5 phosphorylation, MOF localization, H4K16ac, male lethality), replicated across two Drosophila species\",\n      \"pmids\": [\"27183194\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Purified MSL1/MSL2 complex ubiquitylates histone H2B (at K34) in vitro in a substrate-configuration-dependent manner; MSL1/2 efficiently ubiquitylates free histone substrates but very poorly modifies intact nucleosomes, implying a requirement for nucleosome structural alteration for efficient H2BK34 ubiquitylation.\",\n      \"method\": \"In vitro ubiquitylation assay with purified proteins; nucleosome gel-mobility shift assay\",\n      \"journal\": \"Archives of biochemistry and biophysics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — in vitro reconstituted enzymatic assay, single lab, single study\",\n      \"pmids\": [\"30930284\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"PBK kinase phosphorylates MSL1 and enhances MSL1 interaction with MSL2, MSL3, and KAT8 (components of the MSL complex). This promotes MSL complex enrichment on the CD276 promoter, leading to increased H4K16 acetylation and CD276 transcriptional activation in nasopharyngeal carcinoma cells.\",\n      \"method\": \"Co-immunoprecipitation; ChIP; phosphorylation assay; knockdown/overexpression in cancer cells; H4K16ac western blot\",\n      \"journal\": \"Oncogenesis\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP and ChIP with functional readout, single lab, multiple methods\",\n      \"pmids\": [\"33431797\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Phosphorylation-site mutations in Drosophila MSL1 (replacing phosphorylatable residues) do not affect specific binding of the dosage compensation complex to the male X chromosome or its functional activity, indicating these particular phosphorylation sites are dispensable for dosage compensation.\",\n      \"method\": \"Transgenic Drosophila expressing MSL1 phosphomutants; immunostaining\",\n      \"journal\": \"Doklady. Biochemistry and biophysics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — direct in vivo negative result with transgenic mutants, single lab\",\n      \"pmids\": [\"34426916\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"MSL1 forms liquid-liquid phase separation condensates with STAT3 or histone H4 in hepatocytes, enriching acetyl-CoA (Ac-CoA) in these condensates. Ac-CoA in turn enhances MSL1 condensate formation, synergistically promoting acetylation of STAT3 K685 and H4K16, thereby stimulating liver regeneration after partial hepatectomy.\",\n      \"method\": \"Phase separation assays; co-immunoprecipitation; acetylation assays; partial hepatectomy mouse model; MSL1 knockdown/overexpression\",\n      \"journal\": \"Advanced science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — phase separation assays with functional in vivo readout, single lab\",\n      \"pmids\": [\"37279389\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"The N-terminal region of Drosophila MSL1 (amino acids 3–7) is critical for interaction with roX2 RNA and for MSL complex binding to high-affinity sites (HAS) on the X chromosome. MSL1GS (N-terminal substitution mutant) binds promoters like wild-type MSL1 but fails to co-bind MSL2 and MSL3 at HAS; overexpression of MSL2 partially restores dosage compensation, indicating roX RNA interaction with MSL1 N-terminus is essential for efficient MSL complex assembly at HAS.\",\n      \"method\": \"Transgenic Drosophila expressing MSL1 deletion/substitution mutants; ChIP; immunostaining; RNA immunoprecipitation\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — structure-function dissection with multiple orthogonal methods (ChIP, immunostaining, RIP, genetics), rigorous in vivo validation\",\n      \"pmids\": [\"39699942\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"MSL1 negatively regulates KCTD12 expression in colon cancer cells; Erastin-induced ferroptosis suppresses MSL1 expression leading to KCTD12 upregulation, which in turn reduces SLC7A11 levels, promoting ferroptosis through altered ROS, GSH, and MDA levels.\",\n      \"method\": \"Knockdown/overexpression studies; biochemical assays for ROS, GSH, MDA; ferroptosis cell death assay\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, knockdown/overexpression without direct molecular mechanism between MSL1 and KCTD12\",\n      \"pmids\": [\"40221412\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"MSL1 functions as the central scaffold protein of the MSL histone acetyltransferase complex: its N-terminal basic motif mediates DNA/roX RNA binding and X-chromosome high-affinity site recognition, a glycine-rich motif mediates MSL1 self-dimerization (essential for complex spreading along the X), and leucine zipper-like and C-terminal (PEHE) domains recruit MSL2, MSL3, and the acetyltransferase KAT8/MOF respectively, as established by crystal structures and mutagenesis; MSL1 dimerization is required for MSL2 engagement and X-chromosomal spreading; MSL1 also interacts with CDK7/TFIIH to promote RNA Pol II Ser5 phosphorylation and is itself regulated by phosphorylation (by PBK) and ubiquitylation (by MSL2 E3 ligase), while in mammals it additionally forms phase-separation condensates to facilitate H4K16 and STAT3 acetylation.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"MSL1 is the central scaffold of the MSL histone acetyltransferase complex that drives X-chromosome dosage compensation in male Drosophila, decorating hundreds of X-linked sites in a sex-specific manner and acting interdependently with MSL2, MSL3, MLE and H4K16 acetylation [#0, #2, #5]. As a scaffold, MSL1 uses spatially distinct regions: an N-terminal basic motif that recognizes ~30 high-affinity X-chromosomal sites and engages roX noncoding RNA, a glycine-rich motif that mediates MSL1 self-association, and a leucine-zipper-like motif that binds MSL2, while its C-terminal region co-purifies with MSL3 and the acetyltransferase MOF/KAT8 [#5, #6, #19]. Crystal structures define these interfaces and show that MSL2 binds only an MSL1 dimer, with MSL1 dimerization being essential for complex targeting to and spreading along X-linked gene bodies, whereas promoter binding is dimerization- and partner-independent [#10, #11]. The MSL1/MSL2 module also carries MSL2-dependent enzymatic outputs: MSL1 is a substrate for MSL2 E3 ubiquitin ligase activity, and the purified MSL1/MSL2 complex ubiquitylates histone H2B at K34 on free histone substrates [#11, #15]. MSL1 couples chromatin modification to transcription by interacting with CDK7/TFIIH to promote RNA Pol II Ser5 phosphorylation, and its own phosphorylation state controls MOF localization and H4K16 acetylation [#14]. In mammals MSL1 retains MOF binding and H4K16-acetylation activity, localizes to sub-nuclear foci via two NLS, and forms liquid-liquid phase-separation condensates with STAT3 or histone H4 that concentrate acetyl-CoA to promote STAT3 K685 and H4K16 acetylation during liver regeneration [#9, #13, #18]. MSL1 is additionally recruited to the nucleus upon DNA damage where it binds damaged DNA and Nupr1 to support cell survival [#12].\",\n  \"teleology\": [\n    {\n      \"year\": 1993,\n      \"claim\": \"Established that MSL1 is a chromatin-associated factor acting specifically in males, linking it to X-linked transcriptional upregulation.\",\n      \"evidence\": \"Sex-specific immunostaining of MSL1 along the X chromosome in Drosophila nuclei\",\n      \"pmids\": [\"8325488\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Did not define molecular partners or mechanism of X recognition\", \"No biochemical demonstration of a complex\"]\n    },\n    {\n      \"year\": 1995,\n      \"claim\": \"Showed MSL1 functions within a mutually dependent multi-subunit assembly, not as an isolated factor, by demonstrating reciprocal localization requirements with MSL2, MSL3, MLE and H4K16ac.\",\n      \"evidence\": \"Immunostaining in msl mutant backgrounds across embryogenesis\",\n      \"pmids\": [\"8062831\", \"8562424\", \"9409833\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Interdependence was genetic/localization-based, not direct biochemical contact mapping\", \"Order of assembly unresolved\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Defined how MSL1 dosage is restricted to males, identifying post-translational instability and reduced synthesis as the controls preventing female complex assembly.\",\n      \"evidence\": \"Western quantification and co-overexpression genetics in Drosophila\",\n      \"pmids\": [\"9755201\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular machinery of female-specific instability not identified\", \"Did not link to ubiquitylation directly\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Established MSL1 as the scaffold by mapping an N-terminal MSL2-binding region and a C-terminal region that co-purifies with MSL3 and MOF, giving the complex a modular architecture.\",\n      \"evidence\": \"FLAG/GST pulldowns, co-IP, and dominant-negative domain overexpression in Drosophila\",\n      \"pmids\": [\"10619853\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Domain boundaries were coarse without structural detail\", \"Stoichiometry not defined\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Resolved the N-terminus into three functional motifs, separating high-affinity-site DNA binding, self-association, and MSL2 binding.\",\n      \"evidence\": \"In vitro self-association, co-IP, and transgenic localization of N-terminal fragments with mutagenesis\",\n      \"pmids\": [\"16199870\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not establish how self-association couples to spreading at atomic resolution\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Defined the chromatin-binding behavior and partner repertoire, showing MSL-1 binding does not strictly predict transcriptional output and identifying mammalian MSL1 interactors including MOF and TTC4.\",\n      \"evidence\": \"ChIP-chip on the male X; yeast two-hybrid with in vitro pulldown confirmation\",\n      \"pmids\": [\"16547175\", \"17335777\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Additional determinants of dosage-compensated status not identified\", \"Functional relevance of several Y2H interactors untested\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Provided structural mechanism: MSL1 dimerizes independently of MSL2, MSL2 binds only the dimer, and dimerization is required for targeting and spreading along gene bodies but not promoter binding; also identified MSL1 as an MSL2 ubiquitylation substrate.\",\n      \"evidence\": \"X-ray crystallography of MSL1/MSL2 and MSL1/MSL3 and MSL1/MOF interfaces, structure-based mutagenesis, ChIP, in vitro ubiquitylation\",\n      \"pmids\": [\"21217699\", \"23084835\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional consequence of MSL1 ubiquitylation in vivo unresolved\", \"How dimerization drives spreading mechanistically not fully defined\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Extended MSL1 function into the DNA-damage response, showing it binds damaged DNA and Nupr1 to support survival under genotoxic stress.\",\n      \"evidence\": \"ITC, NMR, fluorescence binding, nuclear co-localization and cell viability under cisplatin\",\n      \"pmids\": [\"24205110\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Link to the canonical MSL acetyltransferase function unclear\", \"Downstream repair pathway not defined\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Connected MSL1 to transcriptional machinery and its own regulation, showing it engages CDK7/TFIIH to promote Pol II Ser5 phosphorylation and that MSL1 phosphorylation controls MOF localization and H4K16ac.\",\n      \"evidence\": \"Genetic/biochemical interaction, phospho-Pol II ChIP, transgenic phosphomutant Drosophila across two species\",\n      \"pmids\": [\"27183194\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Kinase responsible in vivo not pinned down in this study\", \"Direct CDK7 contact interface unmapped\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Demonstrated an intrinsic enzymatic output of the MSL1/MSL2 module, ubiquitylating H2BK34 with strong dependence on substrate configuration.\",\n      \"evidence\": \"In vitro ubiquitylation with purified proteins and nucleosome gel-shift\",\n      \"pmids\": [\"30930284\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Poor activity on intact nucleosomes leaves physiological substrate unclear\", \"Single in vitro study\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Identified PBK as a kinase that phosphorylates MSL1 to enhance complex assembly and target-gene activation, while a separate Drosophila study showed certain phosphosites are dispensable for dosage compensation.\",\n      \"evidence\": \"Co-IP/ChIP/phosphorylation assays in carcinoma cells; transgenic phosphomutant immunostaining in Drosophila\",\n      \"pmids\": [\"33431797\", \"34426916\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Which specific MSL1 residues mediate context-dependent effects not reconciled across systems\", \"Generality of PBK regulation beyond cancer cells untested\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Revealed a phase-separation mechanism in mammals, with MSL1 condensates concentrating acetyl-CoA to promote STAT3 and H4K16 acetylation during liver regeneration.\",\n      \"evidence\": \"Phase separation and acetylation assays, co-IP, partial hepatectomy mouse model\",\n      \"pmids\": [\"37279389\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Condensate composition relative to canonical MSL complex undefined\", \"Sequence determinants of MSL1 phase separation unmapped\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Established that the extreme MSL1 N-terminus mediates roX2 RNA binding required for complex co-binding at high-affinity sites, distinguishing RNA-dependent HAS recruitment from RNA-independent promoter binding.\",\n      \"evidence\": \"Transgenic MSL1 substitution mutants with ChIP, immunostaining, and RNA immunoprecipitation\",\n      \"pmids\": [\"39699942\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of MSL1 N-terminus/roX2 contact not determined\", \"How RNA binding integrates with dimerization-driven spreading unresolved\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Proposed an MSL1 role in ferroptosis via negative regulation of KCTD12 and the SLC7A11 axis in colon cancer.\",\n      \"evidence\": \"Knockdown/overexpression with ROS, GSH, MDA and ferroptosis assays\",\n      \"pmids\": [\"40221412\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No direct molecular mechanism linking MSL1 to KCTD12 established\", \"Single lab, indirect readouts only\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How the canonical MSL acetyltransferase scaffold function integrates with the mammalian-specific activities (DNA-damage response, phase separation, ferroptosis regulation) into a unified model remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No structural model of the full mammalian complex with RNA\", \"Physiological H2BK34 ubiquitylation context undefined\", \"Mechanistic link between condensate formation and chromatin targeting unknown\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [5, 6, 10, 11]},\n      {\"term_id\": \"GO:0003723\", \"supporting_discovery_ids\": [8, 19]},\n      {\"term_id\": \"GO:0003677\", \"supporting_discovery_ids\": [6, 12]},\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [11, 15]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0000228\", \"supporting_discovery_ids\": [0, 2, 7]},\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [12, 13]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-4839726\", \"supporting_discovery_ids\": [5, 10, 14]},\n      {\"term_id\": \"R-HSA-74160\", \"supporting_discovery_ids\": [0, 14, 16]}\n    ],\n    \"complexes\": [\"MSL complex\"],\n    \"partners\": [\"MSL2\", \"MSL3\", \"KAT8/MOF\", \"MLE\", \"CDK7\", \"STAT3\", \"Nupr1\", \"PBK\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":7,"faith_pct":100.0}}