Abstract
Mouse L-cell DNA radioactively labeled in the 5-methylcytosine (5-MeC) residue was fractionated into satellite and main band DNA. Satellite DNA was found to contain about four times the molar concentration of 5-MeC than the main band DNA. Based on the known 5-MeC content of total L-cell DNA it was calculated that satellite DNA contains 3.5 – 4.6% 5-MeC. Both DNA fractions were depurinated and the pyrimidine oligonucleotides released separated by ionophoresis-homochromatography. In satellite DNA 5-MeC is distributed non-randomly. About 40% of the total 5-MeC is present in the sequence Pu - 5-MeC - Pu. The remainder occurs in the oligonucleotides CT, CT 3, C 2T 4, C 2T 5 and C 3T 5 only. The distribution of 5-MeC in main band DNA differs from that in satellite DNA indicating that two different fractions of the same nuclear DNA are methylated in different sequences.
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