Journal
JOURNAL OF BIOLOGICAL CHEMISTRY
Volume 275, Issue 10, Pages 6707-6711Publisher
AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
DOI: 10.1074/jbc.275.10.6707
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Funding
- NHLBI NIH HHS [HL54131] Funding Source: Medline
- NIGMS NIH HHS [GM59167, R01 GM055316, R01 GM059167, GM55316] Funding Source: Medline
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The inhibitor of apoptosis (IAP) gene family comprises molecules that block the activity of pro-apoptotic caspase proteases, Paradoxically, yeasts contain IAP proteins but no caspases and no apoptotic program. To determine the function of these proteins in vivo, we disrupted the BIR1 gene, encoding the only known IAP in yeast Saccharomyces cerevisiae, Sporulation of heterozygous diploids yielded no viable mutant haploids, indicating that BIR1 is an essential gene. By flow cytometry, some heterozygous mutants were polyploid accumulating >4 N DNA content. These cells exhibited a 20-40% reduction in growth rate, which was rescued by plasmid-borne over-expression of BIR1 but not by its human counterpart, survivin, Deletion analysis revealed that the N-terminal domain of Bir1, containing the conserved baculovirus IAP repeat, was able to partially complement the cell growth defect caused by BIR1 deletion. Moreover, the full-length and truncated forms of Bir1 accelerated cell division in wild-type cells. Finally, BIR1 heterozygous mutants exhibited grossly altered cell morphology with mis-shapen or abnormally long buds connected to an unusually large mother cell. These findings identify a novel function of IAP proteins in the pleiotropic control of cell division, in addition to their role in the suppression of apoptosis.
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