Archaeal Hel308 suppresses recombination through a catalytic switch that controls DNA annealing

Lever, Rebecca J., Simmons, Emily, Gamble-Milner, Rebecca, Buckley, Ryan J., Harrison, Catherine, Parkes, Ashley J., Mitchell, Laura, Gausden, Jacob A., Skulj, Sanja, Bertosa, Branimir, Bolt, Edward L. and Allers, Thorsten 2023. Archaeal Hel308 suppresses recombination through a catalytic switch that controls DNA annealing. Nucleic Acids Research 51 (16) , pp. 8563-8574. 10.1093/nar/gkad572

PDF - Published Version Available under License Creative Commons Attribution. Download (1MB)

Abstract

Hel308 helicases promote genome stability in archaea and are conserved in metazoans, where they are known as HELQ. Their helicase mechanism is well characterised, but it is unclear how they specifically contribute to genome stability in archaea. We show here that a highly conserved motif of Hel308/HELQ helicases (motif IVa, F/YHHAGL) modulates both DNA unwinding and a newly identified strand annealing function of archaeal Hel308. A single amino acid substitution in motif IVa results in hyper-active DNA helicase and annealase activities of purified Hel308 in vitro. All-atom molecular dynamics simulations using Hel308 crystal structures provided a molecular basis for these differences between mutant and wild type Hel308. In archaeal cells, the same mutation results in 160000-fold increased recombination, exclusively as gene conversion (non-crossover) events. However, crossover recombination is unaffected by the motif IVa mutation, as is cell viability or DNA damage sensitivity. By contrast, cells lacking Hel308 show impaired growth, increased sensitivity to DNA cross-linking agents, and only moderately increased recombination. Our data reveal that archaeal Hel308 suppresses recombination and promotes DNA repair, and that motif IVa in the RecA2 domain acts as a catalytic switch to modulate the separable recombination and repair activities of Hel308.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Schools > Medicine
Publisher:	Oxford University Press
ISSN:	0305-1048
Date of First Compliant Deposit:	22 October 2025
Date of Acceptance:	23 June 2023
Last Modified:	22 Oct 2025 09:15
URI:	https://orca.cardiff.ac.uk/id/eprint/181820

Actions (repository staff only)

Edit Item