c-myc mRNA levels in the cell cycle change in mouse erythroleukemia cells following inducer treatment

Several lines of evidence suggest that the c-myc protooncogene is involved in some aspect of cell division in mammalian cells. We have been investigating changes in the expression of c-myc mRNA in mouse erythroleukemia cells during chemically induced terminal erythroid differentiation. In vitro induction of erythroleukemia cell differentiation results in a switch from cells with unlimited proliferative capacity to cells that undergo a small number of terminal cell divisions. The level of c-myc mRNA changes rapidly following treatment with inducing agents. After a very rapid decline the mRNA is restored to pretreatment levels and then declines again. We have now measured the level of c-myc mRNA with respect to position in the cell cycle. Prior to inducer treatment the level of c-myc mRNA is relatively constant throughout the cell cycle. However, when the mRNA is restored following treatment with hypoxanthine or hexamethylenebisacetamide, it is found primarily in cells in the G₁ phase. Thus, treatment with inducers of differentiation leads to a change in the cell cycle regulation of c-myc mRNA. This change may involved in the altered proliferative capacity of the cells that occurs during terminal differentiation.