InterPro domain: IPR003121

The SWI/SNF family of complexes, which are conserved from yeast to humans, are ATP-dependent chromatin-remodelling proteins that facilitate transcription activation [ 1 , 2 , 3 ]. The mammalian complexes are made up of 9-12 proteins called BAFs (BRG1-associated factors). The BAF60 family have at least three members: BAF60a, which is ubiquitous, BAF60b and BAF60c, which are expressed in muscle and pancreatic tissues, respectively. BAF60b is present in alternative forms of the SWI/SNF complex, including complex B (SWIB), which lacks BAF60a. The SWIB domain is a conserved region found within the BAF60b proteins [ 4 ], and can be found fused to the C terminus of DNA topoisomerase in Chlamydia. This domain is also found in the Saccharomyces cerevisiae SNF12 protein, the eukaryotic initiation factor 2 (eIF2) [ 5 ]and the Arabidopsis thaliana At1g31760 protein [ 6 ].

MDM2 is an oncoprotein that acts as a cellular inhibitor of the p53 tumour suppressor by binding to the transactivation domain of p53 and suppressing its ability to activate transcription [ 7 ]. p53 acts in response to DNA damage, inducing cell cycle arrest and apoptosis. Inactivation of p53 is a common occurrence in neoplastic transformations. The core of MDM2 folds into an open bundle of four helices, which is capped by two small 3-stranded beta-sheets. It consists of a duplication of two structural repeats. MDM2 has a deep hydrophobic cleft on which the p53 alpha-helix binds; p53 residues involved in transactivation are buried deep within the cleft of MDM2, thereby concealing the p53 transactivation domain.

The SWIB and MDM2 domains are homologous and share a common fold.

1. Characterization of SWI/SNF protein expression in human breast cancer cell lines and other malignancies. J. Cell. Physiol. 186, 136-45
2. SWI/SNF chromatin-remodeling factors: multiscale analyses and diverse functions. J. Biol. Chem. 287, 30897-905
3. Localization and interactions of Plasmodium falciparum SWIB/MDM2 homologues. Malar J 15, 32
4. The SWIB and the MDM2 domains are homologous and share a common fold. Bioinformatics 18, 626-30
5. Crystal Structure of the C-terminal Domain of Human eIF2D and Its Implications on Eukaryotic Translation Initiation. J Mol Biol 429, 2765-2771
6. The Mitochondrial DNA-Associated Protein SWIB5 Influences mtDNA Architecture and Homologous Recombination. Plant Cell 29, 1137-1156
7. Structure of the MDM2 oncoprotein bound to the p53 tumor suppressor transactivation domain. Science 274, 948-53