The Caenorhabditis elegans Homolog of Gen1/Yen1 Resolvases Links DNA Damage Signaling to DNA Double-Strand Break Repair

Aymeric P Bailly,Julie Hall,Anton Gartner,Shawn Ahmed,David M J Lilley,Alasdair Freeman,Arno Alpi,Anne-Cécile Déclais,Tim Schedl

doi:10.1371/journal.pgen.1001025

Aymeric P Bailly, Julie Hall + Show 7 more

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https://doi.org/10.1371/journal.pgen.1001025

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Abstract

DNA double-strand breaks (DSBs) can be repaired by homologous recombination (HR), which can involve Holliday junction (HJ) intermediates that are ultimately resolved by nucleolytic enzymes. An N-terminal fragment of human GEN1 has recently been shown to act as a Holliday junction resolvase, but little is known about the role of GEN-1 in vivo. Holliday junction resolution signifies the completion of DNA repair, a step that may be coupled to signaling proteins that regulate cell cycle progression in response to DNA damage. Using forward genetic approaches, we identified a Caenorhabditis elegans dual function DNA double-strand break repair and DNA damage signaling protein orthologous to the human GEN1 Holliday junction resolving enzyme. GEN-1 has biochemical activities related to the human enzyme and facilitates repair of DNA double-strand breaks, but is not essential for DNA double-strand break repair during meiotic recombination. Mutational analysis reveals that the DNA damage-signaling function of GEN-1 is separable from its role in DNA repair. GEN-1 promotes germ cell cycle arrest and apoptosis via a pathway that acts in parallel to the canonical DNA damage response pathway mediated by RPA loading, CHK1 activation, and CEP-1/p53–mediated apoptosis induction. Furthermore, GEN-1 acts redundantly with the 9-1-1 complex to ensure genome stability. Our study suggests that GEN-1 might act as a dual function Holliday junction resolvase that may coordinate DNA damage signaling with a late step in DNA double-strand break repair.

Highlights

The correct maintenance and duplication of genetic information is constantly challenged by genotoxic stress
Coordination of DNA repair with cell cycle progression and apoptosis is a central task of the DNA damage response machinery
Using forward genetics, we identified a Caenorhabditis elegans dual function DNA double-strand break repair and DNA damage signaling protein orthologous to the human GEN1 Holliday junction resolving enzyme

Summary

Introduction

The correct maintenance and duplication of genetic information is constantly challenged by genotoxic stress. Following DSB formation, broken ends are resected in a 59 to 39 direction to generate 39 single-strand overhangs [1] These tails are coated by RPA1 molecules, which in turn are thought to lead to the recruitment of the ATR checkpoint kinase [2]. Annealing of the 39 single-stranded tail of the second resected DNA end to the displaced donor DNA strand (second end capture), and DNA ligation lead to the formation of a double Holliday junction (dHJ) intermediate (for a review, see [12]) This dHJ must be resolved either through cleavage by Holliday junction (HJ)-resolving enzymes or through ‘‘dissolution’’ by the combined activity of the Blooms helicase and topoisomerase III [13,14]

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