Abstract
RNA-DNA hybrids are often associated with genome instability and also function as a cellular regulator in many biological processes. In this study, we show that accumulated RNA-DNA hybrids cause multiple defects in budding yeast meiosis, including decreased sporulation efficiency and spore viability. Further analysis shows that these RNA-DNA hybrid foci colocalize with RPA/Rad51 foci on chromosomes. The efficient formation of RNA-DNA hybrid foci depends on Rad52 and ssDNA ends of meiotic DNA double-strand breaks (DSBs), and their number is correlated with DSB frequency. Interestingly, RNA-DNA hybrid foci and recombination foci show similar dynamics. The excessive accumulation of RNA-DNA hybrids around DSBs competes with Rad51/Dmc1, impairs homolog bias, and decreases crossover and noncrossover recombination. Furthermore, precocious removal of RNA-DNA hybrids by RNase H1 overexpression also impairs meiotic recombination similarly. Taken together, our results demonstrate that RNA-DNA hybrids form at ssDNA ends of DSBs to actively regulate meiotic recombination.
Highlights
Meiosis is a specialized cell division to generate haploid gametes
We demonstrate that RNA-DNA hybrids were primarily formed at single-strand DNA (ssDNA) ends of meiotic double-strand breaks (DSBs)
To investigate the roles of RNA-DNA hybrids in meiotic DSB repair, these hybrids were examined in the surface spread of meiotic nuclei (Figures 1A, 1B, and S1)
Summary
Meiosis is a specialized cell division to generate haploid gametes. During meiosis, DNA undergoes one replication, followed by segregation of homologous chromosomes (homologs) in meiosis I and sister chromatids in meiosis II. A central feature of meiosis is the repair of DNA double-strand breaks (DSBs) using homologs as templates to generate crossovers (COs) (Hunter, 2015; Zickler and Kleckner, 2015). Meiotic recombination is initiated from Spo complex catalyzed DSBs (Keeney et al, 1997, 2014) After endonucleolytic cleavage, both Spo and its covalently bound DNA oligos are removed by the Mre11-Rad50-Xrs2/Nbs complex (MRX) to produce short 30 single-strand DNA (ssDNA), which are further resected by the Exo exonuclease (Borde, 2007; Zakharyevich et al, 2010; Garcia et al, 2011). The process of meiotic recombination is still not well understood, especially regarding how homolog bias and CO formation are ensured
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