{"gene":"MSL3","run_date":"2026-06-10T02:59:51","timeline":{"discoveries":[{"year":2011,"finding":"MSL1 acts as a scaffold for MSL complex assembly: it recruits MSL3 via an extended hydrophobic chain interface and MOF (HAT domain) via electrostatic interactions with a long MSL1 helix. Disruption of these interactions severely impairs MSL1 targeting to the body of dosage-compensated genes and several high-affinity sites, without affecting promoter binding.","method":"X-ray crystallography of binary MSL1-MSL3 and MSL1-MOF complexes, combined with selective point mutagenesis and ChIP analysis in Drosophila","journal":"Nature structural & molecular biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structures with mutagenesis validated by in vivo ChIP; multiple orthogonal methods in a single rigorous study","pmids":["21217699"],"is_preprint":false},{"year":2010,"finding":"The MSL3 chromodomain co-recognizes DNA and the H4K20 monomethyl mark: the DNA minor groove accommodates the histone H4 tail, and monomethyllysine inserts into a four-residue aromatic cage in MSL3. H4K16 acetylation antagonizes this MSL3 binding, suggesting MSL spreading is regulated by a combination of post-translational modifications.","method":"X-ray crystal structure of a ternary MSL3 chromodomain–DNA–H4K20me1 peptide complex; in vitro binding assays","journal":"Nature structural & molecular biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — atomic-resolution ternary crystal structure with biochemical binding validation in a single rigorous study","pmids":["20657587"],"is_preprint":false},{"year":2008,"finding":"The MSL3 chromodomain is required for the second targeting step of dosage compensation (spreading from chromatin entry sites to active gene bodies marked by H3K36me3): chromodomain mutants retain binding to entry sites but lose spreading, and show reduced preferential affinity for H3K36me3-containing nucleosomes in vitro.","method":"ChIP-chip analysis of MSL3 chromodomain mutants in Drosophila; in vitro nucleosome-binding assays with H3K36me3 nucleosomes","journal":"Nature structural & molecular biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal in vivo (ChIP-chip) and in vitro (nucleosome binding) evidence; multiple orthogonal methods","pmids":["19029895"],"is_preprint":false},{"year":2010,"finding":"The human MSL3 chromo-barrel domain binds preferentially to H4K20me1 and H4K20me2 peptides via an aromatic cage (Tyr-31, Phe-56, Trp-59, Trp-63). Mutation of Tyr-31 weakens H4K20me1 binding in vitro and compromises male survival in Drosophila, linking the methyllysine-binding cage to MSL complex chromatin targeting.","method":"X-ray crystallography of human MSL3 chromo-barrel domain (2.5 Å); in vitro peptide-binding assays; Drosophila male viability rescue assays with point mutants","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure combined with mutagenesis and in vitro binding, validated in vivo in Drosophila","pmids":["20943666"],"is_preprint":false},{"year":2003,"finding":"MOF acetylates MSL-3 at a single lysine residue adjacent to its chromodomain; this acetylation regulates MSL-3's interaction with roX2 RNA and its localization to the X chromosome. RPD3 deacetylase complex interacts with MSL-3 and can reverse this acetylation, suggesting a regulated acetylation–deacetylation cycle controls DCC spreading.","method":"RNAi knockdown of individual DCC components; mass spectrometry identification of acetylation site; co-immunoprecipitation of RPD3 with MSL-3; RNA-binding and localization assays","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — MS-identified modification site, Co-IP of writer (MOF) and eraser (RPD3), functional RNA-binding and localization readouts; multiple orthogonal methods","pmids":["12769850"],"is_preprint":false},{"year":2005,"finding":"The C-terminal MRG domain of MSL3 forms an integrated domain required for interaction with MSL1, and this interaction mediates activation of MOF's nucleosomal histone acetyltransferase activity in vitro and targeting of MSL3 to the X-chromosomal territory in vivo. Nucleic acid binding determinants reside separately in the N-terminus and are dispensable for DCC assembly.","method":"Domain deletion analysis; in vitro HAT activity assays; immunofluorescence localization in Drosophila cells","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — domain mutagenesis combined with in vitro enzymatic assay and in vivo localization; multiple orthogonal methods, replicated MSL1 interaction theme","pmids":["15988010"],"is_preprint":false},{"year":2006,"finding":"MSL-3 targeting to the X chromosome (mediated by the MRG domain) and transcriptional upregulation of X-linked genes (requiring the chromo-barrel domain and polar region) are two functionally separable activities of MSL-3.","method":"Domain truncation/deletion mutants assayed by immunofluorescence for X-chromosome localization and quantitative RT-PCR for X-linked gene expression; viability assays in Drosophila","journal":"EMBO reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — clean domain-separation experiment in vivo, single lab, two readouts (localization + transcription)","pmids":["16547465"],"is_preprint":false},{"year":2018,"finding":"Pathogenic MSL3 variants in humans disrupt MSL complex assembly and activity, causing a pronounced loss of bulk H4K16ac in vivo and global transcriptome alterations. HDAC inhibitor treatment can partially rebalance acetylation and alleviate molecular/cellular phenotypes in patient-derived cells.","method":"Patient-derived cell lines; western blot for H4K16ac; MSL complex co-immunoprecipitation; RNA-seq; HDAC inhibitor rescue experiments","journal":"Nature genetics","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (Co-IP, chromatin mark quantification, transcriptomics, pharmacological rescue) in patient cells; published in high-tier journal","pmids":["30224647"],"is_preprint":false},{"year":2022,"finding":"In Drosophila female germline, Msl3 acts independently of the rest of the MSL complex to read H3K36me3 (deposited by Set2) and, together with the ATAC histone acetyltransferase complex, promotes transcription of genes including RpS19b; RpS19b upregulation is required for translation of Rbfox1, a meiotic cell cycle entry factor, thereby regulating germline stem cell differentiation.","method":"Genetic epistasis (msl3, set2, ATAC mutants); RNA-seq; ribosome profiling/translation assays; immunofluorescence in Drosophila ovaries","journal":"Development (Cambridge, England)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis with defined molecular pathway, single lab, multiple readouts (transcription + translation)","pmids":["34878097"],"is_preprint":false},{"year":1999,"finding":"A human gene (MSL3L1, now MSL3) was identified encoding a protein with homology to Drosophila MSL-3 in three regions including two putative chromo domains, mapping to Xp22.3.","method":"Database homology search; genomic mapping; sequence analysis","journal":"Genomics","confidence":"Low","confidence_rationale":"Tier 4 / Weak — computational/sequence-based identification only; no functional experiments performed on the human protein","pmids":["10395802"],"is_preprint":false},{"year":2023,"finding":"Conditional loss of Msl3 (chromodomain-disrupting allele) in mouse spermatogonia does NOT cause spermatogenesis defects or changes in expression of meiosis-related genes, indicating that MSL3 chromodomain function is dispensable for meiotic entry in rodents.","method":"Stra8-iCre conditional knockout mouse; histology; single-cell RNA-seq analysis","journal":"Developmental dynamics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — clean conditional KO with defined cellular readout; negative result robustly established in vivo","pmids":["37847071"],"is_preprint":false}],"current_model":"MSL3 is a chromatin-associated subunit of the MSL dosage compensation complex whose chromo-barrel domain binds H4K20me1/me2 and H3K36me3 on active chromatin to direct spreading of the complex along the X chromosome, while its C-terminal MRG domain docks onto MSL1 (the complex scaffold) to activate MOF's nucleosomal H4K16 acetyltransferase activity; MOF in turn acetylates MSL3 itself at a single lysine adjacent to its chromodomain—an acetylation reversed by RPD3—to regulate roX RNA binding and X-chromosomal localization, and pathogenic human MSL3 variants that disrupt complex assembly reduce bulk H4K16ac and cause the Basilicata-Akhtar neurodevelopmental syndrome."},"narrative":{"mechanistic_narrative":"MSL3 is a chromatin-reader subunit of the MSL dosage compensation complex that couples recognition of active-chromatin histone marks to spreading of the complex and H4K16 acetylation along the X chromosome [PMID:21217699, PMID:19029895]. Its N-terminal chromo-barrel domain engages methylated histone tails through a four-residue aromatic cage, binding H4K20me1/me2 and co-recognizing DNA, while H4K16 acetylation antagonizes this engagement, providing a modification-sensitive switch for complex spreading [PMID:20657587, PMID:20943666]; the same domain confers preferential affinity for H3K36me3 nucleosomes and is required for the second targeting step that moves the complex from chromatin entry sites into transcribed gene bodies [PMID:19029895]. The C-terminal MRG domain docks onto the MSL1 scaffold, and this contact both targets MSL3 to the X-chromosomal territory and activates MOF's nucleosomal H4K16 acetyltransferase activity, with X-targeting and transcriptional activation being functionally separable activities of the protein [PMID:21217699, PMID:15988010, PMID:16547465]. MSL3 is itself acetylated by MOF at a single lysine adjacent to its chromodomain and deacetylated by the RPD3 complex, an acetylation-deacetylation cycle that tunes roX2 RNA binding and X-chromosomal localization [PMID:12769850]. Beyond canonical dosage compensation, MSL3 reads H3K36me3 independently of the complex to promote ATAC-dependent transcription during Drosophila germline stem cell differentiation [PMID:34878097]. Pathogenic human MSL3 variants disrupt complex assembly, reduce bulk H4K16ac, and cause the Basilicata-Akhtar neurodevelopmental syndrome, with HDAC inhibition partially rebalancing acetylation in patient cells [PMID:30224647].","teleology":[{"year":1999,"claim":"Establishing a human ortholog of Drosophila MSL-3 was the first step toward asking whether dosage-compensation machinery is conserved in humans.","evidence":"database homology search and genomic mapping of MSL3L1 to Xp22.3","pmids":["10395802"],"confidence":"Low","gaps":["computational identification only; no functional experiments on the human protein","chromo-domain binding specificity not tested","complex membership not demonstrated"]},{"year":2003,"claim":"Identifying MSL-3 as an acetylation substrate of MOF revealed that the reader is itself regulated by a writer-eraser cycle controlling its RNA binding and X localization.","evidence":"RNAi of DCC components, MS mapping of the acetylation site, RPD3 co-IP, and roX2 RNA-binding/localization assays in Drosophila","pmids":["12769850"],"confidence":"High","gaps":["structural basis of how acetylation alters roX2 binding not resolved","in vivo kinetics of the acetylation-deacetylation cycle unknown"]},{"year":2005,"claim":"Mapping the MRG domain as the MSL1-binding module showed how MSL3 is physically integrated into the complex and stimulates MOF catalysis, separating assembly from nucleic-acid binding.","evidence":"domain deletion analysis, in vitro nucleosomal HAT assays, and immunofluorescence localization in Drosophila cells","pmids":["15988010"],"confidence":"High","gaps":["atomic detail of the MRG-MSL1 interface not yet defined here","mechanism of MOF activation by the interaction not resolved"]},{"year":2006,"claim":"Demonstrating that X-chromosome targeting (MRG) and transcriptional upregulation (chromo-barrel/polar region) are separable activities clarified that MSL3 contributes two distinct functions to dosage compensation.","evidence":"domain truncation mutants assayed by immunofluorescence, RT-PCR, and viability in Drosophila","pmids":["16547465"],"confidence":"Medium","gaps":["single-lab domain-separation result","molecular basis of the polar region's contribution to activation unknown"]},{"year":2008,"claim":"Assigning the chromodomain to the spreading step distinguished chromatin entry from propagation, showing the reader drives movement into H3K36me3-marked gene bodies.","evidence":"ChIP-chip of chromodomain mutants and in vitro H3K36me3 nucleosome-binding assays in Drosophila","pmids":["19029895"],"confidence":"High","gaps":["relative contribution of H3K36me3 versus H4K20 marks to spreading not disentangled","structural basis of H3K36me3 recognition not solved here"]},{"year":2010,"claim":"Atomic structures of the chromo-barrel domain defined the aromatic cage and showed dual recognition of DNA and methylated H4K20, with H4K16ac acting as an antagonistic switch.","evidence":"ternary MSL3 chromodomain-DNA-H4K20me1 crystal structure, human MSL3 chromo-barrel structure, peptide-binding assays, and Drosophila viability rescue with cage mutants","pmids":["20657587","20943666"],"confidence":"High","gaps":["in vivo hierarchy among H4K20me1/me2 and H3K36me3 as the operative spreading mark unresolved","how H4K16ac antagonism is integrated with productive acetylation during spreading not defined"]},{"year":2011,"claim":"Crystal structures of MSL1 binary complexes established MSL1 as the scaffold that recruits both MSL3 and MOF, defining the assembly architecture required for targeting gene bodies.","evidence":"X-ray structures of MSL1-MSL3 and MSL1-MOF complexes with point mutagenesis and ChIP in Drosophila","pmids":["21217699"],"confidence":"High","gaps":["full quaternary architecture with roX RNA not resolved","how scaffold contacts couple to MOF catalytic activation not fully defined"]},{"year":2018,"claim":"Linking pathogenic human MSL3 variants to disrupted complex assembly, reduced H4K16ac, and a neurodevelopmental syndrome translated the Drosophila mechanism into human disease and a candidate therapeutic axis.","evidence":"patient-derived cells with H4K16ac western blot, MSL complex co-IP, RNA-seq, and HDAC inhibitor rescue","pmids":["30224647"],"confidence":"High","gaps":["tissue- and neuron-specific consequences in patients not defined","long-term efficacy of HDAC inhibition not established"]},{"year":2022,"claim":"Showing a complex-independent role for Msl3 in reading H3K36me3 with ATAC during germline differentiation expanded its function beyond canonical X dosage compensation.","evidence":"genetic epistasis (msl3, set2, ATAC), RNA-seq, ribosome profiling, and immunofluorescence in Drosophila ovaries","pmids":["34878097"],"confidence":"Medium","gaps":["single-lab study in one tissue","direct biochemical demonstration of Msl3-ATAC association not shown"]},{"year":2023,"claim":"A negative result in mouse spermatogonia showed that MSL3 chromodomain function is dispensable for meiotic entry in rodents, indicating the germline role is not conserved as in flies.","evidence":"Stra8-iCre conditional chromodomain-disrupting knockout with histology and single-cell RNA-seq in mouse","pmids":["37847071"],"confidence":"Medium","gaps":["non-chromodomain MSL3 functions in mouse germline not tested","compensatory redundancy not excluded"]},{"year":null,"claim":"How chromatin-mark reading, MSL3 autoacetylation, roX RNA binding, and MOF activation are integrated in real time to direct complex spreading remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["no integrated dynamic model coupling mark recognition to acetylation output","human MSL3 mechanism characterized mainly through disease variants rather than reconstitution","structural basis of full complex-RNA assembly not solved"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0042393","term_label":"histone binding","supporting_discovery_ids":[1,2,3]},{"term_id":"GO:0003677","term_label":"DNA binding","supporting_discovery_ids":[1]},{"term_id":"GO:0003723","term_label":"RNA binding","supporting_discovery_ids":[4]},{"term_id":"GO:0140110","term_label":"transcription regulator activity","supporting_discovery_ids":[6,8]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[5]}],"localization":[{"term_id":"GO:0005694","term_label":"chromosome","supporting_discovery_ids":[0,2]},{"term_id":"GO:0000228","term_label":"nuclear chromosome","supporting_discovery_ids":[5,6]},{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[7]}],"pathway":[{"term_id":"R-HSA-4839726","term_label":"Chromatin organization","supporting_discovery_ids":[0,2,5]},{"term_id":"R-HSA-74160","term_label":"Gene expression (Transcription)","supporting_discovery_ids":[6,8]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[7]}],"complexes":["MSL dosage compensation complex"],"partners":["MSL1","MOF","RPD3","ROX2"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q8N5Y2","full_name":"MSL complex subunit 3","aliases":["Male-specific lethal 3 homolog","Male-specific lethal-3 homolog 1","Male-specific lethal-3 protein-like 1","MSL3-like 1"],"length_aa":521,"mass_kda":59.8,"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:20018852, PubMed:20657587, PubMed:20943666, PubMed:21217699, PubMed:30224647, 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). Acts as a histone reader that specifically recognizes and binds histone H4 monomethylated at 'Lys-20' (H4K20Me1) in a DNA-dependent manner and is proposed to be involved in chromosomal targeting of the MSL complex (PubMed:20657587, PubMed:20943666). May play a role X inactivation in females (PubMed:21217699)","subcellular_location":"Nucleus","url":"https://www.uniprot.org/uniprotkb/Q8N5Y2/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/MSL3","classification":"Not Classified","n_dependent_lines":9,"n_total_lines":1208,"dependency_fraction":0.0074503311258278145},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"HIST2H2BE","stoichiometry":0.2},{"gene":"POLR2I","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/MSL3","total_profiled":1310},"omim":[{"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":"609912","title":"LYSINE ACETYLTRANSFERASE 8; KAT8","url":"https://www.omim.org/entry/609912"},{"mim_id":"607303","title":"MORTALITY FACTOR 4-LIKE PROTEIN 1; MORF4L1","url":"https://www.omim.org/entry/607303"},{"mim_id":"301032","title":"BASILICATA-AKHTAR SYNDROME; MRXSBA","url":"https://www.omim.org/entry/301032"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Nucleoplasm","reliability":"Approved"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/MSL3"},"hgnc":{"alias_symbol":[],"prev_symbol":["MSL3L1"]},"alphafold":{"accession":"Q8N5Y2","domains":[{"cath_id":"2.30.30.140","chopping":"14-113","consensus_level":"high","plddt":85.5155,"start":14,"end":113},{"cath_id":"1.10.274.30","chopping":"177-226_245-292_420-513","consensus_level":"high","plddt":89.7123,"start":177,"end":513}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8N5Y2","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q8N5Y2-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q8N5Y2-F1-predicted_aligned_error_v6.png","plddt_mean":68.44},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=MSL3","jax_strain_url":"https://www.jax.org/strain/search?query=MSL3"},"sequence":{"accession":"Q8N5Y2","fasta_url":"https://rest.uniprot.org/uniprotkb/Q8N5Y2.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q8N5Y2/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8N5Y2"}},"corpus_meta":[{"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":"19029895","id":"PMC_19029895","title":"The MSL3 chromodomain directs a key targeting step for dosage compensation of the Drosophila melanogaster X chromosome.","date":"2008","source":"Nature structural & molecular biology","url":"https://pubmed.ncbi.nlm.nih.gov/19029895","citation_count":93,"is_preprint":false},{"pmid":"20657587","id":"PMC_20657587","title":"Corecognition of DNA and a methylated histone tail by the MSL3 chromodomain.","date":"2010","source":"Nature structural & molecular biology","url":"https://pubmed.ncbi.nlm.nih.gov/20657587","citation_count":81,"is_preprint":false},{"pmid":"12207710","id":"PMC_12207710","title":"Disruption of msl3 abolishes the synthesis of mycolipanoic and mycolipenic acids required for polyacyltrehalose synthesis in Mycobacterium tuberculosis H37Rv and causes cell aggregation.","date":"2002","source":"Molecular microbiology","url":"https://pubmed.ncbi.nlm.nih.gov/12207710","citation_count":72,"is_preprint":false},{"pmid":"12769850","id":"PMC_12769850","title":"MOF-regulated acetylation of MSL-3 in the Drosophila dosage compensation complex.","date":"2003","source":"Molecular cell","url":"https://pubmed.ncbi.nlm.nih.gov/12769850","citation_count":66,"is_preprint":false},{"pmid":"15988010","id":"PMC_15988010","title":"The MRG domain mediates the functional integration of MSL3 into the dosage compensation complex.","date":"2005","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/15988010","citation_count":48,"is_preprint":false},{"pmid":"20943666","id":"PMC_20943666","title":"Structural and biochemical studies on the chromo-barrel domain of male specific lethal 3 (MSL3) reveal a binding preference for mono- or dimethyllysine 20 on histone H4.","date":"2010","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/20943666","citation_count":37,"is_preprint":false},{"pmid":"30224647","id":"PMC_30224647","title":"De novo mutations in MSL3 cause an X-linked syndrome marked by impaired histone H4 lysine 16 acetylation.","date":"2018","source":"Nature genetics","url":"https://pubmed.ncbi.nlm.nih.gov/30224647","citation_count":33,"is_preprint":false},{"pmid":"16547465","id":"PMC_16547465","title":"X-chromosome targeting and dosage compensation are mediated by distinct domains in MSL-3.","date":"2006","source":"EMBO reports","url":"https://pubmed.ncbi.nlm.nih.gov/16547465","citation_count":32,"is_preprint":false},{"pmid":"10395802","id":"PMC_10395802","title":"Characterization of a novel chromo domain gene in xp22.3 with homology to Drosophila msl-3.","date":"1999","source":"Genomics","url":"https://pubmed.ncbi.nlm.nih.gov/10395802","citation_count":26,"is_preprint":false},{"pmid":"34878097","id":"PMC_34878097","title":"Msl3 promotes germline stem cell differentiation in female Drosophila.","date":"2022","source":"Development (Cambridge, England)","url":"https://pubmed.ncbi.nlm.nih.gov/34878097","citation_count":24,"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":"37847071","id":"PMC_37847071","title":"Loss of function of male-specific lethal 3 (Msl3) does not affect spermatogenesis in rodents.","date":"2023","source":"Developmental dynamics : an official publication of the American Association of Anatomists","url":"https://pubmed.ncbi.nlm.nih.gov/37847071","citation_count":2,"is_preprint":false},{"pmid":"40767387","id":"PMC_40767387","title":"Prolonged Follow-Up in a 30-Year-Old Male With a Novel Pathogenic Variant in MSL3 : A Case Report and a Brief Review of the Literature.","date":"2025","source":"American journal of medical genetics. Part A","url":"https://pubmed.ncbi.nlm.nih.gov/40767387","citation_count":1,"is_preprint":false},{"pmid":"36993289","id":"PMC_36993289","title":"Loss Of Chromodomain of Male-Specific Lethal 3 (MSL3) Does Not Affect Spermatogenesis In Rodents.","date":"2023","source":"bioRxiv : the preprint server for biology","url":"https://pubmed.ncbi.nlm.nih.gov/36993289","citation_count":0,"is_preprint":false},{"pmid":"41216464","id":"PMC_41216464","title":"Two Chinese patients with Basilicata-Akhtar syndrome caused by novel MSL3 variants: a case report and literature review.","date":"2025","source":"Translational pediatrics","url":"https://pubmed.ncbi.nlm.nih.gov/41216464","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":8980,"output_tokens":2775,"usd":0.034283,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":10081,"output_tokens":3686,"usd":0.071277,"stage2_stop_reason":"end_turn"},"total_usd":0.10556,"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\": 2011,\n      \"finding\": \"MSL1 acts as a scaffold for MSL complex assembly: it recruits MSL3 via an extended hydrophobic chain interface and MOF (HAT domain) via electrostatic interactions with a long MSL1 helix. Disruption of these interactions severely impairs MSL1 targeting to the body of dosage-compensated genes and several high-affinity sites, without affecting promoter binding.\",\n      \"method\": \"X-ray crystallography of binary MSL1-MSL3 and MSL1-MOF complexes, combined with selective point mutagenesis and ChIP analysis in Drosophila\",\n      \"journal\": \"Nature structural & molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structures with mutagenesis validated by in vivo ChIP; multiple orthogonal methods in a single rigorous study\",\n      \"pmids\": [\"21217699\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"The MSL3 chromodomain co-recognizes DNA and the H4K20 monomethyl mark: the DNA minor groove accommodates the histone H4 tail, and monomethyllysine inserts into a four-residue aromatic cage in MSL3. H4K16 acetylation antagonizes this MSL3 binding, suggesting MSL spreading is regulated by a combination of post-translational modifications.\",\n      \"method\": \"X-ray crystal structure of a ternary MSL3 chromodomain–DNA–H4K20me1 peptide complex; in vitro binding assays\",\n      \"journal\": \"Nature structural & molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — atomic-resolution ternary crystal structure with biochemical binding validation in a single rigorous study\",\n      \"pmids\": [\"20657587\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"The MSL3 chromodomain is required for the second targeting step of dosage compensation (spreading from chromatin entry sites to active gene bodies marked by H3K36me3): chromodomain mutants retain binding to entry sites but lose spreading, and show reduced preferential affinity for H3K36me3-containing nucleosomes in vitro.\",\n      \"method\": \"ChIP-chip analysis of MSL3 chromodomain mutants in Drosophila; in vitro nucleosome-binding assays with H3K36me3 nucleosomes\",\n      \"journal\": \"Nature structural & molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal in vivo (ChIP-chip) and in vitro (nucleosome binding) evidence; multiple orthogonal methods\",\n      \"pmids\": [\"19029895\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"The human MSL3 chromo-barrel domain binds preferentially to H4K20me1 and H4K20me2 peptides via an aromatic cage (Tyr-31, Phe-56, Trp-59, Trp-63). Mutation of Tyr-31 weakens H4K20me1 binding in vitro and compromises male survival in Drosophila, linking the methyllysine-binding cage to MSL complex chromatin targeting.\",\n      \"method\": \"X-ray crystallography of human MSL3 chromo-barrel domain (2.5 Å); in vitro peptide-binding assays; Drosophila male viability rescue assays with point mutants\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure combined with mutagenesis and in vitro binding, validated in vivo in Drosophila\",\n      \"pmids\": [\"20943666\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"MOF acetylates MSL-3 at a single lysine residue adjacent to its chromodomain; this acetylation regulates MSL-3's interaction with roX2 RNA and its localization to the X chromosome. RPD3 deacetylase complex interacts with MSL-3 and can reverse this acetylation, suggesting a regulated acetylation–deacetylation cycle controls DCC spreading.\",\n      \"method\": \"RNAi knockdown of individual DCC components; mass spectrometry identification of acetylation site; co-immunoprecipitation of RPD3 with MSL-3; RNA-binding and localization assays\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — MS-identified modification site, Co-IP of writer (MOF) and eraser (RPD3), functional RNA-binding and localization readouts; multiple orthogonal methods\",\n      \"pmids\": [\"12769850\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"The C-terminal MRG domain of MSL3 forms an integrated domain required for interaction with MSL1, and this interaction mediates activation of MOF's nucleosomal histone acetyltransferase activity in vitro and targeting of MSL3 to the X-chromosomal territory in vivo. Nucleic acid binding determinants reside separately in the N-terminus and are dispensable for DCC assembly.\",\n      \"method\": \"Domain deletion analysis; in vitro HAT activity assays; immunofluorescence localization in Drosophila cells\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — domain mutagenesis combined with in vitro enzymatic assay and in vivo localization; multiple orthogonal methods, replicated MSL1 interaction theme\",\n      \"pmids\": [\"15988010\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"MSL-3 targeting to the X chromosome (mediated by the MRG domain) and transcriptional upregulation of X-linked genes (requiring the chromo-barrel domain and polar region) are two functionally separable activities of MSL-3.\",\n      \"method\": \"Domain truncation/deletion mutants assayed by immunofluorescence for X-chromosome localization and quantitative RT-PCR for X-linked gene expression; viability assays in Drosophila\",\n      \"journal\": \"EMBO reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean domain-separation experiment in vivo, single lab, two readouts (localization + transcription)\",\n      \"pmids\": [\"16547465\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Pathogenic MSL3 variants in humans disrupt MSL complex assembly and activity, causing a pronounced loss of bulk H4K16ac in vivo and global transcriptome alterations. HDAC inhibitor treatment can partially rebalance acetylation and alleviate molecular/cellular phenotypes in patient-derived cells.\",\n      \"method\": \"Patient-derived cell lines; western blot for H4K16ac; MSL complex co-immunoprecipitation; RNA-seq; HDAC inhibitor rescue experiments\",\n      \"journal\": \"Nature genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (Co-IP, chromatin mark quantification, transcriptomics, pharmacological rescue) in patient cells; published in high-tier journal\",\n      \"pmids\": [\"30224647\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"In Drosophila female germline, Msl3 acts independently of the rest of the MSL complex to read H3K36me3 (deposited by Set2) and, together with the ATAC histone acetyltransferase complex, promotes transcription of genes including RpS19b; RpS19b upregulation is required for translation of Rbfox1, a meiotic cell cycle entry factor, thereby regulating germline stem cell differentiation.\",\n      \"method\": \"Genetic epistasis (msl3, set2, ATAC mutants); RNA-seq; ribosome profiling/translation assays; immunofluorescence in Drosophila ovaries\",\n      \"journal\": \"Development (Cambridge, England)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis with defined molecular pathway, single lab, multiple readouts (transcription + translation)\",\n      \"pmids\": [\"34878097\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"A human gene (MSL3L1, now MSL3) was identified encoding a protein with homology to Drosophila MSL-3 in three regions including two putative chromo domains, mapping to Xp22.3.\",\n      \"method\": \"Database homology search; genomic mapping; sequence analysis\",\n      \"journal\": \"Genomics\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 4 / Weak — computational/sequence-based identification only; no functional experiments performed on the human protein\",\n      \"pmids\": [\"10395802\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Conditional loss of Msl3 (chromodomain-disrupting allele) in mouse spermatogonia does NOT cause spermatogenesis defects or changes in expression of meiosis-related genes, indicating that MSL3 chromodomain function is dispensable for meiotic entry in rodents.\",\n      \"method\": \"Stra8-iCre conditional knockout mouse; histology; single-cell RNA-seq analysis\",\n      \"journal\": \"Developmental dynamics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean conditional KO with defined cellular readout; negative result robustly established in vivo\",\n      \"pmids\": [\"37847071\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"MSL3 is a chromatin-associated subunit of the MSL dosage compensation complex whose chromo-barrel domain binds H4K20me1/me2 and H3K36me3 on active chromatin to direct spreading of the complex along the X chromosome, while its C-terminal MRG domain docks onto MSL1 (the complex scaffold) to activate MOF's nucleosomal H4K16 acetyltransferase activity; MOF in turn acetylates MSL3 itself at a single lysine adjacent to its chromodomain—an acetylation reversed by RPD3—to regulate roX RNA binding and X-chromosomal localization, and pathogenic human MSL3 variants that disrupt complex assembly reduce bulk H4K16ac and cause the Basilicata-Akhtar neurodevelopmental syndrome.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"MSL3 is a chromatin-reader subunit of the MSL dosage compensation complex that couples recognition of active-chromatin histone marks to spreading of the complex and H4K16 acetylation along the X chromosome [#0, #2]. Its N-terminal chromo-barrel domain engages methylated histone tails through a four-residue aromatic cage, binding H4K20me1/me2 and co-recognizing DNA, while H4K16 acetylation antagonizes this engagement, providing a modification-sensitive switch for complex spreading [#1, #3]; the same domain confers preferential affinity for H3K36me3 nucleosomes and is required for the second targeting step that moves the complex from chromatin entry sites into transcribed gene bodies [#2]. The C-terminal MRG domain docks onto the MSL1 scaffold, and this contact both targets MSL3 to the X-chromosomal territory and activates MOF's nucleosomal H4K16 acetyltransferase activity, with X-targeting and transcriptional activation being functionally separable activities of the protein [#0, #5, #6]. MSL3 is itself acetylated by MOF at a single lysine adjacent to its chromodomain and deacetylated by the RPD3 complex, an acetylation-deacetylation cycle that tunes roX2 RNA binding and X-chromosomal localization [#4]. Beyond canonical dosage compensation, MSL3 reads H3K36me3 independently of the complex to promote ATAC-dependent transcription during Drosophila germline stem cell differentiation [#8]. Pathogenic human MSL3 variants disrupt complex assembly, reduce bulk H4K16ac, and cause the Basilicata-Akhtar neurodevelopmental syndrome, with HDAC inhibition partially rebalancing acetylation in patient cells [#7].\",\n  \"teleology\": [\n    {\n      \"year\": 1999,\n      \"claim\": \"Establishing a human ortholog of Drosophila MSL-3 was the first step toward asking whether dosage-compensation machinery is conserved in humans.\",\n      \"evidence\": \"database homology search and genomic mapping of MSL3L1 to Xp22.3\",\n      \"pmids\": [\"10395802\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"computational identification only; no functional experiments on the human protein\",\n        \"chromo-domain binding specificity not tested\",\n        \"complex membership not demonstrated\"\n      ]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Identifying MSL-3 as an acetylation substrate of MOF revealed that the reader is itself regulated by a writer-eraser cycle controlling its RNA binding and X localization.\",\n      \"evidence\": \"RNAi of DCC components, MS mapping of the acetylation site, RPD3 co-IP, and roX2 RNA-binding/localization assays in Drosophila\",\n      \"pmids\": [\"12769850\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"structural basis of how acetylation alters roX2 binding not resolved\",\n        \"in vivo kinetics of the acetylation-deacetylation cycle unknown\"\n      ]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Mapping the MRG domain as the MSL1-binding module showed how MSL3 is physically integrated into the complex and stimulates MOF catalysis, separating assembly from nucleic-acid binding.\",\n      \"evidence\": \"domain deletion analysis, in vitro nucleosomal HAT assays, and immunofluorescence localization in Drosophila cells\",\n      \"pmids\": [\"15988010\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"atomic detail of the MRG-MSL1 interface not yet defined here\",\n        \"mechanism of MOF activation by the interaction not resolved\"\n      ]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Demonstrating that X-chromosome targeting (MRG) and transcriptional upregulation (chromo-barrel/polar region) are separable activities clarified that MSL3 contributes two distinct functions to dosage compensation.\",\n      \"evidence\": \"domain truncation mutants assayed by immunofluorescence, RT-PCR, and viability in Drosophila\",\n      \"pmids\": [\"16547465\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"single-lab domain-separation result\",\n        \"molecular basis of the polar region's contribution to activation unknown\"\n      ]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Assigning the chromodomain to the spreading step distinguished chromatin entry from propagation, showing the reader drives movement into H3K36me3-marked gene bodies.\",\n      \"evidence\": \"ChIP-chip of chromodomain mutants and in vitro H3K36me3 nucleosome-binding assays in Drosophila\",\n      \"pmids\": [\"19029895\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"relative contribution of H3K36me3 versus H4K20 marks to spreading not disentangled\",\n        \"structural basis of H3K36me3 recognition not solved here\"\n      ]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Atomic structures of the chromo-barrel domain defined the aromatic cage and showed dual recognition of DNA and methylated H4K20, with H4K16ac acting as an antagonistic switch.\",\n      \"evidence\": \"ternary MSL3 chromodomain-DNA-H4K20me1 crystal structure, human MSL3 chromo-barrel structure, peptide-binding assays, and Drosophila viability rescue with cage mutants\",\n      \"pmids\": [\"20657587\", \"20943666\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"in vivo hierarchy among H4K20me1/me2 and H3K36me3 as the operative spreading mark unresolved\",\n        \"how H4K16ac antagonism is integrated with productive acetylation during spreading not defined\"\n      ]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Crystal structures of MSL1 binary complexes established MSL1 as the scaffold that recruits both MSL3 and MOF, defining the assembly architecture required for targeting gene bodies.\",\n      \"evidence\": \"X-ray structures of MSL1-MSL3 and MSL1-MOF complexes with point mutagenesis and ChIP in Drosophila\",\n      \"pmids\": [\"21217699\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"full quaternary architecture with roX RNA not resolved\",\n        \"how scaffold contacts couple to MOF catalytic activation not fully defined\"\n      ]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Linking pathogenic human MSL3 variants to disrupted complex assembly, reduced H4K16ac, and a neurodevelopmental syndrome translated the Drosophila mechanism into human disease and a candidate therapeutic axis.\",\n      \"evidence\": \"patient-derived cells with H4K16ac western blot, MSL complex co-IP, RNA-seq, and HDAC inhibitor rescue\",\n      \"pmids\": [\"30224647\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"tissue- and neuron-specific consequences in patients not defined\",\n        \"long-term efficacy of HDAC inhibition not established\"\n      ]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Showing a complex-independent role for Msl3 in reading H3K36me3 with ATAC during germline differentiation expanded its function beyond canonical X dosage compensation.\",\n      \"evidence\": \"genetic epistasis (msl3, set2, ATAC), RNA-seq, ribosome profiling, and immunofluorescence in Drosophila ovaries\",\n      \"pmids\": [\"34878097\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"single-lab study in one tissue\",\n        \"direct biochemical demonstration of Msl3-ATAC association not shown\"\n      ]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"A negative result in mouse spermatogonia showed that MSL3 chromodomain function is dispensable for meiotic entry in rodents, indicating the germline role is not conserved as in flies.\",\n      \"evidence\": \"Stra8-iCre conditional chromodomain-disrupting knockout with histology and single-cell RNA-seq in mouse\",\n      \"pmids\": [\"37847071\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"non-chromodomain MSL3 functions in mouse germline not tested\",\n        \"compensatory redundancy not excluded\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How chromatin-mark reading, MSL3 autoacetylation, roX RNA binding, and MOF activation are integrated in real time to direct complex spreading remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"no integrated dynamic model coupling mark recognition to acetylation output\",\n        \"human MSL3 mechanism characterized mainly through disease variants rather than reconstitution\",\n        \"structural basis of full complex-RNA assembly not solved\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0042393\", \"supporting_discovery_ids\": [1, 2, 3]},\n      {\"term_id\": \"GO:0003677\", \"supporting_discovery_ids\": [1]},\n      {\"term_id\": \"GO:0003723\", \"supporting_discovery_ids\": [4]},\n      {\"term_id\": \"GO:0140110\", \"supporting_discovery_ids\": [6, 8]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [5]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005694\", \"supporting_discovery_ids\": [0, 2]},\n      {\"term_id\": \"GO:0000228\", \"supporting_discovery_ids\": [5, 6]},\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [7]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-4839726\", \"supporting_discovery_ids\": [0, 2, 5]},\n      {\"term_id\": \"R-HSA-74160\", \"supporting_discovery_ids\": [6, 8]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [7]}\n    ],\n    \"complexes\": [\n      \"MSL dosage compensation complex\"\n    ],\n    \"partners\": [\n      \"MSL1\",\n      \"MOF\",\n      \"RPD3\",\n      \"roX2\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":6,"faith_pct":100.0}}