Villoria, M. T. | Search bioRxiv

bioRxiv2025

PP4Psy2 regulates Rrm3 and Pif1 helicases to facilitate DSB resection across tandem retrotransposons

Double-strand break repair is a tightly regulated process that relies on the coordinated activity of kinase and phosphatase complexes. Here we show that the PP4 phosphatase regulatory subunits, Psy2 and Psy4, act as positive and negative regulators of the holoenzyme during DSB repair. Cdk-dependent phosphorylation of Psy2 is crucial for DSB repair but is not required for DNA damage checkpoint inactivation. Lack of Psy2 leads to an asymmetric resection defect on one side of the DSB, a defect that is alleviated by expressing a phosphodeficient H2A variant or by depleting the checkpoint adaptor Rad9. This resection asymmetry is associated to the presence of tandem retrotransposons proximal to the DSB site, underlining the role of PP4Psy2 in stimulating resection across repetitive heterochromatic regions. PP4Psy2 support resection progression through paired transposable elements by reducing the phosphorylation state of Pif1 and Rrm3 helicases during the DSB response. These findings provide a comprehensive framework for the role of PP4Psy2 in resection-mediated DSB repair, highlighting its function in coordinating helicases activity to preserve genomic stability in response to DNA damage.

molecular biology↗

bioRxiv2018

PP4 phosphatase cooperates in recombinational DNA repair by enhancing double-strand break end resection

The role of Rad53 in response to a DNA lesion is central for the accurate orchestration of the DNA damage response. Rad53 activation relies on its phosphorylation by the Mec1 kinase and its own auto-phosphorylation in a manner dependent on the adaptor Rad9. While the mechanism behind Rad53 phosphorylation and activation has been well documented, less is known about the processes that counteract its kinase activity during the response to DNA damage. Here, we describe that PP4 phosphatase dephosphorylates Rad53 during the repair of a double-strand break, a process that impacts on the phosphorylation status of multiple factors involved in the DNA damage response. PP4-dependent Rad53 dephosphorylation stimulates DNA end resection by relieving the negative effect that Rad9 exerts over the Sgs1/Dna2 exonuclease complex. Consequently, elimination of PP4 activity affects DNA resection and repair by single-strand annealing, defects that are bypassed by reducing the hyper-phosphorylation state of Rad53 observed in the absence of the phosphatase. These results confirm that Rad53 is one of the main targets of PP4 during the repair of a DNA lesion and demonstrate that the attenuation of its kinase activity during the initial steps of the repair process is essential to efficiently enhance recombinational DNA repair pathways that depend on long-range resection.

molecular biology↗