CDY2A

Model 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.

Predicted Gene Ontology terms

1. 01

   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.

2. 02

   The 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.

3. 03

   From 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.

4. 04

   This 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.

5. 05

   Cellular 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.

6. 06

   Mechanistically, 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.

7. 07

   From 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.