Mcl1 is an anti-apoptotic member of Bcl2 family originally isolated from the ML1 human myeloid leukemia cell line during phorbol ester-induced differentiation along the monocyte/macrophage pathway. Mcl1 localizes to the mitochondria, interacts with and antagonizes pro-apoptotic Bcl2 family members, and inhibits apoptosis by a number of cytotoxic stimuli. It is involved in programing of differentiation and concomitant maintenance of viability but not of proliferation. Isoform 1 inhibits apopt