The function of MCL1 (MCL1 apoptosis regulator, BCL2 family member, Ensembl gene identifier ENSG00000143384) is as follows. Involved in the regulation of apoptosis versus cell survival, and in the maintenance of viability but not of proliferation. Mediates its effects by interactions with a number of other regulators of apoptosis. Isoform 1 inhibits apoptosis. Isoform 2 promotes apoptosis. .