Catalog Number:
(89359-220)
Clearance
Supplier:
Genetex
Description:
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. The SWI/SNF complex was originally identified in yeast as a 2 MDa complex, later shown to be highly conserved in all eukaryotes. Components of the hSWI/SNF complexes have been implicated in a range of cellular events including gene activation, regulation of cell growth, and development. The human homologue of yeast SNF5, SMARCB1, was identified in a two-hybrid screening performed to identify binding targets of the integrase of HIV, and the gene called INI1. Many studies have indicated that yeast SNF and its human counterparts are able to interact with sequence-specific transcription factors, which may recruit the complex to specific genes. For example, it has been shown that SMARCB1 interacts with the protooncogene c-Myc and the SWI complex is necessary for c-Myc mediated transactivation. Mutations in SNF5 and Brg1, both SWI components, suggest a connection of the complex with cancer. In fact, SMARCB1 displays properties of a tumor-suppressor gene, as sporadic rhabdoid tumors show biallelic loss-of-function mutations, and germline mutations confer and autosomal-dominant syndrome that predisposes patients to a variety of rhabdoid cancers.
