Chromatin, the physiological packaging structure of histone proteins and DNA, is considered a key element in regulating gene expression. Several complexes involved in transcriptional regulation function by either modifying histones or altering chromatin structure. Postranslational modifications of histones, such as acetylation, phosphorylation and methylation, contribute to the regulation of transcription. The ATP-dependent chromatin-remodeling complexes alter chromatin structure by using the energy of ATP hydrolysis to locally disrupt the association of histones with DNA, displacing the nucleosomes from promoter and enhancer regions, and therefore allowing transcription initiation. Chromatin remodeling complexes have been purified from a variety of organisms, and most cell types contain more than one type of complex. These complexes contain structurally related catalytic subunits, but differ in the way in which they manipulate chromatin. Three families of complexes have been described the SWI/SNF family, ISWI family, and Mi-2 family. The SWI/SNF family of ATP-dependent remodeling complexes was identified in yeast, drosophila, and human. It causes nucleosomes to change structure and/or position in order to allow transcriptional activators to gain access to their target sites. In humans, two conserved ATPase subunits have been identified as hBrm (also designated hSNF2alpha) and Brg1 (also designated as SNF2beta). Brg1 (1,613 amino acids) and hBrm (1,586 amino acids) share approximately 52% identity. Components of the hSWI/SNF complexes have been implicated in a range of cellular events including gene activation, regulation of cell growth, and development. Brg1 and hBrm enhances transcriptional activation by glucocorticoid receptors. Apparently, Brg1 and Brm complexes direct distinct cellular processes by recruitment to specific promoters through protein-protein interactions that are unique to each ATPase. The remodeling complexes were traditionally associated with transcriptional activation. However, SWI/SNF has been found associated with repressor complexes, such as HDAC (histone deacetylase) and Rb (retinoblastoma) in a complex that leads to cell cycle arrest, suggesting that they are associated with transcriptional repression. Antibodies reacting specifically with hBrm/SNF2alpha may be used for studying the effects of chromatin remodeling on gene expression.
IF: Use at a concentration of 1 μg/ml. WB: Use at a concentration of 0.15 μg/ml. Predicted molecular weight: 230 kDa. Staining of SMARCA2 is specifically inhibited by the immunizing peptide. Not tested in other applications. Optimal dilutions/concentrations should be determined by the end user.