Blazickova, J. | bioRxiv Science

bioRxiv2024

Distinct intersecting pathways link homolog pairing to initiation of meiotic chromosome synapsis

Faithful meiotic segregation requires pairwise alignment of the homologous chromosomes and Synaptonemal Complex assembly (SC) at their interface. Here, we investigate on new factors that promote and coordinate these events during C. elegans meiosis. We identify BRA-2 (BMP Receptor Associated family member 2) as an interactor of HIM-17, previously shown to promote double-strand break formation. We found that loss of bra-2 specifically impairs synapsis licensing without affecting homologs recognition, SC maintenance or chromosome movement. Double mutant analysis revealed a previously unrecognized role for HIM-17 in promoting homolog pairing under dysfunctional SC assembly, without perturbing nuclear envelope recruitment of factors required for chromosome movement. We provide evidence that bra-2 and him-17 act in distinct pathways, exerting partially redundant functions in SC licensing, as well as separable roles in regulating homologs pairing. Altogether, our findings unveil novel mechanisms that ensure stabilization of homologous chromosome interaction via SC licensing upon homology assessment.

cell biology↗

bioRxiv2022

PARG establishes a functional module with BRCA1-BARD1 that controls DNA repair pathway choice during gametogenesis

During meiosis, accurate chromosome segregation relies on the formation of programmed DNA double-strand breaks (DSBs). These are in turn repaired by homologous recombination (HR), generating physical attachments between the parental chromosomes called crossovers (COs). Fewer breaks yield recombinant outcomes, while CO-independent mechanisms are employed for repairing the majority of lesions. The balance between different repair pathways is crucial to ensure genome fidelity and to preserve its integrity. We show that Caenorhabditis elegans BRC-1/BRCA1-BRD-1/BARD1 and PARG-1/PARG form a complex in vivo, that is essential for accurate DNA repair in the germline. Contemporary depletion of BRC-1 and PARG-1 causes synthetic lethality due to reduced CO formation and impaired DSB repair, as evidenced by hindered RPA-1 removal and presence of aberrant chromatin bodies in diakinesis nuclei, whose formation depends on spo-11 function. These factors largely co-localize and undergo independent loading in developing oocytes, consistent with operating in different pathways. Abrogation of KU- or Theta-mediated end joining elicits opposite effects in brc-1; parg-1 doubles, highlighting differential involvement of DNA repair pathways and suggesting a profound impact in influencing DNA repair pathway choice by BRC-1-PARG-1. Importantly, lack of PARG-1 catalytic activity suppresses untimely accumulation of RAD-51 foci in brc-1 mutants but is only partially required to maintain fertility. Altogether, our data show that BRC-1/BRD-1-PARG-1 joined function is essential to keep genome integrity in meiotic cells by regulating multiple DNA repair pathways.

genetics↗