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

Institute of Molecular Agrobiology, The National University of Singapore, Singapore.
FEBS Letters (Impact Factor: 3.34). 11/1999; 460(1):187-90. DOI: 10.1016/S0014-5793(99)01329-0
Source: PubMed

ABSTRACT Proteins containing the baculovirus inhibitor of apoptosis repeats (BIR domains) have been identified in a wide range of species. BIR domain containing 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-like proteins have not been found in yeasts, suggesting that the BIR domain containing proteins might play a fundamental role in cell regulation, in addition to their well-characterized role in inhibition of apoptosis. In this study, we have characterized Pbh1p, an S. pombe BIR domain containing protein. Construction and analysis of a null mutant in pbh1+ revealed that pbh1+ is essential for cell viability. Moreover, cells devoid of Pbh1p are defective in chromosome condensation and chromosome segregation. Thus, proper chromosome segregation requires the function of Pbh1p. Over-production of Pbh1p led to abnormalities in mitosis and cytokinesis, suggesting that the levels of Pbh1p are important for regulation of mitosis and cytokinesis.

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    ABSTRACT: Survivin is a member of the inhibitor of apoptosis (IAP) gene family, containing a single baculovirus IAP repeat (BIR) and no RING finger, that is expressed in many human cancers. Although it has been proposed to be involved in mitotic and cytokinetic processes, its functional subcellular distribution in the cytoplasm and nucleus, and its binding to centrosomes, spindle fibers, and centromeres in relation to these processes, is not fully resolved. We have analyzed the localization of Survivin in normal (Detroit 551, IMR-90) and tumor-derived (HeLa, Saos-2) cell lines, and found that it does colocalize with centrosomes in the cytoplasm during interphase, then moves to centromeres during mitosis, and finally localizes to the midbody spindle fibers during telophase. However, Taxol, a popular microtubule stabilizing agent that is frequently used in the study of these processes, severely disrupted the localization of Survivin. Taxol treatment of cells promoted extensive relocalization of Survivin with α-tubulin on microtubules during either interphase or mitosis. Survivin antisense oligonucleotide markedly sensitized HeLa cells to cell death induced by agents acting at the level of cell surface receptor (Fas pathway) or at the level of mitochondria (etoposide). HeLa cell death induced by Survivin antisense oligonucleotide could be partially complemented by Deterin, the Drosophila homolog of Survivin (Jones et al. [2000] J. Biol. Chem. 275:22157–22166). Reciprocally, a chimera of the Deterin BIR domain and Survivin C-terminus could rescue Drosophila Kc cells from death induced by transfection of a human caspase-7-expressing plasmid. These results indicate common components of Survivin and Deterin antiapoptotic action in the vertebrate and invertebrate phyla. J. Cell. Biochem. 83: 342–354, 2001. © 2001 Wiley-Liss, Inc.
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    ABSTRACT: Survivin is a key cellular protein thought to function in apoptotic regulation, mitotic progression, or possibly both. In this study, we describe the isolation of two conditional knockouts of the survivin gene in chicken DT40 cells. DT40 cells lacking Survivin die in interphase after failing to complete cytokinesis. However, these cells show normal sensitivity to the chemotherapeutic agent etoposide. Expression of Survivin mutants against a null background to reassess the role of several key residues reveals that DT40 cells can grow normally if their sole Survivin is missing a widely studied cyclin-dependent kinase phosphorylation site or sites reportedly essential for binding to Smac or aurora B. Mutations in the nuclear export sequence or dimerization interface render cells temperature sensitive for growth. As an important caveat for other studies in which protein function is studied by transient transfection, three of the Survivin mutants fail to localize in the presence of the wild-type protein but do localize and indeed support life in its absence.
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    ABSTRACT: Inhibitor-of-apoptosis proteins (IAPs), including neuronal apoptosis inhibitory protein (NAIP), inhibit cell death. Other IAPs inhibit key caspase proteases which effect cell death, but the mechanism by which NAIP acts is unknown. Here we report that NAIP, through its third baculovirus inhibitory repeat domain (BIR3), binds the neuron-restricted calcium-binding protein, hippocalcin, in an interaction promoted by calcium. In neuronal cell lines NSC-34 and Neuro-2a, over-expression of the BIR domains of NAIP (NAIP-BIR1-3) counteracted the calcium-induced cell death induced by ionomycin and thapsigargin. This protective capacity was significantly enhanced when NAIP-BIR1-3 was co-expressed with hippocalcin. Over-expression of the BIR3 domain or hippocalcin alone did not substantially enhance cell survival, but co-expression greatly increased their protective effects. These data suggest synergy between NAIP and hippocalcin in facilitating neuronal survival against calcium-induced death stimuli mediated through the BIR3 domain. Analysis of caspase activity after thapsigargin treatment revealed that caspase-3 is activated in NSC-34, but not Neuro-2a, cells. Thus NAIP, in conjunction with hippocalcin, can protect neurons against calcium-induced cell death in caspase-3-activated and non-activated pathways.
    The EMBO Journal 08/2000; 19(14):3597-607. · 10.75 Impact Factor


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