MEIS3P2

Model 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.

Predicted Gene Ontology terms

1. 01

   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.

2. 02

   This 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.

3. 03

   From 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.

4. 04

   Cellular 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.

5. 05

   Mechanistically, 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.