Sin3containing

Sin3-containing complexes are multiprotein transcriptional corepressor assemblies that use Sin3 proteins (Sin3A or Sin3B) as central scaffolds. They recruit histone deacetylases, primarily HDAC1 and HDAC2, to chromatin, promoting deacetylation of histone tails and a more compact chromatin state that represses transcription. In vertebrates, two major Sin3-centered complexes exist, based on Sin3A or Sin3B, which share a core set of subunits but differ in accessory components that tailor their regulatory activities.

Core subunits typically include HDAC1/2 and histone-binding partners such as RBBP4 and RBBP7. Accessory factors described in various contexts include SAP18, SAP30 (and its paralog SAP30L), SDS3, and ARID4A/ARID4B, among others. The precise composition can vary with cell type and developmental stage, allowing context-dependent gene regulation.

Functionally, Sin3-containing complexes act as transcriptional repressors that regulate genes involved in development, differentiation, and cell cycle control. They are recruited to promoters by sequence-specific transcription factors and other chromatin-associated proteins, enabling targeted gene silencing. These complexes also participate in DNA damage responses and broader chromatin remodeling pathways.

Conservation and medical relevance are noted across eukaryotes, with dysregulation of Sin3A or Sin3B complexes linked to cancer and developmental disorders, highlighting their role in epigenetic gene regulation. Research on these complexes employs methods such as co-immunoprecipitation, affinity purification, mass spectrometry, and chromatin immunoprecipitation (ChIP) to characterize subunit composition and genomic occupancy.