Spirek, M. | Search bioRxiv

bioRxiv2026

BRC-2/BRCA2-RIPR-1 mediated constraints on homologous recombination execution are spatiotemporally regulated during meiosis

Homologous recombination-dependent processing of meiotic double-strand breaks is crucial to generate functional gametes. The breast and ovarian cancer susceptibility gene BRCA2 is essential for the loading of RAD51-DMC1 recombinases at DNA breaks to allow accurate repair. Here, we identify the novel protein RIPR-1 as a binding partner of Caenorhabditis elegans BRC-2/BRCA2. RIPR-1 and BRC-2 form an obligate complex both in vitro and in vivo and display interdependent loading in developing oocytes. Loss of ripr-1 results in the complete destabilization of BRC-2, while brc-2 is only partially required to preserve RIPR-1 stability. Strikingly, we found a dramatic accumulation of RAD-51 in late pachytene cells of both ripr-1 and brc-2 nulls, unveiling a BRCA2-independent pathway for recruitment of RAD-51 at resected meiotic DNA breaks. RIPR-1 enhances BRC-2 binding to single-stranded DNA and unlike the individual components, the assembled RIPR-1-BRC-2 complex can also bind double-stranded DNA in vitro. Surprisingly, we observe that RAD-51-dependent crossover designation still occurs in absence of RIPR-1-BRC-2, indicating partial, and stage-dependent constraints on homologous recombination execution. Altogether, our work identifies a novel BRC-2 interactor and sheds new light on HR-mediated regulation of DNA repair during meiosis.

Cell Biology↗

bioRxiv2020

Antibiotic-induced DNA damage results in a controlled loss of pH homeostasis and genome instability

Extracellular pH has been assumed to play little if any role in how bacteria respond to antibiotics and antibiotic resistance development. Here, we show that the intracellular pH of Escherichia coli equilibrates to the environmental pH following antibiotic treatment. We demonstrate that this allows the environmental pH to influence the transcription of various DNA damage response genes and physiological processes such as filamentation. Using purified RecA and a known pH-sensitive mutant variant RecA K250R we show how pH can affect the biochemical activity of a protein central to control of the bacterial DNA damage response system. Finally, two different mutagenesis assays indicate that environmental pH affects antibiotic resistance development. Specifically, at environmental pHs greater than six we find that mutagenesis plays a significant role in producing antibiotic resistant mutants. At pHs less than or equal to 6 the genome appears more stable but extensive filamentation is observed, a phenomenon that has previously been linked to increased survival in the presence of macrophages.

microbiology↗