Fission yeast Ase1PRC1 is required for the G2-microtubule damage response

Schizosaccharomyces pombe delays entry into mitosis following G2 microtubule damage. This pathway is dependent on Rad26ATRIP, the regulatory subunit of the Rad26ATRIP/Rad3ATR DNA damage response (DDR) complex. However, this G2 microtubule damage response pathway acts independently of the G2 DNA damage checkpoint pathway. To identify other proteins in this G2 microtubule damage pathway, we previously screened a cDNA overexpression library for genes that rescued the sensitivity of rad26Δ cells to the microtubule poison thiabendazole. A partial cDNA fragment encoding only the C-terminal regulatory region of the microtubule bundling protein Ase1PRC1 was isolated. This fragment lacks the Ase1PRC1 dimerization and microtubule binding domains and retains the conserved C-terminal unstructured regulatory region. Here, we report that ase1Δ cells fail to delay entry into mitosis following G2 microtubule damage. Microscopy revealed that Rad26ATRIP foci localized alongside Ase1PRC1 filaments, although we suggest that this is related to microtubule-dependent double strand break mobility that facilitates homologous recombination events. Indeed, we report that the DNA repair protein Rad52 co-localizes with Rad26ATRIP at these foci, and that localization of Rad26ATRIP to these foci depends on a Rad26ATRIP N-terminal region containing a checkpoint recruitment domain. To our knowledge, this is the first report implicating Ase1PRC1 in regulation of the G2/M transition.