B-type cyclins CLB5 and CLB6 control the initiation of recombination and synaptonemal complex formation in yeast meiosis

106

An E2 ubiquitin-conjugating enzyme, Rad6, working with an E3 ubiquitin ligase Bre1, catalyzes monoubiquitylation of histone H2B on a C-terminal lysine residue. The rad6 mutant of Saccharomyces cerevisiae shows a meiotic prophase arrest. Here, we analyzed meiotic defects of a rad6 null mutant of budding yeast. The rad6 mutant exhibits pleiotropic phenotypes during meiosis. RAD6 is required for efficient formation of double-strand breaks (DSBs) at meiotic recombination hotspots, which is catalyzed by Spo11. The mutation decreases overall frequencies of DSBs in a cell. The effect of the rad6 mutation is local along chromosomes; levels of DSBs at stronger hotspots are particularly reduced in the mutant. The absence of RAD6 has little effect on the formation of ectopic DSBs targeted by Spo11 fusion protein with a Gal4 DNA-binding domain. Furthermore, the disruption of the BRE1 as well as substitution of the ubiquitylation site of histone H2B also reduces some DSB formation similar to the rad6. These results suggest that Rad6-Bre1, through ubiquitylation of histone H2B, is necessary for efficient recruitment and͞or stabilization of a DSB-forming machinery containing Spo11. Histone tail modifications might play a role in DSB formation during meiosis.

Section: Discussionmentioning

confidence: 80%

Rad6-Bre1-mediated histone H2B ubiquitylation modulates the formation of double-strand breaks during meiosis

Yamashita

Shinohara

2004

106

“…Strong coupling between premiotic DNA replication and meiotic recombination has been reported in budding yeast (6)(7)(8)(9). Although premeiotic DNA replication is slightly delayed in hsk1-89 cells, evidence indicates that recombination and meiotic defects may not be consequences of incomplete DNA replication.…”

Section: Discussionmentioning

confidence: 89%

“…It is not known whether initiation is regulated by a common mechanism or the same set of replication origins is used during premeiotic S phase. In budding yeast, strong coupling of DNA replication and meiotic recombination has been shown (6)(7)(8)(9).…”

mentioning

confidence: 99%

Hsk1 kinase is required for induction of meiotic dsDNA breaks without involving checkpoint kinases in fission yeast

Ogino¹,

Hirota

Matsumoto³

et al. 2006

Self Cite

Cdc7 kinase, conserved through evolution, is known to be essential for mitotic DNA replication. The role of Cdc7 in meiotic recombination was suggested in Saccharomyces cerevisiae, but its precise role has not been addressed. Here, we report that Hsk1, the Cdc7-related kinase in Schizosaccharomyces pombe, plays a crucial role during meiosis. In a hsk1 temperature-sensitive strain (hsk1-89), meiosis is arrested with one nucleus state before meiosis I in most of the cells and meiotic recombination frequency is reduced by one order of magnitude, whereas premeiotic DNA replication is delayed but is apparently completed. Strikingly, formation of meiotic dsDNA breaks (DSBs) are largely impaired in the mutant, and Hsk1 kinase activity is essential for these processes. Deletion of all three checkpoint kinases, namely Cds1, Chk1, and Mek1, does not restore DSB formation, meiosis, or Cdc2 activation, which is suppressed in hsk1-89, suggesting that these aberrations are not caused by known checkpoint pathways but that Hsk1 may regulate DSB formation and meiosis. Whereas transcriptional induction of some rec genes and horsetail movement are normal, chromatin remodeling at ade6-M26, a recombination hotspot, which is prerequisite for subsequent DSB formation at this locus, is not observed in hsk1-89. These results indicate unique and essential roles of Hsk1 kinase in the initiation of meiotic recombination and meiosis.Cdc7-related kinase ͉ checkpoint control ͉ chromatin remodeling ͉ meiosis ͉ meiotic recombination A lthough recent studies revealed the presence of a number of conserved factors involved in mitotic DNA replication (1), it is largely unknown whether they play roles in meiotic replication and recombination (2, 3). Studies in fission and budding yeasts indicated essential roles of Cdc2 kinase (1) and Clb5-and Clb6-dependent Cdc28 kinase (4), respectively, in premeiotic DNA replication. Orc, Cdc18, and MCM are also required for premeiotic DNA synthesis (3, 5), although their requirement may not be identical to that during mitotic replication (2). It is not known whether initiation is regulated by a common mechanism or the same set of replication origins is used during premeiotic S phase. In budding yeast, strong coupling of DNA replication and meiotic recombination has been shown (6-9).Cdc7 kinase plays an essential role in firing replication origins during mitotic growth (10, 11). It was reported previously that meiotic recombination frequency is reduced, whereas premeiotic DNA replication proceeds, in the budding yeast cdc7 ts mutants and that Cdc7 may play a role in synaptonemal complex formation during meiosis, a step stabilizing homologous pairing during meiotic recombination (12,13), but the precise meiotic roles of Cdc7 have remained elusive. We report here that Hsk1, the fission yeast homologue of Cdc7 kinase, is required for efficient meiotic recombination and meiotic nuclear division. During meiosis, Hsk1 is required specifically for formation of dsDNA breaks (DSBs), an early event for meiotic recombinatio...

“…A high level of homologous recombination occurs after DNA replication but before the first meiotic nuclear division [meiosis I (MI)] (1,(3)(4)(5)(6)(7). Progression through meiosis is controlled by orchestration of the expression of various meiotic genes (8)(9)(10).…”

mentioning

confidence: 99%

Mei4p coordinates the onset of meiosis I by regulating cdc25 ⁺ in fission yeast

Murakami-Tonami

Yamada‐Namikawa

Tochigi

et al. 2007

The kinase Cdc2p is a central regulator of entry into and progression through nuclear division during mitosis and meiosis in eukaryotes. Cdc2p is activated at the onset of mitosis by dephosphorylation on tyrosine-15, the phosphorylation status of which is determined mainly by the kinase Wee1p and the phosphatase Cdc25p. In fission yeast, the forkhead-type transcription factor Mei4p is required for expression of many genes during meiosis, with mei4 mutant cells arresting before meiosis I. The mechanism of cell cycle arrest in mei4 cells has remained unknown, however. We now show that cdc25 ؉ is an important target of Mei4p in control of entry into meiosis I. Forced dephosphorylation of Cdc2p on tyrosine-15 thus induced meiosis I in mei4 mutant cells without a delay, although no spores were formed. We propose that Mei4p acts as a rate-limiting regulator of meiosis I by activating cdc25 ؉ transcription in coordination with other meiotic events.cell cycle ͉ transcription