Effect of histone H3 E73D mutation on in vitro chromatin silencing
Date
2007
Authors
Colbert, Karen, author
Subramanian, Vidya, author
Thompson, Jeffrey, author
Luger, Karolin, author
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Abstract
Organization of DNA into chromatin requires the presence of small basic proteins called histones. Core histones are highly conserved across various species. In addition to their function as DNA packing material, histones play an important role in the regulation of transcription, replication, and gene silencing. In particular, histone-mediated silencing is achieved via histone modifications and through interactions with suppressor proteins. In the yeast Saccharomyces cerevisiae, a single amino acid substitution (E73D) found within the conserved region of histone H3, has been shown to de-repress silencing at the telomeres and mating type loci in yeast (Thompson et al., 2003). It has been proposed that the substitution may shorten the amino acid side chain length enough to disrupt a necessary interaction at the H3-H4 interface within the nucleosome. Alternatively, the E73D mutation may affect the binding affinity of Sir3 for histone H3. Sir3 and Sir4, chromatin-associated repressor proteins, are known to mediate telomeric and mating loci silencing in S. cerevisiae (Grunstein et al., 1997). In order to test the effect of the E73D mutation on nucleosome stability in vitro, the crystal structure of nucleosomes containing the H3 mutant will be determined to ascertain the charge interactions between the amino acid residues within the vicinity of the substituted residue. In addition, binding studies will be carried out to investigate Sir protein binding to nucleosomes containing H3 E73D histones. Finally, analytical ultracentrifugation experiments will provide quantitative data on the in vitro dynamics of nucleosomal arrays comprised of nucleosomes containing H3 E73D.
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Subject
histones
DNA