The survivin-like C-elegans BIR-1 protein acts with the aurora-like kinaseAIR-2 to affect chromosomes and the spindle midzone

Baculoviral IAP repeat proteins (BIRPs) may affect cell death, cell divisio n, and tumorigenesis. The C. elegans BIRP BIR-l was localized to chromosome s and to the spindle midzone. Embryos and fertilized oocytes lacking BIR-1 had defects in chromosome behavior, spindle midzone formation, and cytokine sis. We observed indistinguishable defects in fertilized oocytes and embryo s lacking the Aurora-like kinase AIR-2. AIR-2 was not present on chromosome s in the absence of BIR-I. Histone H3 phosphorylation and HCP-1 staining, w hich marks kinetochores, were reduced in the absence of either BIR-1 or AIR -2. We propose that BIR-l localizes AIR-2 to chromosomes and perhaps to the spindle midzone, where AIR-2 phosphorylates proteins that affect chromosom e behavior and spindle midzone organization. The human BIRP survivin, which is upregulated in tumors, could partially substitute for BIR-1 in C. elega ns. Deregulation of bir-l promotes changes in ploidy, suggesting that simil ar deregulation of mammalian BIRPs may contribute to tumorigenesis.