In response to DNA damage, the histone PARylation factor 1 (HPF1) regulates PARP1/2 activity, facilitating serine ADP-ribosylation of chromatin-associated factors. While PARP1/2 are known for their role in DNA single-strand break repair (SSBR), the significance of HPF1 in this process remains unclear. Here, we investigated the impact of HPF1 deficiency on cellular survival and SSBR following exposure to various genotoxins. We found that HPF1 loss did not generally increase cellular sensitivity to agents that typically induce DNA single-strand breaks (SSBs) repaired by PARP1. SSBR kinetics in HPF1-deficient cells were largely unaffected, though its absence partially influenced the accumulation of SSB intermediates after exposure to specific genotoxins in certain cell lines, likely due to altered ADP-ribosylation of chromatin. Despite reduced serine mono-ADP-ribosylation, HPF1-deficient cells maintained robust poly-ADP-ribosylation at SSB sites, possibly reflecting PARP1 auto-poly-ADP-ribosylation at non-serine residues. Notably, poly-ADP-ribose chains were sufficient to recruit the DNA repair factor XRCC1, which may explain the relatively normal SSBR capacity in HPF1-deficient cells. These findings suggest that HPF1 and histone serine ADP-ribosylation are largely dispensable for PARP1-dependent SSBR in response to genotoxic stress, highlighting the complexity of mechanisms that maintain genomic stability and chromatin remodeling.

• MeSH
• Cell Line MeSH
• Chromatin metabolism   MeSH
• DNA-Binding Proteins metabolism   genetics   MeSH
• Histones metabolism   MeSH
• Nuclear Proteins metabolism   genetics   MeSH
• DNA Breaks, Single-Stranded * MeSH
• Humans MeSH
• DNA Repair * MeSH
• Poly ADP Ribosylation MeSH
• Poly (ADP-Ribose) Polymerase-1 * metabolism   genetics   MeSH
• Poly(ADP-ribose) Polymerases metabolism   genetics   MeSH
• X-ray Repair Cross Complementing Protein 1 metabolism   genetics   MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH

Poly(ADP-ribosyl)ation is a reversible post-translational modification synthetized by ADP-ribose transferases and removed by poly(ADP-ribose) glycohydrolase (PARG), which plays important roles in DNA damage repair. While well-studied in somatic tissues, much less is known about poly(ADP-ribosyl)ation in the germline, where DNA double-strand breaks are introduced by a regulated program and repaired by crossover recombination to establish a tether between homologous chromosomes. The interaction between the parental chromosomes is facilitated by meiotic specific adaptation of the chromosome axes and cohesins, and reinforced by the synaptonemal complex. Here, we uncover an unexpected role for PARG in coordinating the induction of meiotic DNA breaks and their homologous recombination-mediated repair in Caenorhabditis elegans. PARG-1/PARG interacts with both axial and central elements of the synaptonemal complex, REC-8/Rec8 and the MRN/X complex. PARG-1 shapes the recombination landscape and reinforces the tightly regulated control of crossover numbers without requiring its catalytic activity. We unravel roles in regulating meiosis, beyond its enzymatic activity in poly(ADP-ribose) catabolism.

• MeSH
• Cell Nucleus metabolism   MeSH
• Caenorhabditis elegans genetics   metabolism   MeSH
• DNA metabolism   MeSH
• DNA Breaks, Double-Stranded * MeSH
• Glycoside Hydrolases genetics   metabolism   MeSH
• Nuclear Proteins genetics   metabolism   MeSH
• DNA Repair physiology   MeSH
• Poly ADP Ribosylation MeSH
• Poly Adenosine Diphosphate Ribose metabolism   MeSH
• Protein Processing, Post-Translational MeSH
• Caenorhabditis elegans Proteins genetics   metabolism   MeSH
• Germ Cells MeSH
• Animals MeSH
• Check Tag
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Research Support, N.I.H., Extramural MeSH