InterPro domain: IPR042534

This superfamily includes several eukaryotic Sin3 associated polypeptide p18 (SAP18) sequences. SAP18 is known to be a component of the Sin3-containing complex which is responsible for the repression of transcription via the modification of histone polypeptides [ 1 ]. SAP18 (UBL domain) is one of the three three ASAP subunits (along with Acinus (beta-hairpin motif) and RNPS1 (RRM domain)) that play a role in programmed cell death, transcriptional regulation, pre-mRNA splicing and mRNA quality control [ 2 , 3 ]. The ASAP complex interacts with the exon-junction complex (EJC), a messenger ribonucleoprotein complex involved in post-transcriptional regulation [ 4 ].

The high degree of evolutionary conservation and the fortuitous crystal contacts at the alpha-beta groove suggest that this surface of SAP18 is a hot spot for interactions. Possible binding partners targeting this surface of SAP18 are transcription factors (such as Bicoid and Kruppel) and/or Sin3a-HDAC subunits.

1. Histone deacetylases and SAP18, a novel polypeptide, are components of a human Sin3 complex. Cell 89, 357-64
2. ASAP, a novel protein complex involved in RNA processing and apoptosis. Mol. Cell. Biol. 23, 2981-90
3. The structure of the ASAP core complex reveals the existence of a Pinin-containing PSAP complex. Nat. Struct. Mol. Biol. 19, 378-86