Combining Chemical Genetics with Proximity-Dependent Labeling Reveals Cellular Targets of Poly(ADP-ribose) Polymerase 14 (PARP14)

Poly­(ADP-ribose)
polymerase 14 (PARP14) is a member of the PARP
family of enzymes that transfer ADP-ribose from NAD+ to
nucleophilic amino acids on target proteins, a process known as mono-ADP-ribosylation
(MARylation). PARP14 is involved in normal immune function through
the IL-4 signaling pathway and is a prosurvival factor in multiple
myeloma and hepatocellular carcinoma. A mechanistic understanding
of the physiological and pathophysiological roles of PARP14 has been
limited by the dearth of PARP14-specific MARylation targets. Herein
we engineered a PARP14 variant that uses an NAD+ analog
that is orthogonal to wild-type PARPs for identifying PARP14-specific
MARylation targets. Combining this chemical genetics approach with
a BioID approach for proximity-dependent labeling of PARP14 interactors,
we identified 114 PARP14-specific protein substrates, several of which
are RNA regulatory proteins. One of these targets is PARP13, a protein
known to play a role in regulating RNA stability. PARP14 MARylates
PARP13 on several acidic amino acids. This study not only reveals
crosstalk among PARP family members but also highlights the advantage
of using disparate approaches for identifying the direct targets of
individual PARP family members.