The Swi2/Snf2 bromodomain is required for the displacement of SAGA and the octamer transfer of SAGA-acetylated nucleosomes.

Faculty of Medicine and Health Sciences, Department of Biochemistry, United Arab Emirates University, P. O. Box 17666, Al-Ain, United Arab Emirates. ahmedh@uaeu.ac.ae
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.
Mesh Terms:
Acetylation, Adenosine Triphosphatases, Chromatin, DNA-Binding Proteins, Gene Expression Regulation, Fungal, Nucleosomes, Promoter Regions, Genetic, Protein Structure, Tertiary, Saccharomyces cerevisiae, Saccharomyces cerevisiae Proteins, Trans-Activators, Transcription Factors
J. Biol. Chem. Jun. 30, 2006; 281(26);18126-34 [PUBMED:16648632]
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