{"uniprot":"A8K0S8","gene":"MEIS3P2","name":"Putative homeobox protein Meis3-like 2","organism":"Homo sapiens (Human)","status":"dark","length":358,"sequence":"MARRYDELPHYPSIADGPAALAGFPEAVPAAPGPYGPHRPPQPLPPGLDSDGLKRDKDEIYGHPLFPLLALVFEKCELATCSPRDGAGAGLGTPRGGDVCSSDSFNEDNTAFAKQVRSERPFFSSNPELDNLMIQAIQVLRFHLLELEKGKMPIDLVIEDRDGGCREDFEDYPASCLSLPDQNNIWIRDHEDSGSVHLGTPGPSSGGLASQSGDNSSDQGVGLDTSVASPSSGGEDEDLDQEPRRNKKRGIFPKVATNIMRAWLFQHLWHPYPSEEQKKQLVQDTGLTILQVNNWFINARRRMVQPMIDQSNRIGQGAAFSPEGQPIGGYTETEPHVAFRPPASVGMSLNLEGEWHYL","function_summary":"A nuclear transcriptional regulator that combines an N-terminal interaction platform with a C-terminal DNA-binding module to control gene expression programs. It binds specific genomic sites via a homeodomain and recruits partner proteins to assemble repressive transcriptional complexes, thereby attenuating RNA polymerase II-driven transcription within the nucleoplasm and shaping developmental and differentiation pathways.","plain_language":"MEIS3P2 has barely been studied. The model's best guess: A nuclear transcriptional regulator that combines an N-terminal interaction platform with a C-terminal DNA-binding module to control gene expression programs. It binds specific genomic sites via a homeodomain and recruits partner proteins to assemble repressive transcriptional complexes, thereby attenuating RNA polymerase II-driven transcription within the nucleoplasm and shaping developmental and differentiation pathways.","uniprot_summary":"Transcriptional regulator.","go_terms":{"molecular_function":[{"id":"GO:0005515","label":"protein binding"},{"id":"GO:1990837","label":"sequence-specific double-stranded DNA binding"}],"biological_process":[{"id":"GO:0000122","label":"negative regulation of transcription by RNA polymerase II"}],"cellular_component":[{"id":"GO:0005654","label":"nucleoplasm"}]},"interpro":[{"id":"IPR009057","name":"Homeodomain-like superfamily","type":"homologous_superfamily","start":245,"end":317},{"id":"IPR032453","name":"Homeobox protein PKNOX/Meis, N-terminal","type":"domain","start":53,"end":150},{"id":"IPR001356","name":"Homeodomain","type":"domain","start":243,"end":310},{"id":"IPR008422","name":"KN homeodomain","type":"domain","start":263,"end":302}],"reasoning":"I begin with the InterPro architecture. The N-terminus carries IPR032453 (Homeobox protein PKNOX/Meis, N-terminal domain, residues 53–150), a hallmark module of the PKNOX/MEIS class that mediates selective protein–protein interactions and transcriptional complex assembly. The central-to-C-terminal region is dominated by DNA-binding modules: IPR001356 (Homeodomain, residues 243–310) and IPR008422 (KN homeodomain, residues 263–302), both embedded within IPR009057 (Homeodomain-like superfamily, residues 245–317). This ordered layout—an N-terminal PKNOX/MEIS interaction platform followed by a C-terminal KN-type homeodomain—creates a bipartite transcription factor: the N-terminus recruits cofactors and partner transcription factors, while the C-terminal homeodomain confers high-affinity, sequence-specific binding to double-stranded DNA.\n\nThis architecture dictates molecular function. The KN-type homeodomain (IPR008422) and canonical homeodomain (IPR001356) impose sequence-specific recognition of double-stranded DNA, aligning with GO:1990837 sequence-specific double-stranded DNA binding. The PKNOX/MEIS N-terminal domain (IPR032453) is optimized for assembling multi-protein transcriptional assemblies, supporting GO:0005515 protein binding. Together, these modules cause the protein to act as a DNA-anchored scaffold that recruits regulatory partners and modulates transcriptional output.\n\nFrom function to process, a homeodomain transcription factor typically modulates RNA polymerase II-driven gene expression. The presence of a strong interaction platform (IPR032453) coupled to a DNA-anchoring homeodomain enables assembly of corepressor complexes that attenuate transcriptional initiation or elongation. This mechanistic arrangement explains participation in GO:0000122 negative regulation of transcription by RNA polymerase II. Such repression can be context-dependent: the N-terminal domain selects cofactors, while the KN homeodomain positions the complex on target promoters or enhancers.\n\nCellular location follows directly. A DNA-binding homeodomain transcription factor operates in the nucleus, and the soluble, non-membranous nature of these domains places the protein in the nuclear interior where chromatin and transcriptional machinery reside. This supports localization to the GO:0005654 nucleoplasm and is consistent with a nuclear residence.\n\nMechanistically, I hypothesize that the N-terminal PKNOX/MEIS domain nucleates assemblies with TALE-class homeodomain partners and corepressors, while the KN homeodomain anchors the complex to specific genomic sites. Likely partners include PBX/MEIS family members that stabilize cooperative DNA binding, and chromatin-modifying enzymes that enforce repression. Through this assembly, the protein fine-tunes developmental and differentiation programs by dampening RNA polymerase II output at selected loci.","category":"dark","control_evaluation":null,"validation_plan":null,"structure":{"source":"AlphaFold DB","pdb":"/structures/AF-A8K0S8.pdb","alphafold":"https://alphafold.ebi.ac.uk/entry/A8K0S8"},"links":{"uniprot":"https://www.uniprot.org/uniprotkb/A8K0S8/entry","atlas":"/p/A8K0S8"},"provenance":{"model":"BioReason-Pro (ESM3 esm3-sm-open-v1)","source_list":"Pharos Tdark","note":"AI prediction, not experimentally verified"}}