Molecular Biology Resources

6143 North 60th Street
Milwaukee, WI, USA 53218-1606

Phone 800.626.7873

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Did you know that 75% of toxicity-related problems are not detected until preclinical or later stages of drug testing?

MBR offers assay services to investigate the effects of drug compounds on key DNA replication and repair enzymes, such as human DNA polymerase α (alpha), human DNA polymerase β (beta), human DNA polymerase γ (gamma), and HeLa cell extracts (containing replication protein complexes).

Our assays are designed to quantify the extent of inhibition and the range of concentrations of the drug, where it elicits inhibitory response. The assay includes optimization of the kinetic of each enzyme used in the study; assay of the inhibitory effects of test compound over a broad dilution range, and determination of IC50 values. These assays are designed to save pharmaceutical companies time and money due to the possible elimination of toxic compounds in earlier phases of the drug-testing process. 

MBR's Two-Phase Testing Process

The service consists of two phases. The first phase challenges the drug compound over a broad range (15,000 fold), and is used as an indicator to determine whether the degree of inhibition justifies further investigation or disqualifies the drug candidate from further consideration. The second phase is to quantify the extent of inhibition (IC50), specifically attributable to the drug compound.

Phase I

In phase I, three DNA-dependent human DNA polymerases, alpha, beta, and gamma, will each be tested in duplicate assays over six concentrations. The client will determine the starting concentration of the drug compound. Each assay will be repeated, at least once. In addition, the assay will be conducted for both negative and positive controls. Thus, a total of 32 reactions will be conducted to measure drug response. This range of reactions will be conducted for each of three DNA-dependent human polymerases.

Phase II

In phase II, based on the results from the phase I, a narrow range of drug concentration will be tested to quantify the IC50 values, a dose at which the drugs exhibits 50% of its maximal activity. These values will aid in determining a safe threshold dose of the drug for administration in humans. MBR will consult with your organization on the details of the service and further fine tune the assay system to meet your needs.

What makes MBR's compund testing so unique?

Costly and time consuming cell culture or animal feeding studies to test toxicity of drugs can be minimized and/or avoided by using our in vitro assay systems. MBR's genotoxicity tests are designed to directly test the effect of drugs on relevant human proteins and enzymes involved in vital DNA replication and repair processes to ultimately assess the deleterious effect on vital human cell and organ functions.

Human DNA polymerase alpha (H-pol alpha) is a cell DNA-dependent DNA polymerase necessary for initiation of the process of DNA replication in all cells. The human DNA polymerase beta (H-pol beta) is required in DNA repair mechanisms for correcting the mutations caused by chemicals. Hence, the testing of drugs on H-pol Beta gives insight into the dose levels that harm the vital function of DNA repair. Similarly, the human DNA polymerase gamma (H-pol gamma) is the only known DNA polymerase in human mitochondria that is essential for mitochondrial DNA replication and repair. It is well established that defects in mitochondrial DNA replication lead to its dysfunction characterized by DNA deletions. These lead to diseases, such as, progressive external ophthalmoplegia (PEO), Alpers syndrome and other infantile hepato-cerebral syndromes, ataxia–neuropathy syndromes, Charcot–Marie–Tooth disease, idiopathic parkinsonism, nucleoside reverse-transcriptase inhibitor (NRTI) toxicity, etc. Mitochondria are involved in critical oxidative functions and are present in abundance the lungs, liver and heart tissues.  Mitochondrial toxicity of drugs in these organs have serious impact on the vital respiratory functions. 

To learn more, or to get in touch with our investigators about using our unique service, please send us an email at or call us at 800-626-7873.