The Aurora-related kinase AIR-2 recruits ZEN-4/CeMKLP1 to the mitotic spindle at metaphase and is required for cytokinesis

Background: The Aurora/IpI1p-related kinase AIR-2 is required for mitotic c hromosome segregation and cytokinesis in early Caenorhabditis elegans embry os. Previous studies have relied on non-conditional mutations or RNA-mediat ed interference (RNAi) to inactivate AIR-2, It has therefore not been possi ble to determine whether AIR-2 functions directly in cytokinesis or if the cleavage defect results indirectly from the failure to segregate DNA. One i ntriguing hypothesis is that AIR-2 acts to localize the mitotic kinesin-lik e protein ZEN-4 (also known as CeMKLP1), which later functions In cytokines is. Results: Using conditional alleles, we established that AIR-2 is required a t metaphase or early anaphase for normal segregation of chromosomes, locali zation of ZEN-4, and cytokinesis. ZEN-4 is first required late in cytokines is, and also functions to maintain cell separation through much of the subs equent Interphase. DNA segregation defects alone were not sufficient to dis rupt cytokinesis in other mutants, suggesting that AIR-2 acts specifically during cytokinesis through ZEN-4. AIR-2 and ZEN-4 shared similar genetic in teractions with the formin homology (FH) protein CYK-1, suggesting that AIR -2 and ZEN-4 function in a single pathway, in parallel to a contractile rin g pathway that includes CYK-1. Using in vitro co-immunoprecipitation experi ments, we found that AIR-2 and ZEN-4 interact directly. Conclusions: AIR-2 has two functions during mitosis: one in chromosome segr egation, and a second, independent function in cytokinesis through ZEN-4. A IR-2 and ZEN-4 may act in parallel to a second pathway that includes CYK-1. (C) 2000 Elsevier Science Ltd. All rights reserved.