The SWI/SNF and SAGA chromatin-modifying complexes contain bromodomains that help anchor these complexes to acetylated promoter nucleosomes. To study the importance of bromodomains in these complexes, we have compared the chromatin-remodeling and octamer-transfer activity of the SWI/SNF complex to a mutant complex that lacks the Swi2/Snf2 bromodomain. Here we show that the SWI/SNF complex can remodel or transfer SAGA-acetylated nucleosomes more efficiently than the Swi2/Snf2 bromodomain-deleted complex. These results demonstrate that the Swi2/Snf2 bromodomain is important for the remodeling as well as for the octamer-transfer activity of the complex on H3-acetylated nucleosomes. Moreover, we show that, although the wild-type SWI/SNF complex displaces SAGA that is bound to acetylated nucleosomes, the bromodomain mutant SWI/SNF complex is less efficient in SAGA displacement. Thus, the Swi2/Snf2 bromodomain is required for the full functional activity of SWI/SNF on acetylated nucleosomes and is important for the displacement of SAGA from acetylated promoter nucleosomes.
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The Swi2/Snf2 bromodomain is important for the full binding and remodeling activity of the SWI/SNF complex on H3- and H4-acetylated nucleosomes.
Ann N Y Acad Sci
September 2008
Faculty of Medicine and Health Sciences, Department of Biochemistry, UAE University, Al Ain, United Arab Emirates.
The SWI/SNF chromatin-remodeling complex contains a bromodomain in its Swi2/Snf2 subunit that helps tether it to acetylated promoter nucleosomes. To study the importance of this bromodomain in the SWI/SNF complex, we have compared the nucleosome-binding and the chromatin-remodeling activities of the SWI/SNF to a mutant complex that lacks the Swi2/Snf2 bromodomain. Here we show that the SWI/SNF complex deleted of the Swi2/Snf2 bromodomain cannot bind to SAGA- or NuA4-acetylated nucleosomes as well as the wild-type complex.
View Article and Find Full Text PDFSelective recognition of acetylated histones by bromodomains in transcriptional co-activators.
Biochem J
February 2007
Department of Biochemistry, Faculty of Medicine and Health Sciences, UAE University, P.O. Box 17666, Al-Ain, United Arab Emirates.
Bromodomains are present in many chromatin-associated proteins such as the SWI/SNF and RSC chromatin remodelling and the SAGA HAT (histone acetyltransferase) complexes, and can bind to acetylated lysine residues in the N-terminal tails of the histones. Lysine acetylation is a histone modification that forms a stable epigenetic mark on chromatin for bromodomain-containing proteins to dock and in turn regulate gene expression. In order to better understand how bromodomains read the 'histone code' and interact with acetylated histones, we have tested the interactions of several bromodomains within transcriptional co-activators with differentially acetylated histone tail peptides and HAT-acetylated histones.
View Article and Find Full Text PDFSWI/SNF displaces SAGA-acetylated nucleosomes.
Eukaryot Cell
October 2006
Stowers Institute for Medical Research, 1000 E 50th St., Kansas City, MO 64110, USA.
SWI/SNF is a well-characterized chromatin remodeling complex that remodels chromatin by sliding nucleosomes in cis and/or displacing nucleosomes in trans. The latter mechanism has the potential to remove promoter nucleosomes, allowing access to transcription factors and RNA polymerase. In vivo, histone acetylation often precedes apparent nucleosome loss; therefore, we sought to determine whether nucleosomes containing acetylated histones could be displaced by the SWI/SNF chromatin remodeling complex.
View Article and Find Full Text PDFThe Swi2/Snf2 bromodomain is required for the displacement of SAGA and the octamer transfer of SAGA-acetylated nucleosomes.
J Biol Chem
June 2006
Faculty of Medicine and Health Sciences, Department of Biochemistry, United Arab Emirates University, P. O. Box 17666, Al-Ain, United Arab Emirates.
The SWI/SNF and SAGA chromatin-modifying complexes contain bromodomains that help anchor these complexes to acetylated promoter nucleosomes. To study the importance of bromodomains in these complexes, we have compared the chromatin-remodeling and octamer-transfer activity of the SWI/SNF complex to a mutant complex that lacks the Swi2/Snf2 bromodomain. Here we show that the SWI/SNF complex can remodel or transfer SAGA-acetylated nucleosomes more efficiently than the Swi2/Snf2 bromodomain-deleted complex.
View Article and Find Full Text PDFFunction and selectivity of bromodomains in anchoring chromatin-modifying complexes to promoter nucleosomes.
Cell
November 2002
Howard Hughes Medical Institute, Department of Biochemistry and Molecular Biology, The Pennsylvania State University, 306 Althouse Laboratory, University Park, PA 16802, USA.
The functions of the SAGA and SWI/SNF complexes are interrelated and can form stable "epigenetic marks" on promoters in vivo. Here we show that stable promoter occupancy by SWI/SNF and SAGA in the absence of transcription activators requires the bromodomains of the Swi2/Snf2 and Gcn5 subunits, respectively, and nucleosome acetylation. This acetylation can be brought about by either the SAGA or NuA4 HAT complexes.
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