{"uniprot":"Q9Y6F7","gene":"CDY2A","name":"Testis-specific chromodomain protein Y 2","organism":"Homo sapiens (Human)","status":"dark","length":541,"sequence":"MASQEFEVEAIVDKRQDKNGNTQYLVRWKGYDKQDDTWEPEQHLMNCEKCVHDFNRRQTEKQKKLTWTTTSRIFSNNARRRTSRSTKANYSKNSPKTPVTDKHHRSKNCKLFAASKNVRRKAASTLSDTKNMEIINSTIETLAPDSPFDHKKTVSGFQKLEKLDPIAADQQDTVVFKVTEGKLLRDPLSHPGAEQTGIQNKTQMHPLMSQMSGSVTASMATGSATRKGIVVLIDPLAANGTTDMHTSVPRVKGGQRNITDDSRGQPFIKKMHFTIRLTESAITYRDIVVKKEDGFTQIVLSTRSTEKNALNTEVIKEMVNALNSAAADDSKLVLFSAAGSVFCCGLDFGYFVRHLRNDRNTASLEMVDTIKNFVNTFIQFKKPIVVSVNGPAIGLGASILPLCDLVWANEKAWFQTPYTTFGQSPDGCSSITFPKMMGKASANEMLIAGRKLTAREACAKGLVSQVFLTGTFTQEVMIQIKELASYNAIVLEECKALVRCNIKLELEQANERECEVLRKIWSSAQGIESMLKYVENKIDEF","function_summary":"A nuclear chromatin-associated regulator that uses an N-terminal methyl-lysine–recognition module to anchor on modified nucleosomes and a C-terminal crotonase-like scaffold to assemble regulatory complexes. By coupling selective histone binding with higher-order assembly, it modulates transcriptional and chromatin states that underpin germline programs, thereby contributing to spermatogenic pathways in human cells.","plain_language":"CDY2A has barely been studied. The model's best guess: A nuclear chromatin-associated regulator that uses an N-terminal methyl-lysine–recognition module to anchor on modified nucleosomes and a C-terminal crotonase-like scaffold to assemble regulatory complexes. By coupling selective histone binding with higher-order assembly, it modulates transcriptional and chromatin states that underpin germline programs, thereby contributing to spermatogenic pathways in human cells.","uniprot_summary":"May be involved in transcriptional regulation or chromatin organization.","go_terms":{"molecular_function":[{"id":"GO:0042393","label":"histone binding"},{"id":"GO:0035064","label":"methylated histone binding"}],"biological_process":[{"id":"GO:0007283","label":"spermatogenesis"}],"cellular_component":[{"id":"GO:0005634","label":"nucleus"}]},"interpro":[{"id":"IPR016197","name":"Chromo-like domain superfamily","type":"homologous_superfamily","start":3,"end":63},{"id":"IPR029045","name":"ClpP/crotonase-like domain superfamily","type":"homologous_superfamily","start":282,"end":530},{"id":"IPR014748","name":"Enoyl-CoA hydratase, C-terminal","type":"homologous_superfamily","start":485,"end":541},{"id":"IPR017984","name":"Chromo domain subgroup","type":"domain","start":3,"end":11},{"id":"IPR000953","name":"Chromo/chromo shadow domain","type":"domain","start":5,"end":66},{"id":"IPR023780","name":"Chromo domain","type":"domain","start":6,"end":57},{"id":"IPR017984","name":"Chromo domain subgroup","type":"domain","start":17,"end":31},{"id":"IPR017984","name":"Chromo domain subgroup","type":"domain","start":32,"end":44},{"id":"IPR001753","name":"Enoyl-CoA hydratase/isomerase-like domain","type":"domain","start":295,"end":537},{"id":"IPR051053","name":"Enoyl-CoA hydratase/isomerase and chromodomain-containing protein","type":"family","start":12,"end":539},{"id":"IPR023779","name":"Chromo domain, conserved site","type":"conserved_site","start":24,"end":44}],"reasoning":"I begin by dissecting the InterPro architecture and its order along the sequence. The N-terminus (residues 3–66) is densely annotated with chromatin-reader signatures: IPR016197 (Chromo-like domain superfamily, residues 3–63), IPR017984 (Chromo domain subgroup, residues 3–11), IPR000953 (Chromo/chromo shadow domain, residues 5–66), IPR023780 (Chromo domain, residues 6–57), and IPR017984 (Chromo domain subgroup, residues 17–31 and 32–44), with a conserved chromo-site IPR023779 (Chromo domain, conserved site, residues 24–44). This tightly clustered chromodomain module establishes a methyl-lysine recognition platform that binds methylated histone tails and nucleosomes. Such chromodomains create high-affinity, modification-dependent contacts with chromatin, causally explaining histone binding and methylated histone binding as core molecular functions.\n\nThe C-terminal two-thirds of the protein is a crotonase/enoyl-CoA hydratase-like scaffold: IPR029045 (ClpP/crotonase-like domain superfamily, residues 282–530), IPR001753 (Enoyl-CoA hydratase/isomerase-like domain, residues 295–537), and IPR014748 (Enoyl-CoA hydratase, C-terminal, residues 485–541). This enzymatic-like fold is frequently repurposed in nuclear proteins as a rigid oligomerization and ligand-binding platform rather than a metabolic enzyme. Its presence, together with the chromodomain, is reinforced by IPR051053 (Enoyl-CoA hydratase/isomerase and chromodomain-containing protein family, residues 12–539), which explicitly couples these two modules into a single functional assembly. The N-to-C arrangement—an N-terminal chromatin-reader followed by a C-terminal crotonase-like scaffold—creates a bipartite architecture: chromatin targeting followed by assembly of effector complexes.\n\nFrom this architecture, I infer molecular function first. The N-terminal chromodomain suite (IPR016197, IPR017984, IPR000953, IPR023780, IPR023779) causes selective binding to methylated histones and nucleosomes, aligning with GO:0042393 histone binding and GO:0035064 methylated histone binding. The crotonase-like region does not supply catalytic chemistry here; instead it stabilizes higher-order assemblies and may contribute to nucleic acid or protein interfaces that tune chromatin-associated complexes.\n\nThis molecular function naturally extends to biological process. Chromodomain-mediated recognition of methylated histones positions the protein on specific chromatin states that regulate transcription and genome maintenance. In the male germline, extensive chromatin remodeling accompanies meiosis and spermiogenesis; a chromatin reader that assembles regulatory complexes is poised to influence spermatogenic transcriptional programs. This mechanistic role supports involvement in GO:0007283 spermatogenesis.\n\nCellular location follows directly from the chromatin-reader architecture and function. Chromodomains operate on nucleosomes; therefore the protein resides in the nucleus, consistent with GO:0005634 nucleus. The absence of transmembrane segments and the presence of chromatin-targeting motifs further constrain localization to the nuclear compartment.\n\nMechanistically, I hypothesize that the N-terminal chromodomain targets methylated histone marks and nucleosomes, anchoring the protein to specific genomic loci. The C-terminal crotonase-like scaffold then nucleates assemblies of transcriptional and chromatin-modifying factors, tuning gene expression and possibly stabilizing higher-order chromatin states. In spermatogenic cells, this architecture would modulate stage-specific transcription and chromatin transitions.\n\nFrom this model, likely interaction partners include nucleosomes and histone H3/H4 tails bearing methyl marks; chromatin-modifying complexes such as histone methyltransferase and deacetylase assemblies; and transcriptional regulators recruited to methylated chromatin. In the testis, associations with germline-specific chromatin remodelers and transcription factors would be favored to coordinate spermatogenesis programs.","category":"dark","control_evaluation":null,"validation_plan":null,"structure":{"source":"AlphaFold DB","pdb":"/structures/AF-Q9Y6F7.pdb","alphafold":"https://alphafold.ebi.ac.uk/entry/Q9Y6F7"},"links":{"uniprot":"https://www.uniprot.org/uniprotkb/Q9Y6F7/entry","atlas":"/p/Q9Y6F7"},"provenance":{"model":"BioReason-Pro (ESM3 esm3-sm-open-v1)","source_list":"Pharos Tdark","note":"AI prediction, not experimentally verified"}}