SIN3 Homolog B (SIN3B)

The deduced 954-amino acid protein contains 4 paired amphipathic helix (PAH) domains and shares significant homology with yeast Sin3 and mouse Sin3a. The highest homology lies within the 4 PAH domains and between PAH3 and PAH4. Sin3a and Sin3b share less homology at their N termini.The deduced protein contains 1,130 amino acids and shares 90% identity with mouse Sin3b over 710 amino acids. RT-PCR detected high expression in all tissues examined.Sin3a and Sin3b formed ternary complexes in solution with Mad and Max , and the complex recognized the Mad-Max E box-binding site and repressed transcription of a reporter gene. They hypothesized that Mad-Max represses transcription by tethering the Sin3 proteins to DNA as corepressors.