Abstract
BackgroundModifications of DNA and histones in various combinations are correlated with many cellular processes. In this study, we investigated the possible relationship between histone H4 tetraacetylation, DNA methylation and histone H3 dimethylation at lysine 9 during mitosis in maize root meristems.ResultsTreatment with trichostatin A, which inhibits histone deacetylases, resulted in increased histone H4 acetylation accompanied by the decondensation of interphase chromatin and a decrease in both global H3K9 dimethylation and DNA methylation during mitosis in maize root tip cells. These observations suggest that histone acetylation may affect DNA and histone methylation during mitosis. Treatment with 5-azacytidine, a cytosine analog that reduces DNA methylation, caused chromatin decondensation and mediated an increase in H4 acetylation, in addition to reduced DNA methylation and H3K9 dimethylation during interphase and mitosis. These results suggest that decreased DNA methylation causes a reduction in H3K9 dimethylation and an increase in H4 acetylation.ConclusionsThe interchangeable effects of 5-azacytidine and trichostatin A on H4 acetylation, DNA methylation and H3K9 dimethylation indicate a mutually reinforcing action between histone acetylation, DNA methylation and histone methylation with respect to chromatin modification. Treatment with trichostatin A and 5-azacytidine treatment caused a decrease in the mitotic index, suggesting that H4 deacetylation and DNA and H3K9 methylation may contain the necessary information for triggering mitosis in maize root tips.
Highlights
Modifications of DNA and histones in various combinations are correlated with many cellular processes
Trichostatin A (TSA) and 5-AC both affect H4 acetylation, H3K9 dimethylation and DNA methylation To assess the effects of TSA and 5-AC on levels of H4 tetraacetylation (H4ac) and H3K9me2, western blots were performed with anti-H4ac and anti-H3K9me2 antibodies
The results of the western blots showed that TSA caused a clear increase in global histone H4 acetylation (0.88 ± 0.03) in maize root tips compared with controls (0.68 ± 0.03)
Summary
Modifications of DNA and histones in various combinations are correlated with many cellular processes. The amino-terminal tails of these histones are subject to various post-translational modifications such as methylation, acetylation, phosphorylation, ubiquitination and ADP-ribosylation [3]. Various histone-modifying enzymes able to add or remove chromatin modifications, including histone acetyltransferases (HATs), histone deacetylases (HDACs) and lysine methyltransferases, have been identified [3]. HATs and HDACs have been found to alter global histone acetylation levels over large regions of chromatin [4]. DNA itself may be modified through the methylation of cytosine by DNA methyltransferase (DNMT) [5]. Histone and DNA modifications are dynamic and have wide-ranging and profound effects on many nuclear processes [6,7]
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