ELEVATION OF INTERNAL 6-METHYLADENINE MESSENGER-RNA METHYLTRANSFERASEACTIVITY AFTER CELLULAR-TRANSFORMATION

A comparison of internal 6-methyladenine mRNA methyltransferase activi ty in a variety of cell types demonstrated an 8-15-fold increase as a result of cellular transformation. Utilizing adenovirus transformed ra t embryo cells, it was found that the increase in methyltransferase ac tivity was concomitant with or occurred rapidly after transformation. An 8-fold increase in activity was observed in the cells isolated from the transformed foci and remained elevated through subsequent passage s. The relationship between methyltransferase activity and tumor forma tion was also investigated. High level expression of the avian ski onc ogene in mouse L cells causes a reversion of the transformed phenotype to a non-transformed state, and resulted in a 47% reduction in the sp ecific activity of the methyltransferase as compared with mock transfe cted cells.