SAP30 is a subunit of the histone deacetylase complex, and this domain is a zinc-finger. Solution of the structure shows a novel fold comprising two β-strands and two α-helices with the zinc organising centre showing remote resemblance to the treble clef motif. In silico analysis of the structure reveals a highly conserved surface dominated by basic residues. NMR-based analysis of potential ligands for the SAP30 Zn-finger motif indicate a strong preference for nucleic acid substrates. The zinc-finger of SAP30 probably functions as a double-stranded DNA-binding motif, thereby expanding the known functions of both SAP30 and the mammalian Sin3 co-repressor complex [].
Corepressor interacting with RBPJ 1 (CIR1, also known as recepin) interacts CBF1, which is a member of the CSL family of DNA binding factors, which mediate either transcriptional repression or transcriptional activation. CIR1 binds to histone deacetylase and to SAP30 and serves as a linker between CBF1 and the histone deacetylase complex []. It interacts with a variety of proteins, including Epstein-Barr virus RPMS1 []and the NKAP transcriptional repressor of notch signaling [].
Sin3a is a transcriptional repressor and a homologue of the SIN3 repressor from yeast. Sin3a associates with the strong repressive isoform of Mxi1, a helix-loop-helix leucone zipper that associates with Max to antagonize Myc oncogenic activities []. Unlike Mxi1 and Myc, expression of Sin3a does not vary during development []. Sin3a is a component of several complexes, including the REST-CoREST repressor complex [], the PER complex which maintains circadian rhythm []and the Sin3 HDAC complex []. Sin3a also interacts with FOXK1 to regulate cell cycle progression []. Sin3a has three PAH domains by which it interacts with HCFC1, REST and SAP30 [, ].
This entry represents a 45 residue conserved domain found at the N-terminal end CIR protein (CBF1-interacting co-repressor, also known as corepressor interacting with RBPJ 1). This domain can be found in the fungal CWC25 family members and mammlian LENG1 (leukocyte receptor cluster member 1) protein.CBF1 (centromere-binding factor 1) acts as a transcription factor that causes repression by binding specifically to GTGGGAA motifs in responsive promoters, and it requires CIR as a co-repressor. CIR binds to histone deacetylase and to SAP30 and serves as a linker between CBF1 and the histone deacetylase complex []. CIR also plays a role in alternative splicing []. Budding yeast Cwc25 is a pre-mRNA-splicing factor involved in pre-mRNA splicing [].
