Interleukin 3-dependent Proliferation of the Human MO-7e Cell Line Is Supported by Discrete Activation of Late d Genes

The hemopoietic growth factor interleukin 3 (IL-3) supports the survival and proliferation of multipotent and committed progenitor cells in vitro. To elucidate the molecular mechanisms triggered by IL-3 we studied the expression of cell cycle-related genes in a recently established human IL-3-de pendent clone (M-07e). No changes in the level of expression of early (c-myc), mid (ornithine decarboxylase), or mid-late Gi (p53, c-myb) cell cycle genes were detected after restoration of IL-3 in deprived cells. The fact that only late Gi-S-phase genes [proliferating cell nuclear antigen (PCNA) thymidine kinase (TK), histone H3] are modulated by IL-3 suggests that this factor may control human cell proliferation by acting at the d-S boundary.