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Description:
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The reversible process of histone acetylation and deacetylation is an important mechanism of epigenetic regulation in the control of gene expression and chromatin structure . In general , histone acetylation is related to gene activation , whereas histone deacetylation is associated with transcriptional gene silencing and maintenance of heterochromatin . A large number of histone deacetylases (HDACs ) , the enzymes that catalyze the reaction of histone deacetylation , have been identified in plants and other eukaryotes , and they were found to play crucial roles in plant growth and development . In Arabidopsis thaliana , histone deacetylase 1 (AtHD1 ) is a homolog of Saccharomyces cerevisiae Rpd3 that is a global transcriptional regulator . Downregulation of AtHD1 in transgenic Arabidopsis results in histone hyperacetylation and induces a variety of phenotypic and developmental defects , suggesting that AtHD1 is also a global regulator of many physiological and developmental processes . To characterize the expression pattern and distribution of AtHD1 in cells , the subcellular location of AtHD1 was determined by monitoring the expression of an AtHD1 -GFP fusion protein in a transient expression assay and in transgenic Arabidopsis .The results show that AtHD1 is localized in the nucleus and appears to be excluded from the nucleolus . The histone deacetylase activity of AtHD1 was studied in an in vitro assay using radiolabeled histone peptides as a substrate . Recombinant AtHD1 produced by bacteria demonstrated a moderate but significant HDAC activity , whereas that produced by the baculovirus expression system did not have activity . This suggests that AtHD1 may require other cofactors or association with other proteins , rather than post -translational modifications , in order to have full HDAC activity . To study the possible interactions of AtHD1 with other proteins , a recombinant AtHD1 protein with two units of c -myc epitope fused to its C -terminus was expressed in transgenic Arabidopsis . We attempted to isolate proteins interacting with AtHD1 by co -immunoprecipitation (Co -IP ) . However , in the first few trials of Co -IP , a lot of contaminating proteins were present in the eluent along with the recombinant AtHD1 -cmyc protein . Improvements in the experimental conditions are required for further investigation . |