What are PARPs and their role in biology?
Poly (ADP-ribose) polymerases (PARPs) are a family of 16 enzymes that regulate fundamental cellular processes including gene expression, protein degradation, and multiple cellular stress responses. PARPs alter the function of target proteins by post-translational modification using nicotinamide adenine dinucleotide (NAD+), an essential small molecule metabolite found in all living cells. Additionally, there are multiple enzymes that remove (“erase”) this modification, as well as several proteins that contain ADP-ribose binding modules (“readers”).
What are the different kinds of PARPs?
PARPs can be classified based upon the type of modification made to target proteins.
- PolyPARPs modify their protein targets with large branched polymers called poly(ADP-ribose) or PAR. This large and highly charged attachment creates a protein recruitment scaffold that directs proteins to function at specific sites within the cell.
- MonoPARPs modify their targets with single units of ADP-ribose called mono(ADP-ribose), or MAR, that modulate signal transduction pathways similarly to kinase phosphorylation.
What is the role of PARPs in cellular pathways?
Due to the large size of the PARP family of proteins and its diverse activity and different target proteins, PARPs are involved in many key cellular pathways and have important roles in DNA repair, transcription, heat shock and cytoplasmic stress response, protein degradation, cell division, RNA processing and more.