Multiple 9-1-1 complexes promote homolog synapsis, DSB repair, and ATR signaling during mammalian meiosis.

Catalina Pereira,Matthew Z Guo,Charlton Tsai,Heinz Jacobs,Gerardo A Arroyo-Martinez,Emma R Kelly,Raimundo Freire,Carl J Schiltz,Paula E Cohen ,Niek J De Wit ,Jennie R Sims ,Kathryn J Grive ,Nathan L Clark ,Miguel A Brieño‐Enríquez ,Vitor M Faça ,Amy M Lyndaker ,James M A Turner ,Michael S Downey ,Marcus B Smolka ,Shantha K Mahadevaiah ,Robert S Weiss

doi:10.7554/elife.68677

Abstract

DNA damage response mechanisms have meiotic roles that ensure successful gamete formation. While completion of meiotic double-strand break (DSB) repair requires the canonical RAD9A-RAD1-HUS1 (9A-1-1) complex, mammalian meiocytes also express RAD9A and HUS1 paralogs, RAD9B and HUS1B, predicted to form alternative 9-1-1 complexes. The RAD1 subunit is shared by all predicted 9-1-1 complexes and localizes to meiotic chromosomes even in the absence of HUS1 and RAD9A. Here, we report that testis-specific disruption of RAD1 in mice resulted in impaired DSB repair, germ cell depletion, and infertility. Unlike Hus1 or Rad9a disruption, Rad1 loss in meiocytes also caused severe defects in homolog synapsis, impaired phosphorylation of ATR targets such as H2AX, CHK1, and HORMAD2, and compromised meiotic sex chromosome inactivation. Together, these results establish critical roles for both canonical and alternative 9-1-1 complexes in meiotic ATR activation and successful prophase I completion.

Highlights

DNA damage response (DDR) mechanisms protect genomic integrity by sensing and repairing DNA lesions or initiating apoptosis when lesions are unrepairable (Blackford and Jackson, 2017)
Phylogenetic analysis suggested that the duplication event generating Rad9a and Rad9b occurred prior to the evolution of bony fish ancestors (Danio rerio), whereas the single-exon Hus1b gene likely arose after a retrocopy duplication event later in evolution in mammals
We report that testis-s pecific RAD1 loss results in homolog asynapsis, compromised double-s trand break (DSB) repair, faulty ATR signaling, and impaired meiotic silencing (Figure 6G)

Summary

Introduction

DNA damage response (DDR) mechanisms protect genomic integrity by sensing and repairing DNA lesions or initiating apoptosis when lesions are unrepairable (Blackford and Jackson, 2017). Double-strand DNA breaks (DSBs) are considered to be the most toxic form of DNA damage, meiotic recombination relies on SPO11-induced DSBs for homologous chromosomes to synapse, exchange genetic material, and properly segregate at the first meiotic division (Bolcun-F ilas et al, 2014; Gray and Cohen, 2016). Leptonema, axial elements containing SC protein 3 (SYCP3) form along condensed chromosomes (Page and Hawley, 2004). The DNA damage marker, γH2AX, accumulates during leptonema as chromosomes experience SPO11-induced DSBs. Progression into zygonema is characterized by the pairing and synapsis of chromosomes, marked by the presence of the central element protein SC protein 1 (SYCP1). Breakdown of the SC marks the final stage in prophase I, diakinesis

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