The hSWI/SNF chromatin remodelling complex can be found in association with PRMT5:WDR77, enhancing its methyltransferase activity towards histone substrates. Histone H3 arginine-9 (H3R8) and histone H4 arginine-4 (H4R3) are the preferred methylation sites of hSWI/SNF-associated PRMT5 (Pal et al. 2004).
SWI/SNF complexes are a family of ATP-dependent chromatin remodelling complexes involved in the activation and repression of gene transcription. They generate nucleosomes with altered positions, nucleosomes with DNA loops and nucleosomes that are capable of exchanging histone dimers or octamers (Racki & Narlikar 2008).
The core of the hSWI/SNF complex contains SMARCA4 (BRG1/BAF190A) or SMARCA2 (hBrm/BAF190B), SMARCC1 (BAF155), SMARCC2 (BAF170) and SMARCB1 (INI1) plus a variable number of additional subunits (Wang et al. 1996, Phelan et al. 1999, Reisman et al. 2009). SMARCA4 or SMARCA2 are the catalytic ATPase subunits. SMARCC1 and SMARCC2 are 62% identical to each other at the protein level (Wang et al. 1996). Loss of the SMARCB1 subunit (SWI/SNF-related matrix associated actin dependent regulator of chromatin B1) is a recurrent genetic characteristic of malignant rhabdoid tumor (MRT), a rare and aggressive pediatric cancer (Versteege et al. 1998, Biegel et al.1999). SMARCB1 mouse knockouts cause early embryonic lethality; heterozygous loss predisposes mice to MRT-like tumors (Klochendler-Yeivin et al. 2000, Roberts et al. 2000, Guidi et al. 2001). Actin and actin-related proteins found in hSWI/SNF complexes and are believed to facilitate nuclear matrix association (Zhao et al. 1998, Rando et al. 2002).