S-pombe Pbh1p: an inhibitor of apoptosis domain containing protein is essential for chromosome segregation

Proteins containing the baculovirus inhibitor of apoptosis repeats (BIR dom ains) have been identified in a wide range of species. BIR domain containin g proteins are thought to inhibit caspases and thereby cause inhibition of apoptosis, A BIR domain containing protein has been recently identified by the Schizosaccharomyces pombe genome sequencing project. However, caspase-l ike proteins have not been found in yeasts, suggesting that the BIR domain containing proteins might play a fundamental role in cell regulation, in ad dition to their well-characterized role in inhibition of apoptosis, In this Study, we have characterized Pbh1p, an S, pombe BIR domain containing prot ein. Construction and analysis of a null mutant in pbh1(+) revealed that pb H1(+) is essential for cell viability. Moreover, cells devoid of Pbh1p are defective in chromosome condensation and chromosome segregation. Thus, prop er chromosome segregation requires the function of Pbh1p, Over-production o f Pbh1p led to abnormalities in mitosis and cytokinesis, suggesting that th e levels of Pbh1p are important for regulation of mitosis and cytokinesis, (C) 1999 Federation of European Biochemical Societies.