Piberger, Ann LizaBowry, AkhilKelly, Richard D WWalker, Alexandra KGonzalez-Acosta, DanielBailey, Laura JDoherty, Aidan JMéndez, JuanMorris, Joanna RBryant, Helen EPetermann, EvaMendez, Juan2021-03-092021-03-092020-11-11Nat Commun.2020 ;11(1):5863.http://hdl.handle.net/20.500.12105/12177Stalled replication forks can be restarted and repaired by RAD51-mediated homologous recombination (HR), but HR can also perform post-replicative repair after bypass of the obstacle. Bulky DNA adducts are important replication-blocking lesions, but it is unknown whether they activate HR at stalled forks or behind ongoing forks. Using mainly BPDE-DNA adducts as model lesions, we show that HR induced by bulky adducts in mammalian cells predominantly occurs at post-replicative gaps formed by the DNA/RNA primase PrimPol. RAD51 recruitment under these conditions does not result from fork stalling, but rather occurs at gaps formed by PrimPol re-priming and resection by MRE11 and EXO1. In contrast, RAD51 loading at double-strand breaks does not require PrimPol. At bulky adducts, PrimPol promotes sister chromatid exchange and genetic recombination. Our data support that HR at bulky adducts in mammalian cells involves post-replicative gap repair and define a role for PrimPol in HR-mediated DNA damage tolerance.engSMURhttp://creativecommons.org/licenses/by-nc-sa/4.0/4-Nitroquinoline-1-oxide7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxideBenz(a)AnthracenesCell LineDNA AdductsDNA PrimaseDNA, Single-StrandedDNA-Directed DNA PolymeraseHomologous RecombinationHumansMultifunctional EnzymesQuinolonesRad51 RecombinaseSingle Molecule ImagingSister Chromatid ExchangeAtribución-NoComercial-CompartirIgual 4.0 Internacional33203852111586310.1038/s41467-020-19570-72041-1723Nature communicationsopen access