MLF1 (Myeloid leukemia factor 1) belongs to MLF family, and is a widely expressed negative regulator of cell cycle progression functioning upstream of the tumor suppressor p53. This protein interferes with erythropoietin-induced erythroid terminal differentiation by preventing cells from exiting the cell cycle through suppression of CDKN1B/p27Kip1 levels. MLF1 normally functions in multi-potent progenitor cells, and its dysregulation may be somewhat responsible for leukemogenesis.