| Modification Notes |
In budding yeast, loss of topoisomerase III, encoded by the TOP3 gene, leads to a genomic instability phenotype that includes slow growth, hyper-sensitivity to genotoxic agents, mitotic hyper-recombination, increased chromosome missegregation, and meiotic failure. The Saccharomyces cerevisiae TOP3 gene is highly conserved in evolution. The RecQ DNA helicase, yeast Sgs1, forms a complex with topoisomerase III (Top3) and functions during DNA replication to restart forks that have paused due to DNA damage or topological stress. The N-terminal region of Sgs1, which interacts with Top3, is required for complementation of MMS sensitivity and suppression of hyper-recombination in Sgs1 disruptants. Slow growth and other defects of Top3 mutants are suppressed by mutation of Sgs1. Sgs1 is a homologue of the human Bloom’s syndrome and Werner’s syndrome genes. |