Fission yeast Ase1(PRC1) is required for the G(2)-microtubule damage response

Schizosaccharomyces pombe delays entry into mitosis following G(2) microtubule damage. This pathway is dependent on Rad26(ATRIP), the regulatory subunit of the Rad26(ATRIP)/Rad3(ATR) DNA damage response (DDR) complex. However, this G(2) microtubule damage response pathway acts independently of the G(2) DNA damage checkpoint pathway. To identify other proteins in this G(2) 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 Ase1(PRC1 )was isolated. This fragment lacks the Ase1(PRC1) 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 G(2) microtubule damage. Microscopy revealed that Rad26(ATRIP) foci localized alongside Ase1(PRC1) 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 Rad26(ATRIP )at these foci, and that localization of Rad26(ATRIP) to these foci depends on a Rad26(ATRIP) N-terminal region containing a checkpoint recruitment domain. To our knowledge, this is the first report implicating Ase1(PRC1) in regulation of the G(2)/M transition.