DNA methylation in various growth phases of cultured L5178Y murine lymphoblasts.

The extent of methylation of DNA during the transition of cells from exponential phase of growth to the saturation density has been studied in cultured L5178Y mouse lymphoma cells by the comparison of the degree of 5-methylcytosine formation and the stability of this preformed base in various periods of their growth. It has been found that while the degree of 5-methylcytosine formation gradually fell down, the level of this base preformed during the exponential growth was stable during the subsequent periods until the saturation density was reached. At that state some small and variable loss of the base was found.