@article {2009|1779, title = {Role of nucleic acid binding in Sir3p-dependent interactions with chromatin fibers.}, journal = {Biochemistry}, volume = {48}, number = {2}, year = {2009}, month = {jan}, pages = {276{\textendash}288}, publisher = {Department of Biological Sciences and Cell Differentiation and Development Center, Marshall University, Huntington, West Virginia 25755, USA.}, abstract = {

Recent studies of the mechanisms involved in the regulation of gene expression in eukaryotic organisms depict a highly complex process requiring a coordinated rearrangement of numerous molecules to mediate DNA accessibility. Silencing in Saccharomyces cerevisiae involves the Sir family of proteins. Sir3p, originally described as repressing key areas of the yeast genome through interactions with the tails of histones H3 and H4, appears to have additional roles in that process, including involvement with a DNA binding component. Our in vitro studies focused on the characterization of Sir3p-nucleic acid interactions and their biological functions in Sir3p-mediated silencing using binding assays, EM imaging, and theoretical modeling. Our results suggest that the initial Sir3p recruitment is partially DNA-driven, highly cooperative, and dependent on nucleosomal features other than histone tails. The initial step appears to be rapidly followed by the spreading of silencing using linker DNA as a track.

}, doi = {10.1021/bi801705g}, author = {Nicholas L Adkins and Steve J McBryant and Cotteka N Johnson and Jennifer M Leidy and Christopher L Woodcock and Charles H Robert and Jeffrey C Hansen and Philippe T Georgel} } @article {2006|1935, title = {HDAC1 acetylation is linked to progressive modulation of steroid receptor-induced gene transcription.}, journal = {Mol. Cell}, volume = {22}, number = {5}, year = {2006}, month = {jun}, pages = {669{\textendash}679}, publisher = {Laboratory of Receptor Biology and Gene Expression, National Cancer Institute, National Institutes of Health, Building 41, B602, Bethesda, Maryland 20892, USA.}, abstract = {Although histone deacetylases (HDACs) are generally viewed as corepressors, we show that HDAC1 serves as a coactivator for the glucocorticoid receptor (GR). Furthermore, a subfraction of cellular HDAC1 is acetylated after association with the GR, and this acetylation event correlates with a decrease in promoter activity. HDAC1 in repressed chromatin is highly acetylated, while the deacetylase found on transcriptionally active chromatin manifests a low level of acetylation. Acetylation of purified HDAC1 inactivates its deacetylase activity, and mutation of the critical acetylation sites abrogates HDAC1 function in vivo. We propose that hormone activation of the receptor leads to progressive acetylation of HDAC1 in vivo, which in turn inhibits the deacetylase activity of the enzyme and prevents a deacetylation event that is required for promoter activation. These findings indicate that HDAC1 is required for the induction of some genes by the GR, and this activator function is dynamically modulated by acetylation.}, keywords = {Acetylation, Amino Acid Sequence, Animals, Binding Sites, Cell Cycle Proteins, Chromatin, Down-Regulation, genetics/metabolism, Hela Cells, Histone Acetyltransferases, Histone Deacetylases, Humans, immunology/metabolism, metabolism}, doi = {10.1016/j.molcel.2006.04.019}, author = {Yi Qiu and Yingming Zhao and Matthias Becker and Sam John and Bhavin S Parekh and Suming Huang and Anindya Hendarwanto and Elisabeth D Martinez and Yue Chen and Hanxin Lu and Nicholas L Adkins and Diana A Stavreva and Malgorzata Wiench and Philippe T Geor} } @article {2005|1775, title = {Chromatin remodeling complexes: ATP-dependent machines in action.}, journal = {Biochem. Cell Biol.}, volume = {83}, number = {4}, year = {2005}, month = {aug}, pages = {405{\textendash}417}, publisher = {Division of Biological Sciences, Marshall University, Huntington, WV 25755, USA.}, abstract = {Since the initial characterization of chromatin remodeling as an ATP-dependent process, many studies have given us insight into how nucleosome-remodeling complexes can affect various nuclear functions. However, the multistep DNA-histone remodeling process has not been completely elucidated. Although new studies are published on a nearly weekly basis, the nature and roles of interactions of the individual SWI/SNF- and ISWI-based remodeling complexes and DNA, core histones, and other chromatin-associated proteins are not fully understood. In addition, the potential changes associated with ATP recruitment and its subsequent hydrolysis have not been fully characterized. This review explores possible mechanisms by which chromatin-remodeling complexes are recruited to specific loci, use ATP hydrolysis to achieve actual remodeling through disruption of DNA-histone interactions, and are released from their chromatin template. We propose possible roles for ATP hydrolysis in a chromatin-release/target-scanning process that offer an alternative to or complement the often overlooked function of delivering the energy required for sliding or dislodging specific subsets of core histones.}, keywords = {Adenosine Triphosphatases, Adenosine Triphosphate, Animals, Chromatin, Gene Expression Regulation, genetics/metabolism, Humans, metabolism, Nucleosomes, Transcription Factors}, doi = {10.1139/o05-115}, author = {Cotteka N Johnson and Nicholas L Adkins and Philippe Georgel} }