Srs2 promotes Mus81-Mms4-mediated resolution of recombination intermediates.
Bottom Line: Second, Srs2 removes Rad51 from DNA to allow access of Mus81-Mms4 to cleave DNA.Concomitantly, Mus81-Mms4 inhibits the helicase activity of Srs2.Taken together, our data point to a coordinated role of Mus81-Mms4 and Srs2 in processing of recombination as well as replication intermediates.
Affiliation: Department of Biology, Masaryk University, Kamenice 5/A7, Brno 625 00, Czech Republic National Centre for Biomolecular Research, Masaryk University, Kamenice 5/A4, Brno 625 00, Czech Republic.Show MeSH
Related in: MedlinePlus
Mentions: Our biochemical data prompted us to test whether Srs2 and Mus81 co-localize in vivo with or without DNA damage. Only ∼9% of the budded cells contained spontaneous Mus81 foci and this formation was induced up to 20% by treatment with CPT or Zeocin. In contrast, treatment of the cells with HU had no significant effect on Mus81 focus formation (Figure 7). Accordingly, we observed significant co-localization of Srs2 and Mus81 foci after treatment with CPT, indicating a role for these proteins in the repair of CPT-induced damage (Figure 7). The co-localization of Mus81 and Srs2 after Zeocin treatment is also significant and was further enhanced by prolonged treatment (Figure 7B), suggesting that Srs2 and Mus81 function together in the repair of chromosome damage. Analysis of cell cycle stage shows culmination of Srs2 foci in S/G2, co-localization foci with Mus81 in G2 and Mus81 foci alone in G2/M phase (Figure 7C), suggesting that Srs2 might be responsible for targeting Mus81 to sites of DNA repair. However, Mus81 was fully proficient in focus formation in the absence of Srs2 (Supplementary Figure S5). Further, there was a statistically significant increase in spontaneous Mus81 foci in the srs2 strain that was further increased upon DNA damage. Such a result is consistent with the idea that this strain accumulates toxic recombination intermediates that are targets for Srs2-independent recruitment of Mus81. Taken together, these results are consistent with DNA damage-induced co-localization of Mus81 and Srs2. The fact that Srs2 focus formation precedes Mus81 suggests that Srs2 could play a role in its regulation at the site of repair.
Affiliation: Department of Biology, Masaryk University, Kamenice 5/A7, Brno 625 00, Czech Republic National Centre for Biomolecular Research, Masaryk University, Kamenice 5/A4, Brno 625 00, Czech Republic.