Regulation of Mus81–Eme1 Holliday junction resolvase in response to DNA damage

Abstract

Structure-specific DNA endonucleases have critical roles during DNA replication, repair and recombination, yet they also harbor the potential for causing genome instability. Controlling these enzymes may be essential to ensure efficient processing of ad hoc substrates and to prevent random, unscheduled processing of other DNA structures, but it is unknown whether structure-specific endonucleases are regulated in response to DNA damage. Here, we uncover DNA damage-induced activation of Mus81-Eme1 Holliday junction resolvase in fission yeast. This novel regulation requires both Cdc2CDK1 and Rad3ATR-dependent phosphorylations of Eme1. Mus81-Eme1 activation prevents gross chromosomal rearrangements in cells lacking the BLM-related DNA helicase Rqh1. We propose that linking Mus81-Eme1 DNA damaged-induced activation to cell cycle progression ensures efficient resolution of Holliday junctions that escape dissolution by Rqh1-TopIII while preventing unnecessary DNA cleavages.

Temporal regulation of the Mus81-Mms4 endonuclease ensures cell survival under conditions of DNA damage

“…These results indicate that the absence of Sgs1 or Yen1 does not cause changes in the dynamics of activation of this endonuclease, even in the presence of DNA damage during chromosome replication. Moreover, these data also show that the hyperphosphorylation of Mms4 does not increase in budding yeast cells lacking Sgs1 with respect to SGS1 + cells (compare Figures 4A and 5A), unlike Eme1 Mms4 phosphorylation in S. pombe (46). Mms4 phosphorylation does not increase either in the absence of both Sgs1 and Yen1 (compare Figures 4A and 5B).…”

“…Therefore, the regulation of Mus81-Mms4 through Mms4 phosphorylation is independent of the presence of DNA damage during chromosome replication, even if the number of DNA lesions could accumulate due to pathological situations originated by the absence of proteins with which it has overlapping functions. A recent work has shown that, in S. pombe , Eme1 Mms4 phosphorylation is increased in G2 by damage induced by camptothecin or bleomycin, which is accompanied by enhanced activity of Mus81-Eme1 (46). However, our work indicates that MMS does not induce or modify the phosphorylation of budding yeast Mms4 and therefore the activity of Mus81-Mms4.…”

“…In addition, it has been proposed that in human cells, Mus81 is negatively controlled by Wee1 (45). Interestingly, a recent work has shown that, in S. pombe , the cell cycle–dependent phosphorylation of Eme1 Mms4 is Cdc2 CDK1 -dependent but Plo1 PLK1 -independent (46), unlike in budding yeast and human cells, thus showing differences among organisms in the way that Mus81-Eme1/Mms4 is regulated. Moreover, in fission yeast, Eme1 Mms4 hyperphosphorylation is stimulated when cells are treated with camptothecin or bleomycin.…”

“…Moreover, in fission yeast, Eme1 Mms4 hyperphosphorylation is stimulated when cells are treated with camptothecin or bleomycin. This induced-hyperphosphorylation is Rad3-dependent and increases the activity of S. pombe Mus81-Eme1 (46). …”

“…Yet, because this endonuclease can cleave DNA RFs, its activity must be carefully controlled somehow under these situations of DNA damage. Although above-mentioned works have shown that Mus81-Mms4 is activated when cells finish S-phase in the absence of damaged DNA (42,43), and in S. pombe its activity is enhanced by some DNA-damaging drugs in G2-cells (46), it is currently unclear how Mus81-Mms4 is regulated in response to DNA lesions occurring during replication. Here, we have analysed the role of budding yeast Mus81-Mms4 under conditions of DNA damage during S-phase and show that this endonuclease is necessary for successful chromosome replication when cells are exposed to MMS.…”