Poly (ADP-ribose) polymerase (PARP) is a family of proteins that, generally speaking, transfer ADP-ribose units from NAD+ onto target nuclear proteins, forming long branched Poly ADP-ribose (PAR) chains. PARPs play key signaling roles in apoptosis, DNA excision and repair, and chromatin structure. PARPs are also involved in transcriptional regulation of several signaling pathways, including genes involved in inflammation.
Some of the PARP proteins are known as tankyrases (PARP5A and 5B). In particular, tankyrases (TNKS) play a role in the maintenance of telomere length, sister telomere association, and mitotic spindle organization. Tankyrase 1 also destabilizes axin, thereby activating Wnt signaling and driving tumor cell proliferation. Thus, the PARPs, and particularly the TNKS have become important cancer drug targets. Further evidence for this comes from the fact that PARP is overexpressed in lung, ovarian, and breast cancer, and PARP inhibitors are showing dramatic therapeutic potential for breast and ovarian cancer in phase I and II clinical trials.
In addition to the role of TNKS in cancer, PARPs participate in a number of other normal and disease-associated biological processes. PARP1 binds DNMT1 and indirectly regulates DNA methylation. PARP also remodels chromatin by PARylating histones and relaxing chromatin structure. PARP2 is a substrate for histone acetyltransferases PCAF and GCN5L. PARP7 plays a role in adaptive responses to chemical exposure and mediates certain effects of the chemicals. Mice deficient in the PARP DNA repair enzyme are refractory to toxin-induced death of pancreatic beta cells and do not become diabetic. Finally, cleavage of PARP1 by caspases 3 and 7 is considered one of the classic markers of apoptosis. PARP directly induces caspase-independent apoptosis, via the production of PAR, which stimulates mitochondria to release AIF.
BPS is the only company to offer an extensive portfolio of PARP isozymes. Additionally, we offer assay kits, inhibitors, and recombinant histone substrates. Screening and profiling services are also available for over 10 different PARPs.
1. Ame, J.C., et al., BioEssays.2004; 26(8): 882-893.
2. Rouleau, M., et al., Nat. Rev. Canc. 2010; 10: 293-301.