Dot1-Dependent Histone H3K79 Methylation Promotes the Formation of Meiotic Double-Strand Breaks in the Absence of Histone H3K4 Methylation in Budding Yeast

Abstract

Epigenetic marks such as histone modifications play roles in various chromosome dynamics in mitosis and meiosis. Methylation of histones H3 at positions K4 and K79 is involved in the initiation of recombination and the recombination checkpoint, respectively, during meiosis in the budding yeast. Set1 promotes H3K4 methylation while Dot1 promotes H3K79 methylation. In this study, we carried out detailed analyses of meiosis in mutants of the SET1 and DOT1 genes as well as methylation-defective mutants of histone H3. We confirmed the role of Set1-dependent H3K4 methylation in the formation of double-strand breaks (DSBs) in meiosis for the initiation of meiotic recombination, and we showed the involvement of Dot1 (H3K79 methylation) in DSB formation in the absence of Set1-dependent H3K4 methylation. In addition, we showed that the histone H3K4 methylation-defective mutants are defective in SC elongation, although they seem to have moderate reduction of DSBs. This suggests that high levels of DSBs mediated by histone H3K4 methylation promote SC elongation.

The Double-Strand Break Landscape of Meiotic Chromosomes Is Shaped by the Paf1 Transcription Elongation Complex in Saccharomyces cerevisiae

“…Moreover, Rtf1 may have a negative (repressive) role on DSB formation in the absence of two histone methylation marks, H3K4me and H3K79me. Previous results showed that the combination of the set1 and dot1 mutations can suppress dmc1 arrest in prophase I (Bani Ismail et al 2014). On the other hand, the rtf1 mutation did not suppress the arrest ( Figure S2B).…”

“…Compared to the time of MI onset in wild-type cells, rtf1 mutant cells entered MI with an 2.5-hr delay. The delay in the rtf1 mutant was 2 hr shorter than the delay in the set1 mutant ( Figure 1C) (Sollier et al 2004;Bani Ismail et al 2014). Importantly, the rtf1 set1 double mutant showed similar kinetics of entry into MI as the rtf1 single mutant, suggesting that Rtf1 works upstream of Set1.…”

“…Given the established role of Paf1C-dependent histone H3K4 and H3K79 methylation marks in the formation of meiotic DSBs (Sollier et al 2004;Borde et al 2009;Bani Ismail et al 2014), we evaluated the effect of the rtf1 mutation on the formation of meiotic DSBs. First, we studied DSB repair at the recombination hotspot HIS4-LEU2 (Figure 2A).…”

“…Previous studies in budding yeast showed that methylation of two histone H3 lysines, H3K4 and H3K79, has a important role during meiotic DSB formation (Sollier et al 2004;Borde et al 2009;Bani Ismail et al 2014). In particular, histone H3K4 methylation is a critical determinant of efficient DSB formation as well as selection of DSB sites (Borde et al 2009;Acquaviva et al 2013;Sommermeyer et al 2013).…”

“…deletion mutants were described previously (Bani Ismail et al 2014). The primers used for strain construction are listed in Table S2.…”