Incenp and an Aurora-like kinase form a complex essential for chromosome segregation and efficient completion of cytokinesis

Background: In animal cells, cytokinesis begins shortly after the sister ch romatids move to the spindle poles. The inner centromere protein (Incenp) h as been implicated in both chromosome segregation and cytokinesis, but it i s not known exactly how it mediates these two distinct processes. Results: We identified two Caenorhabditis elegans proteins, ICP-1 and ICP-2 , with significant homology in their carboxyl termini to the corresponding region of vertebrate Incenp. Embryos depleted of ICP-1 by RNA-mediated inte rference had defects in both chromosome segregation and cytokinesis. Deplet ion of the Aurora-like kinase AIR-2 resulted in a similar phenotype. The ca rboxy-terminal region of Incenp is also homologous to that in Sli15p, a bud ding yeast protein that functions with the yeast Aurora kinase IpI1p. ICP-I bound C. elegans AIR-2 in vitro, and the corresponding mammalian orthologs Incenp and AIRK2 could be co-immunoprecipitated from cell extracts. A sign ificant fraction of embryos depleted of ICP-1 and AIR-2 completed one cell division over the course of several cell cycles. ICP-1 promoted the stable localization of ZEN-4 (also known as CeMKLP1), a kinesin-like protein requi red for central spindle assembly. Conclusions: ICP-I and AIR-2 are part of a complex that is essential for ch romosome segregation and for efficient completion of cytokinesis. We propos e that this complex acts by promoting dissolution of sister chromatid cohes ion and the assembly of the central spindle. (C) 2000 Elsevier Science Ltd. All rights reserved.