Xrs2 C-terminus mediates Tel1-dependent meiotic double-strand break interference

Abstract

During meiosis, the programmed formation of DNA double-strand breaks (DSBs) by Spo11, a conserved topoisomerase II-like protein, initiates homologous recombination that leads to crossovers between homologous chromosomes, essential for accurate chromosome segregation and genome evolution. The DSB number, distribution and timing of formation are regulated during meiosis to ensure crossing over on all chromosomes and prevent genome instability. In S. cerevisiae, DSB interference suppresses the coincident formation of DSBs in neighboring hotspots through a Tel1/ATM dependent mechanism that remains unexplored. Here, we demonstrate that Tel1 is recruited to meiotic DSB hotspots and chromosomal axis sites in a DSB-dependent manner. This supports the tethered loop-axis complex (TLAC) model that postulates meiotic DSBs are formed within the chromosome axis environment. Tel1 recruitment to meiotic DSBs, DSB interference and the meiotic DNA damage checkpoint are all dependent on the C-terminal moiety of Xrs2, known to mediate Tel1-Xrs2 interaction in vegetative cells. However, mutation of the Xrs2 FxF/Y motif, known to stabilize Tel1 interaction with Xrs2, does not affect DSBs interference but abolishes the Tel1-dependent DNA damage checkpoint. Altogether, this work uncovers the dynamic association of Tel1 with meiotic chromosomes and highlights the critical role of its interaction with Xrs2 in fine-tuning both the meiotic DNA damage checkpoint and DSB interference. AUTHOR SUMMARYDuring meiosis, a special type of cell division that produces gametes, cells intentionally break their own DNA at preferred genomic sites (hotspots) to help shuffle genetic material between chromosomes. The repair process of those breaks, called homologous recombination, is crucial for genetic diversity and for ensuring chromosomes are distributed correctly to gametes. The number and location of DNA breaks are tightly controlled to prevent errors that could affect genetic stability. In the yeast model S. cerevisiae, a protein called Tel1 (the counterpart of ATM in mammals, a DNA damage sensor) helps limit the number of breaks per cell. Our research shows that Tel1 is recruited to DNA breaks and to specific chromosome structures (called axis), supporting the idea that DNA breaks happen within the axis environment. We also found that recruitment of Tel1 to DNA breaks depends on another protein, Xrs2. This interaction is crucial to limit further DNA breaks formation and to arrest cell cycle progression in response to DNA breaks. Overall, these findings shed light on Tel1 dynamics on meiotic chromosomes, and reveal how Tel1 and Xrs2 work together to maintain genetic stability during meiosis, a process essential for healthy reproduction and evolution.