Sensitivity of Mitochondrial Transcription and Resistance of RNA Polymerase II Dependent Nuclear Transcription to Antiviral Ribonucleosides

• Published in: PLoS pathogens Vol. 8; no. 11; p. e1003030
• Main Authors: Arnold, Jamie J., Sharma, Suresh D., Feng, Joy Y., Ray, Adrian S., Smidansky, Eric D., Kireeva, Maria L., Cho, Aesop, Perry, Jason, Vela, Jennifer E., Park, Yeojin, Xu, Yili, Tian, Yang, Babusis, Darius, Barauskus, Ona, Peterson, Blake R., Gnatt, Averell, Kashlev, Mikhail, Zhong, Weidong, Cameron, Craig E.
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 01.11.2012; Public Library of Science (PLoS)
• Subjects: Animals; Antiviral agents; Antiviral Agents - adverse effects; Antiviral Agents - pharmacology; Biology; Cancer; Cattle; Cell Line; Cell Nucleus - metabolism; DNA-Directed RNA Polymerases - metabolism; Dosage and administration; Drug therapy; Genetic aspects; Genetic transcription; Health aspects; Hepacivirus - metabolism; Hepatitis C; Hepatitis C - drug therapy; Hepatitis C - enzymology; Medicine; Metabolites; Mitochondria; Mitochondria - metabolism; Mitochondrial DNA; Physiological aspects; Ribonucleosides - adverse effects; Ribonucleosides - pharmacology; RNA polymerase; RNA Polymerase II - metabolism; RNA polymerases; RNA, Viral - biosynthesis; Studies; Toxicity; Transcription, Genetic - drug effects; Viral genetics; United States
• ISSN: 1553-7374; 1553-7366; 1553-7374
• DOI: 10.1371/journal.ppat.1003030

Ribonucleoside analogues have potential utility as anti-viral, -parasitic, -bacterial and -cancer agents. However, their clinical applications have been limited by off target effects. Development of antiviral ribonucleosides for treatment of hepatitis C virus (HCV) infection has been hampered by appearance of toxicity during clinical trials that evaded detection during preclinical studies. It is well established that the human mitochondrial DNA polymerase is an off target for deoxyribonucleoside reverse transcriptase inhibitors. Here we test the hypothesis that triphosphorylated metabolites of therapeutic ribonucleoside analogues are substrates for cellular RNA polymerases. We have used ribonucleoside analogues with activity against HCV as model compounds for therapeutic ribonucleosides. We have included ribonucleoside analogues containing 2'-C-methyl, 4'-methyl and 4'-azido substituents that are non-obligate chain terminators of the HCV RNA polymerase. We show that all of the anti-HCV ribonucleoside analogues are substrates for human mitochondrial RNA polymerase (POLRMT) and eukaryotic core RNA polymerase II (Pol II) in vitro. Unexpectedly, analogues containing 2'-C-methyl, 4'-methyl and 4'-azido substituents were inhibitors of POLRMT and Pol II. Importantly, the proofreading activity of TFIIS was capable of excising these analogues from Pol II transcripts. Evaluation of transcription in cells confirmed sensitivity of POLRMT to antiviral ribonucleosides, while Pol II remained predominantly refractory. We introduce a parameter termed the mitovir (mitochondrial dysfunction caused by antiviral ribonucleoside) score that can be readily obtained during preclinical studies that quantifies the mitochondrial toxicity potential of compounds. We suggest the possibility that patients exhibiting adverse effects during clinical trials may be more susceptible to damage by nucleoside analogs because of defects in mitochondrial or nuclear transcription. The paradigm reported here should facilitate development of ribonucleosides with a lower potential for toxicity.