Proliferation-associated expression of DNA methyltransferase in human embryonic lung cells.

The cell cycle-dependent and proliferation-associated expression of the enzyme DNA methyltransferase has been evaluated immunocytochemically in synchronized L-132 human embryonic lung cells, using the anti-DNA methyltransferase monoclonal antibody M1F6D7/5C10. DNA methyltransferase-reactivity was firstly seen in mid-G1 cells. An intense and granular reaction in the cell nuclei with a sparing of the nucleoli was observed in addition to a homogenous and faint cytoplasmic staining. The staining intensity in the cell nuclei increased progressively up to mitosis. In early mitotic cells an intense perichromosomal staining was observed in addition to a homogenous staining of cyto- and karyoplasm after the resolving of the core membrane. In late mitosis the staining intensity decreased rapidly. Early G1 cells and density inhibited, resting G0 cells showed no DNA methyltransferase reactivity at all. Our results indicate that anti-DNA methyltransferase monoclonal antibodies could become valuable tools to detect proliferating cells in cell cultures and tissues.