title: Undermethylation of DNA in mononucleosomes solubilized by micrococcal nuclease digestion of HeLa cell nuclei.
abstract: To examine the distribution of 5-methylcytosine in chromatin DNA, DNA of HeLa cells was labeled with [3H-methyl]methionine and [14C] thymidine and analyzed after extensive digestion of the nuclei with micrococcal nuclease. When the chromatin solubilized with the nuclease was fractionated on a sucrose density gradient, DNA in mononucleosomes was considerably depleted in 5-methylcytosine, as compared with polynucleosomes. Electrophoretic separation of DNA from the chromatin also revealed the depletion of 5-methylcytosine in the mononucleosomal size of DNA. This was confirmed by the chromatographic analysis of 5-methyldeoxycytidine after enzymatic digestion of the DNA to nucleosides. Thus the DNA in mononucleosomes solubilized by extensive micrococcal nuclease digestion is depleted in 5-methylcytosine, suggesting that 5-methylcytosine is preferentially missing from the DNA in the nucleosome core particles.
mesh_terms: D002467:Cell Nucleus / Q000378:metabolism*; D002499:Centrifugation, Density Gradient; D002843:Chromatin / Q000378:metabolism; D004247:DNA / Q000032:analysis / Q000378:metabolism*; D003841:Deoxycytidine / Q000031:analogs & derivatives / Q000032:analysis; D003851:Deoxyribonucleases / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D006367:HeLa Cells; D006801:Humans; D006868:Hydrolysis; D008745:Methylation; D008836:Micrococcal Nuclease / Q000378:metabolism; D009707:Nucleosomes / Q000378:metabolism*; D013395:Sucrose; D013936:Thymidine / Q000032:analysis
chemical_list: D002843:Chromatin; D009707:Nucleosomes; D003841:Deoxycytidine; D013395:Sucrose; D004247:DNA; C016569:5-methyldeoxycytidine; D003851:Deoxyribonucleases; D008836:Micrococcal Nuclease; D013936:Thymidine