Serine ADP-Ribosylation Depends on HPF1

Abstract

SummaryADP-ribosylation (ADPr) regulates important patho-physiological processes through its attachment to different amino acids in proteins. Recently, by precision mapping on all possible amino acid residues, we identified histone serine ADPr marks in the DNA damage response. However, the biochemical basis underlying this serine modification remained unknown. Here we report that serine ADPr is strictly dependent on histone PARylation factor 1 (HPF1), a recently identified regulator of PARP-1. Quantitative proteomics revealed that serine ADPr does not occur in cells lacking HPF1. Moreover, adding HPF1 to in vitro PARP-1/PARP-2 reactions is necessary and sufficient for serine-specific ADPr of histones and PARP-1 itself. Three endogenous serine ADPr sites are located on the PARP-1 automodification domain. Further identification of serine ADPr on HMG proteins and hundreds of other targets indicates that serine ADPr is a widespread modification. We propose that O-linked protein ADPr is the key signal in PARP-1/PARP-2-dependent processes that govern genome stability.

ADP-Ribosylation Goes Normal: Serine as the Major Site of the Modification

“…Most notably, high-mobility group proteins associated with chromatin are among the prime serine ADP-ribosylation targets. Reprocessing of the highquality proteomics datasets published by others not only confirmed the PARylation targets found by Ahel and Matic themselves (Bonfiglio et al, 2017), but also provided more than 250 additional Ser-ADPr sites.…”

“…Significantly, no other ADPr-sites were detected in vivo, which immediately invites the audacious idea that serine is the true native site of ADP-ribosylation, suggesting that the other ADPr-amino acids are merely an in vitro artifact. In their Molecular Cell paper (Bonfiglio et al, 2017), the authors expand the studies of serine PARylation beyond histones to other proteins and strengthen the evidence that ADPr-serine is a widespread PARP-1-mediated protein modification (Figure 1). Significantly, the biochemistry behind the PARylation of serine is also uncovered through the described research.…”

“…Proteins containing adenosine diphosphate ribosylserine as a posttranslational modification are widespread and formed via HPF1-assisted, PARP-1-mediated PARylation as Bonfiglio et al (2017) report in a recent issue of Molecular Cell.…”

“…It is also somewhat enigmatic how the same transferase is capable of catalyzing different chemical transformations. In a recent issue of Molecular Cell, an important joint paper by the Ahel and Matic groups (Bonfiglio et al, 2017) reports on the prevalence of ADP-ribosylation at serine and, by doing so, brings a sense of normality to the ADP-ribosylation field. Methodologically, the work capitalizes on a clever mass-spectrometry-based proteomics approach that uses partial trypsin digestion of proteins (partial FASP) combined with a mild MS-MS fragmentation technique (electron-transfer dissociation [ETD]) (Leidecker et al, 2016).…”

ADP-Ribosylation Reactions in Animals, Plants, and Bacteria

“…Dr. Hottiger took the stage to present the extraordinary findings obtained by the immunoseparation of PARylated proteins using a mutant Macrodomain [28][29][30]. The most exciting finding in recent months was the ADP ribosylation at serine residues [31], in addition to lysine being found to serve as an ADP-ribose acceptor site.…”