Novel pof1 mutation suppresses the sensitivity to DNA replication inhibitor in fission yeast RecQ helicase mutant

Homologous recombination is vital for DNA double-strand break repair. Dysfunction in homologous recombination can lead to cell death, mutations, and cancer. In fission yeast (Schizosaccharomyces pombe), RecQ helicase Rqh1 resolves recombination intermediates. We found that rqh1-hd strain impaired growth in media containing hydroxyurea and thiabendazole. Using this condition, we identified a novel pof1 mutation (pof1-A81T) that suppress the poor growth of the rqh1-hd strain on the plate containing hydroxyurea and thiabendazole. Compared to rqh1-hd, rqh1-hd pof1-A81T cells displayed reduced Replication Protein A foci on chromosome bridges after hydroxyurea treatment. This suggests that pof1-A81T mutation suppresses the accumulation of recombination intermediates in hydroxyurea-treated rqh1-hd cells. Additionally, pof1-A81T mutation rescued the segregation defect of nucleolar protein Gar2 observed in hydroxyurea-treated rqh1-hd cells, potentially by mitigating recombination intermediate accumulation in rDNA. These results suggest that the pof1-A81T mutation suppresses the accumulation of recombination intermediates, particularly in rDNA, and alleviates the rqh1 deficiency phenotype in S. pombe.