Dr. Pietro Pichierri - RAD52 a new factor balancing fork reversal and repriming at perturbed replication forks

Pietro Pichierri

Istituto Superiore di Sanità, Rome, Italy

RAD52 a new factor balancing fork reversal and repriming at perturbed replication forks

Rad52 (Radiation sensitive 52) is a highly conserved protein involved in DNA damage repair. In yeast, Rad52 is essential for all types of recombination-mediated DSB repair while, in higher eukaryotes, BRCA2 took over most of the recombination-related functions and RAD52 remains critical only for single-strand annealing.

In humans, RAD52 contributes to the rescue of perturbed replication forks collaborating with the MUS81 complex when replication checkpoint or BRCA2 is defective and it has been recently involved in limiting excessive reversion of the fork that would result in pathological strand degradation irrespective of the BRCA2 status. My talk will illustrate novel functions of RAD52 during the response to perturbed replication in human cells, summarizing our recently published works showing how it can limit excessive fork reversal and it will show you unpublished results indicating that level of RAD52 may contribute to channeling perturbed replication forks through distinct recovery mechanisms.

In particular, our data would suggest that in response to hydroxyurea-mediated replication fork arrest, inhibition of RAD52 induces the accumulation of parental DNA gaps that derive from increased recruitment of DNA polymerase alpha (Polα) and that RAD52 deficiency stimulates Polα, but not PrimPol-mediated replication repriming. In contrast, the overexpression of RAD52 dramatically increases PrimPol-dependent accumulation of parental DNA gaps. Moreover, our data show that Polα recruitment depends on the function of RAD51 in this context. Collectively, this could explain the increase of under-replicated regions of DNA when RAD52 is deregulated that may result toxic if not correctly repaired.

Selected references

• Hanamshet K, Mazina OM, Mazin AV. Reappearance from Obscurity: Mammalian Rad52 in Homologous Recombination. Genes (Basel) 2016 7(9):63
• Kondratick CM, Washington MT, Spies M. Making choices: DNA replication fork recovery mechanisms. Semin Cell Dev Biol 2021 113:27-37
• Hengel SR, Malacaria E, Folly da Silva Constantino L, Bain FE, Diaz A, Koch BG, Yu L, Wu M, Pichierri P, Spies MA, Spies M. Small-molecule inhibitors identify the RAD52-ssDNA interaction as critical for recovery from replication stress and for survival of BRCA2 deficient cells. Elife 2016 5:e14740
• Murfuni I, Basile G, Subramanyam S, Malacaria E, Bignami M, Spies M, Franchitto A, Pichierri P. Survival of the replication checkpoint deficient cells requires MUS81-RAD52 function. PLoS Genet 2013 9(10):e1003910
• Malacaria E, Pugliese GM, Honda M, Marabitti V, Aiello FA, Spies M, Franchitto A, Pichierri P. RAD52 prevents excessive replication fork reversal and protects from nascent strand degradation. Nat Commun 2019 10(1):1412