Trapping PARP-DNA complexes – anti-cancer drug screening

PARPs (Poly ADP ribose polymerases) are found in the nucleus of the cell and they are involved in SSB repair (single-strand DNA breaks). PARP is known to bind damaged DNA through its N-terminal zinc finger domain. Subsequently it starts to synthesize a poly (ADP-ribose) chain which serves as a signal for other DNA-repairing enzymes.

SYNTHETIC_ LEATHALITY

Fig. 1: Principle of synthetic lethality

PARP inhibitors are considered to be promising  candidates as anti cancer drugs (recently Olaparib, the first drug directed against PARP1, has been approved by the European commission). One of the reasons is that some tumors are more dependent on PARP than regular cells. These cancer cells are mutated in BRCA1 or BRCA2 – both genes which are involved in key DNA damage repair mechanisms. In healthy cells PARPs can function as a kind of back-up system and let the cells survive even without functional BRCA gene products. When PARPs are inhibited the cells do not possess any functional SSB repair mechanism anymore and are bound to die (Fig. 1; take a look at PARPs as cancer drug targets – first EC-approved drug to learn more about the concept of “synthetic lethality”). [Read more…]

PARP inhibitors involved in Cancer and Parkinson research

In a recent post (PARPs as cancer drug targets – first EC-approved drug) I wrote about Olaparib, a drug against ovarian cancer, which has been developed by AstraZeneca and was approved in December 2014 by the European commission – thus being the first drug directed against a member of the PARP family (Poly ADP-Ribose Polymerases). Furthermore I informed about the tools tebu-bio is able to provide to screen for PARP inhibitors, such as active PARP enzymes and ready-to-use inhibitor screening assays for PARP1 , 2, 3, 6, 7, 10, 11, 14, and 15 as well as for Tankyrase 1 and 2.

In this post, let’s take a look at PARP modulators/reference inhibitors especially linked to cancer and Parkinson’s disease research and screening activities. [Read more…]

PARPs as cancer drug targets – first EC-approved drug

In December 2014, the European commission approved the first drug directed against a member of the PARP familiy (Poly ADP-Ribose Polymerases). Olaparib, a drug against ovarian cancer, has been developed by AstraZeneca and might become an important medicine very soon. Olaparib blocks PARP1 (see the Figure below showing the inhibitory effect of Olaparib on PARP1 measured with the PARP1 Chemiluminescent Activity Assay), an enzyme involved in cell repair, and is designed for ovarian cancer patients with certain hereditary gene mutations. It also has promise in treating other cancers, including breast and gastric tumors, opening up a substantial market opportunity. Olaparib is able to stop cancer cell growth in patients carrying inherited faults in the BRCA1 or BRCA2 genes (BReast CAncer 1 and 2 genes). [Read more…]

Where can I find the best PARPs?

Poly (ADP-ribose) polymerase (PARP) is a family of proteins which catalyze the NAD-dependent addition of Poly ADP-ribose (PAR) chains to nuclear proteins. PARPs play key signaling roles in apoptosis, DNA excision and repair, telomere stability, and chromatin structure. PARPs are also involved in transcriptional regulation of several signaling pathways, including genes involved in cancer and inflammation.

PARPs are composed of four domains of interest: a DNA-binding domain which contains two zinc finger motifs, a caspase-cleaved domain, an auto-modification domain, and a catalytic domain.  Upon DNA damage, the DNA-binding domain binds the damaged DNA and induce a conformational shift, subsequently the catalytic domain starts with the synthesis of a poly (ADP-ribose) chain (PAR) as a signal for the other DNA-repairing enzymes e.g. DNA ligase III. Finally the auto-modification domain is responsible for releasing the protein from the DNA after catalysis and plays an integral role in cleavage-induced inactivation.

PARP1 activity measured using the PARP1 Chemiluminescent Activity Assay Kit, (Cat. 14980569). Luminescence was measured using a Bio-Tek microplate reader. IC50 determination of the PARP inhibitor AZD2281.

PARP1 activity measured using the PARP1 Chemiluminescent Activity Assay Kit, (Cat. 14980569). Luminescence was measured using a Bio-Tek microplate reader. IC50 determination of the PARP inhibitor AZD2281.

Broadest portfolio of PARPs and PARP related products

If you’re studying enzyme kinetics or screening small molecular inhibitors for drug discovery and HTS applications, you’ll need to access PARP isozymes. BPS Biosciences provides 13 different PARP isozymes (out of 17 isozymes known). They also have a selection of 18 different kits for your activity and inhibitor screening assays, as well as a large number of PARP inhibitors and substrates.  All these products have shown to be reliable and trouble-free.

Are you working on PARP related screening projects? Share any comments or ask your questions below!

PARP and Top1 inhibitors most beneficial in endonuclease-deficient cancer cells

The synergistic combination of Poly(ADP-ribose) polymerases (PARP) and Topoisomerase I (Top1) inhibitors most beneficial on endonuclease-deficient cancer cells in cancer therapies ?

This is one of the elements discussed in the recent publication by Dr Benu Brata (National Institutes of Health (USA) and Indian Association for the Cultivation of Science (India) in Nucleic Acids Research. (1)

[Read more…]