Enhanced c-fos expression in differentiated monomyelocytic cells is associated with differentiation and not with the position of the differentiated cells in the cell cycle.

Abstract

Enhanced expression of the proto-oncogene c-fos is reported to be involved in the differentiation of monomyelocytic cells into mature macrophages. Such differentiated cells usually accumulate in the G1 phase of the cell cycle. M1 murine myeloid leukemia cells, which can be synchronized in early and late G1 and can also differentiate into mature macrophages when stimulated with granulocyte colony-stimulating factor (G-CSF), were used to investigate whether the enhanced expression of c-fos in differentiated monomyelocytic cells is associated with the position of the cells in the cell cycle or with their state of differentiation. Our data show that the enhanced expression of the c-fos gene occurs only in fully differentiated cells and not in proliferating or G1-arrested cells. These data imply that the enhanced expression of c-fos in M1 cells is restricted to functionally differentiated cells and not related to the position of the differentiated cells in the cell cycle.