SIN3AB

SIN3AB refers to the SIN3A/SIN3B family of large nuclear transcriptional co-repressors that serve as scaffolding subunits for histone deacetylase (HDAC) complexes in eukaryotic cells. The two closely related paralogs, SIN3A and SIN3B, encode proteins with shared domain architecture that enables them to assemble multi-subunit chromatin-modifying complexes. As core components, they recruit HDAC1/2 and a set of accessory proteins to targeted gene promoters and enhancers, promoting chromatin condensation and transcriptional repression.

Structure and interactions are centered on conserved regions that mediate protein–protein contacts. Through these interactions, SIN3A and SIN3B coordinate the assembly of a repressive complex that includes HDACs and other chromatin-modifying factors, allowing precise control of gene expression programs during development, differentiation, and cell cycle progression. Although highly related, SIN3A and SIN3B can exhibit overlapping as well as distinct expression patterns and functional roles in different tissues and developmental stages.

Functionally, SIN3A/B act as transcriptional co-repressors by directing histone deacetylation and chromatin remodeling at target loci. They are recruited by sequence-specific transcription factors and chromatin-associated proteins, enabling repression of diverse gene sets involved in proliferation, differentiation, and stress responses. Beyond repression, SIN3A/B participate in broader regulatory networks influencing DNA damage response and pluripotency in certain cellular contexts.

In development and disease, SIN3A is generally essential for embryonic viability in model organisms, while SIN3B contributes to tissue- and context-specific repression. Misregulation of SIN3A/B activity has been linked to cancer and developmental disorders, reflecting their central role in chromatin-based gene regulation. The term SIN3AB is sometimes used to denote the broader SIN3A/SIN3B functional family when studies address both paralogs.