Apoptosis inhibitor 4/Birc5 Protein, Mouse (P.pastoris, His)

Apoptosis inhibitor 4/Birc5, a versatile protein, assumes dual roles in promoting cell proliferation and thwarting apoptosis. As a crucial component of the chromosome passage protein complex (CPC), Birc5 plays an essential role in orchestrating chromosome alignment and segregation throughout mitosis and cytokinesis. It directs CPC movement, ensuring its localization shifts from the inner centromere in prometaphase to the midbody during cytokinesis, contributing to the organization of the central spindle by associating with polymerized microtubules. Birc5 is instrumental in recruiting CPC to centromeres during early mitosis, binding to histone H3 phosphorylated at 'Thr-3' (H3pT3). Functioning in concert with RAN, Birc5 aids in mitotic spindle formation, acting as a scaffold for the delivery of the RAN effector molecule TPX2 to microtubules. Additionally, it counteracts default induction of apoptosis in G2/M phase and, when acetylated, represses STAT3 transactivation of target gene promoters. Birc5 serves as an inhibitor of CASP3 and CASP7, crucial for the maintenance of mitochondrial integrity and function. Existing as a monomer in the CPC-bound state, Birc5 protects cells against apoptosis more efficiently than in its homodimeric form. It engages in a complex network of interactions with various proteins, such as histone H3, RAN, tubulin, XIAP/BIRC4, and DIABLO/SMAC, highlighting its multifaceted regulatory functions in cellular processes.