Phosphoregulation of DSB-1 mediates control of meiotic double-strand break activity

Abstract

In the first meiotic cell division, proper segregation of chromosomes in most organisms depends on chiasmata, exchanges of continuity between homologous chromosomes that originate from the repair of programmed double-strand breaks (DSBs) catalyzed by the Spo11 endonuclease. Since DSBs can lead to irreparable damage in germ cells, while chromosomes lacking DSBs also lack chiasmata, the number of DSBs must be carefully regulated to be neither too high nor too low. Here, we show that in Caenorhabditis elegans, meiotic DSB levels are controlled by the phosphoregulation of DSB-1, a homolog of the yeast Spo11 cofactor Rec114, by the opposing activities of PP4PPH-4.1 phosphatase and ATRATL-1 kinase. Increased DSB-1 phosphorylation in pph-4.1 mutants correlates with reduction in DSB formation, while prevention of DSB-1 phosphorylation drastically increases the number of meiotic DSBs both in pph-4.1 mutants and in the wild-type background. C. elegans and its close relatives also possess a diverged paralog of DSB-1, called DSB-2, and loss of dsb-2 is known to reduce DSB formation in oocytes with increasing age. We show that the proportion of the phosphorylated, and thus inactivated, form of DSB-1 increases with age and upon loss of DSB-2, while non-phosphorylatable DSB-1 rescues the age-dependent decrease in DSBs in dsb-2 mutants. These results suggest that DSB-2 evolved in part to compensate for the inactivation of DSB-1 through phosphorylation, to maintain levels of DSBs in older animals. Our work shows that PP4PPH-4.1, ATRATL-1, and DSB-2 act in concert with DSB-1 to promote optimal DSB levels throughout the reproductive lifespan.

Aging and sperm signals alter DNA break formation and repair in the C. elegans germline

“…Thus, we suggest that DSB induction in aged germlines is primarily repressed by signals caused from sperm depletion rather than reproductive aging, mating-induced signaling, or exposure to males. Multiple mutants in C. elegans have been reported to exhibit age-dependent decline in meiotic DSB induction [30,44,45]. Our research raises the possibility that these proteins may mediate or respond to signals from sperm.…”

“…Sperm depletion, but not absence of sperm, reduces DAF-16 nuclear localization in the intestine, indicating that loss of sperm has tissue-nonautonomous effects on IIS [49]. Notably, a recent study found that PP4 also maintains DSB induction in the C. elegans germline by promoting the dephosphorylation of the Rec114 homolog DSB-1 [45]. From this evidence, we propose that the influence of sperm depletion on DSB induction may be mediated through the IIS pathway.…”

“…Multiple mutants in C . elegans have been reported to exhibit age-dependent decline in meiotic DSB induction [ 30 , 44 , 45 ]. Our research raises the possibility that these proteins may mediate or respond to signals from sperm.…”

“…Notably, a recent study found that PP4 also maintains DSB induction in the C . elegans germline by promoting the dephosphorylation of the Rec114 homolog DSB-1 [ 45 ]. From this evidence, we propose that the influence of sperm depletion on DSB induction may be mediated through the IIS pathway.…”

Recruitment of Polo-like kinase couples synapsis to meiotic progression via inactivation of CHK-2

“…Auxin-mediated protein depletion was performed as previously described (Guo et al, 2022; Zhang et al, 2015). Briefly, worms were transferred to bacteria-seeded plates containing 1 mM indole-3-acetic acid (Acros Organics, Cat #122160250) and incubated for the indicated time periods before analysis.…”