Cyclic AMP and c-myc gene expression in PY815 mouse mastocytoma cells.

The possibility was examined that inhibition of growth of PY815 mouse mastocytoma cells by N6,O2'-dibutyryladenosine 3',5'-cyclic monophosphate (DB cyclic AMP) results from inhibition of c-myc gene expression. Temporary increases in c-myc RNA which occurred soon after DB cyclic AMP treatment and upon removal of the drug were not consistent with direct inhibition of c-myc gene expression by DB cyclic AMP. The increases in c-myc RNA coincided with the passage through, or accumulation of cells in late G1-early S phase. It is proposed that cyclic AMP may stimulate c-myc gene expression which normally occurs only in late G1-early S phase in PY815 cells and that cyclic AMP prevents c-myc expression in cells at other phases of the cell cycle by inhibiting their progression past a cyclic AMP-sensitive restriction point in early G1 phase.