Involvement of cdc13+ in mitotic control in Schizosaccharomyces pombe: possible interaction of the gene product with microtubules.

Abstract

Previous genetic studies have shown that the fission yeast cdc13+ gene product interacts closely with the cdc2+ protein kinase during mitosis. Here, we have cloned the cdc13+ gene from a S. pombe gene bank by complementation of the temperature‐sensitive defect of a cdc13‐117 mutant strain. The complementing activity was localized to a 1.9‐kb XbaI‐NsiI DNA fragment, and nucleotide sequencing revealed a 1446‐bp open reading frame. The predicted amino acid sequence contained 482 residues and was not homologous to any protein in a protein database. The cdc13+ gene function was confirmed to be essential for cell division since cells carrying a cdc13 null allele arrested with a cdc phenotype. However, unlike any existing temperature‐sensitive cdc13 mutants, cdc13 null mutants arrested in G2 without septa or condensed chromosomes indicating that cdc13+ gene function is required at or prior to the initiation of mitotis. cdc13‐117 mutant strains were found to be hypersensitive to the tubulin inhibitor thiabendazole. This observation suggests that the cdc13+ gene product, which is required for mitotic initiation, may interact with microtubules.