Abstract
Saccharomyces cerevisiae Mus81 is a structure-selective endonuclease which constitutes an alternative pathway
in parallel with the helicase-topoisomerase Sgs1-Top3-Rmi1 complex to resolve a number
of DNA intermediates during DNA replication, repair, and homologous recombination.
Previously, it was showed that the N-terminal region of Mus81 was required for its
in vivo function in a redundant manner with Sgs1; mus81Δ120N
mutant that lacks the first 120 amino acid residues at the N-terminus exhibited synthetic
lethality in combination with the loss of SGS1. In this study, the physiologically important role of the N-terminal region of Mus81
in processing toxic intermediates was further investigated. We examined the cellular
defect of sgs1Δmus81Δ100N
cells and observed that although viable, the cells became very sensitive to DNA damaging
agents. A single-copy suppressor screening to seek for a factor(s) that could rescue
the drug sensitivity of sgs1Δmus81Δ100N
cells was performed and revealed that Flp1, a site-specific recombinase 1 encoded
on the 2-micron plasmid was a suppressor. Moreover, Flp1 overexpression could partially
suppress the drug sensitivity of mus81Δ cells at 37 °C. Our findings suggest a possible function of Flp1 in coordination
with Mus81 and Sgs1 to jointly resolve the branched-DNA structures generated in cells
attempting to repair DNA damages.
Keywords
Flp1 - genetic screening - homologous recombination repair - Mus81 - Sgs1