MBD4-mediated glycosylase activity on a chromatin template is enhanced by acetylation.
The ability of the MBD4 glycosylase to excise a mismatched base from DNA has been assessed in vitro using DNA substrates with different extents of cytosine methylation, in the presence or absence of reconstituted nucleosomes. Despite the enhanced ability of MBD4 to bind to methylated cytosines, the efficiency of its glycosylase activity on T/G mismatches was slightly dependent on the extent of methylation of the DNA substrate. The reduction in activity caused by competitor DNA was likewise unaffected by the methylation status of the substrate or the competitor. Our results also show that MBD4 efficiently processed T/G mismatches within the nucleosome. Furthermore, the glycolytic activity of the enzyme was not affected by the positioning of the mismatch within the nucleosome. However, histone hyperacetylation facilitated the efficiency with which the bases were excised from the nucleosome templates, irrespective of the position of the mismatch relative to the pseudodyad axis of symmetry of the nucleosome.
Department of Biochemistry and Microbiology, University of Victoria, P.O. Box 3055, Victoria, BC, Canada V8W 3P6.
Toyotaka
T
Ishibashi
Kevin
K
So
Claire G
CG
Cupples
Juan
J
Ausió
D000107:Acetylation; D020137:Base Pair Mismatch; D001483:Base Sequence; D002843:Chromatin / Q000201:enzymology*; D018899:CpG Islands / Q000235:genetics; D045647:DNA Glycosylases / Q000378:metabolism*; D019175:DNA Methylation; D004706:Endodeoxyribonucleases / Q000737:chemistry / Q000378:metabolism*; D006147:Guanine; D006367:HeLa Cells; D006657:Histones / Q000378:metabolism; D006801:Humans; D051783:Methyl-CpG-Binding Protein 2 / Q000737:chemistry; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009707:Nucleosomes / Q000201:enzymology; D011485:Protein Binding; D017510:Protein Folding; D013379:Substrate Specificity; D013698:Templates, Genetic; D013941:Thymine
D002843:Chromatin; D006657:Histones; D051783:Methyl-CpG-Binding Protein 2; D009707:Nucleosomes; D006147:Guanine; D004706:Endodeoxyribonucleases; C118712:MBD4 protein, human; D045647:DNA Glycosylases; D013941:Thymine