Ubiquitin Modification by the E3 Ligase/ADP-Ribosyltransferase Dtx3L/Parp9

Mol Cell. 2017 May 18;66(4):503-516.e5. doi: 10.1016/j.molcel.2017.04.028.

Abstract

ADP-ribosylation of proteins is emerging as an important regulatory mechanism. Depending on the family member, ADP-ribosyltransferases either conjugate a single ADP-ribose to a target or generate ADP-ribose chains. Here we characterize Parp9, a mono-ADP-ribosyltransferase reported to be enzymatically inactive. Parp9 undergoes heterodimerization with Dtx3L, a histone E3 ligase involved in DNA damage repair. We show that the Dtx3L/Parp9 heterodimer mediates NAD+-dependent mono-ADP-ribosylation of ubiquitin, exclusively in the context of ubiquitin processing by E1 and E2 enzymes. Dtx3L/Parp9 ADP-ribosylates the carboxyl group of Ub Gly76. Because Gly76 is normally used for Ub conjugation to substrates, ADP-ribosylation of the Ub carboxyl terminus precludes ubiquitylation. Parp9 ADP-ribosylation activity therefore restrains the E3 function of Dtx3L. Mutation of the NAD+ binding site in Parp9 increases the DNA repair activity of the heterodimer. Moreover, poly(ADP-ribose) binding to the Parp9 macrodomains increases E3 activity. Dtx3L heterodimerization with Parp9 enables NAD+ and poly(ADP-ribose) regulation of E3 activity.

MeSH terms

  • Adenosine Diphosphate Ribose / metabolism*
  • Cell Line, Tumor
  • DNA Repair
  • HEK293 Cells
  • Humans
  • Mutation
  • NAD / metabolism
  • Neoplasm Proteins / genetics
  • Neoplasm Proteins / metabolism*
  • Neoplasms / enzymology*
  • Neoplasms / genetics
  • Neoplasms / pathology
  • Poly(ADP-ribose) Polymerases / genetics
  • Poly(ADP-ribose) Polymerases / metabolism*
  • Protein Binding
  • Protein Interaction Domains and Motifs
  • RNA Interference
  • Time Factors
  • Transfection
  • Ubiquitin / metabolism*
  • Ubiquitin-Protein Ligases / genetics
  • Ubiquitin-Protein Ligases / metabolism*
  • Ubiquitination

Substances

  • Neoplasm Proteins
  • PARP9 protein, human
  • Ubiquitin
  • NAD
  • Adenosine Diphosphate Ribose
  • DTX3L protein, human
  • Ubiquitin-Protein Ligases
  • Poly(ADP-ribose) Polymerases