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Structure of Arp7-Arp9-Snf2(HSA)-RTT102 subcomplex of SWI/SNF chromatin remodeler.
Structural highlights
FunctionARP7_YEAST Component of the chromatin structure remodeling complex (RSC), which is involved in transcription regulation and nucleosome positioning. RSC is responsible for the transfer of a histone octamer from a nucleosome core particle to naked DNA. The reaction requires ATP and involves an activated RSC-nucleosome intermediate. Remodeling reaction also involves DNA translocation, DNA twist and conformational change. As a reconfigurer of centromeric and flanking nucleosomes, RSC complex is required both for proper kinetochore function in chromosome segregation and, via a PKC1-dependent signaling pathway, for organization of the cellular cytoskeleton. This subunit is involved in transcriptional regulation. Heterodimer of ARP7 and ARP9 functions with HMG box proteins to facilitate proper chromatin architecture. Heterodimer formation is necessary for assembly into RSC complex. Part of the SWI/SNF complex, an ATP-dependent chromatin remodeling complex, is required for the positive and negative regulation of gene expression of a large number of genes. It changes chromatin structure by altering DNA-histone contacts within a nucleosome, leading eventually to a change in nucleosome position, thus facilitating or repressing binding of gene-specific transcription factors.[1] [2] [3] [4] [5] [6] [7] [8] Publication Abstract from PubMedThe packaging of DNA into nucleosomal structures limits access for templated processes such as transcription and DNA repair. The repositioning or ejection of nucleosomes is therefore critically important for regulated events, including gene expression. This activity is provided by chromatin remodeling complexes, or remodelers, which are typically large, multisubunit complexes that use an ATPase subunit to translocate the DNA. Many remodelers contain pairs or multimers of actin-related proteins (ARPs) that contact the helicase-SANT-associated (HSA) domain within the catalytic ATPase subunit and are thought to regulate ATPase activity. Here, we determined the structure of a four-protein subcomplex within the SWI/SNF remodeler that comprises the Snf2 HSA domain, Arp7, Arp9, and repressor of Ty1 transposition, gene 102 (Rtt102). Surprisingly, unlike characterized actin-actin associations, the two ARPs pack like spoons and straddle the HSA domain, which forms a 92-A-long helix. The ARP-HSA interactions are reminiscent of contacts between actin and many binding partners and are quite different from those in the Arp2/3 complex. Rtt102 wraps around one side of the complex in a highly extended conformation that contacts both ARPs and therefore stabilizes the complex, yet functions to reduce by approximately 2.4-fold the remodeling and ATPase activity of complexes containing the Snf2 ATPase domain. Thus, our structure provides a foundation for developing models of remodeler function, including mechanisms of coupling between ARPs and the ATPase translocation activity. Structure of an actin-related subcomplex of the SWI/SNF chromatin remodeler.,Schubert HL, Wittmeyer J, Kasten MM, Hinata K, Rawling DC, Heroux A, Cairns BR, Hill CP Proc Natl Acad Sci U S A. 2013 Feb 26;110(9):3345-50. doi:, 10.1073/pnas.1215379110. Epub 2013 Feb 11. PMID:23401505[9] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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