MCL1, also known as BCL2L3, belongs to the Bcl-2 family. MCL1 is involved in the regulation of apoptosis versus cell survival, and in the maintenance of viability but not of proliferation. Alternative splicing occurs at this locus and two transcript variants encoding distinct isoforms have been identified. The longer gene product (isoform 1) enhances cell survival by inhibiting apoptosis while the alternatively spliced shorter gene product (isoform 2) promotes apoptosis and is death-inducing.