title: 5-Methylcytosine content of rat hepatoma DNA substituted with bromodeoxyuridine.
abstract: The aim of these experiments was to test whether incorporation of bromodeoxyuridine into DNA affects DNA methylation. Rat hepatoma (HTC) cells in culture were labeled for two generations with [14C]bromodeoxyuridine and [3H]thymidine to yield DNA which was 2.1, 20.6, 52.6, and 95.0% bromodeoxyuridine-substituted in the newly made strands. The DNA then was fractionated into highly repetitive, moderately repetitive, and single copy sequences. As determined by a comparison of 14C and 3H counts per min, the percentage of substitution with bromodeoxyuridine was found to be the same in each repetition class. The 5-methylcytosine content of each fraction was determined using high pressure liquid chromatography. It was found that bromodeoxyuridine, even at a level of substitution into newly mad DNA of 95%, has no effect on the 5-methylcytosine content of DNA. At all levels of bromodeoxyuridine substitution, highly repetitive DNA has slightly more 5-methylcytosine (3.0% of total cytosine) than does single copy DNA or moderately repetitive DNA (2.3%). The 5-methylcytosine content of whole HTC DNA is the same as that of rat liver DNA (2.4%).
mesh_terms: D000818:Animals; D001973:Bromodeoxyuridine / Q000378:metabolism* / Q000494:pharmacology; D006528:Carcinoma, Hepatocellular / Q000378:metabolism*; D002460:Cell Line; D003596:Cytosine / Q000031:analogs & derivatives* / Q000032:analysis; D004273:DNA, Neoplasm / Q000096:biosynthesis / Q000302:isolation & purification; D008113:Liver Neoplasms / Q000378:metabolism*; D009691:Nucleic Acid Denaturation; D009695:Nucleic Acid Renaturation; D051381:Rats
chemical_list: D004273:DNA, Neoplasm; D003596:Cytosine; D001973:Bromodeoxyuridine