FAbCEb

FAbCEb is a hypothetical multi-subunit protein complex proposed to regulate gene expression in eukaryotic cells. The name derives from its proposed subunits: FAbC and Eb, with subunits FAbC1–FAbC3 and Eb1–Eb2. The model envisions FAbCEb forming a core complex that associates with chromatin near promoters and acts as a transcriptional coactivator for RNA polymerase II.

Structure and composition: The complex is described as a heterodecamer with a central scaffold (FAbC subunits) and peripheral Eb subunits mediating interactions with chromatin modifiers and the transcription machinery. Predicted features include a DNA-facing core and flexible tails that engage histone acetyltransferases and remodelers. Evidence comes from co-immunoprecipitation, crosslinking, and structural studies.

Discovery and evidence: FAbCEb was proposed in proteomic and genomic studies, with computational predictions followed by biochemical validation. Chromatin immunoprecipitation shows enrichment at promoter and enhancer regions, and RNA polymerase II occupancy increases with FAbCEb presence. Disruption reduces transcription of a defined gene set.

Function and mechanism: It is described as coordinating chromatin accessibility and transcription initiation by binding promoter-proximal DNA, recruiting or stabilizing RNA Pol II, and interacting with histone modifiers to promote an open chromatin state. It may also influence elongation via associations with elongation factors.

Regulation and significance: Activity is proposed to be modulated by post-translational modifications affecting subunit interactions and nuclear localization. FAbCEb is presented as a model for understanding how multi-subunit transcription regulators coordinate chromatin remodeling with activation, with potential relevance to development and disease contexts where gene expression is altered.