Intracellular distribution of DNA methyltransferase during the cell cycle.

The intracellular distribution of DNA methyltransferase has been analyzed in synchronously proliferating human cells. The localization of DNA methyltransferase was determined immunocytochemically using monoclonal antibodies directed against this enzyme. DNA methyltransferase was found to accumulate predominantly in nuclei with weak cytoplasmic staining. The DNA methyltransferase antigen was absent in early G1 phase, appeared in late G1 prior to the onset of DNA synthesis and persisted throughout S and G2 phases of the cell cycle. Mitotic cells showed a particularly strong staining intensity. These results show that DNA methyltransferase levels fluctuate during the cell cycle. This has possible implications on the stability of the DNA methylation pattern.