The protein encoded by this gene belongs to the Bcl-2 family. 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. The protein MCL1 has a very short biological half-life of only 20–30 minutes.
The loss of MCL1 has a more dramatic impact than the loss of any other anti-apoptotic member of the Bcl-2 family. Loss of the Mcl-1 gene results in embryo death when the embryo is only around 3.5 days old, before it has even implanted. Conditional deletion of Mcl-1 depletes a wide variety of cells, including hematopoietic stem cells, B cell–committed progenitors, T cell–committed progenitors, antibody-secreting plasma cells, cardiac muscle cells, and neurons.
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