Journal Article

Downregulation of DNA excision repair by the hepatitis B virus-x protein occurs in p53-proficient and p53-deficient cells

Iris Jaitovich Groisman, Rajen Koshy, Frank Henkler, John D. Groopman and Moulay A. Alaoui-Jamali

in Carcinogenesis

Volume 20, issue 3, pages 479-483
Published in print March 1999 | ISSN: 0143-3334
Published online March 1999 | e-ISSN: 1460-2180 | DOI: http://dx.doi.org/10.1093/carcin/20.3.479
Downregulation of DNA excision repair by the hepatitis B virus-x protein occurs in p53-proficient and p53-deficient cells

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Synergism between exposure to chemical carcinogens and infection with the hepatitis B virus (HBV) has been implicated in the high incidence of hepatocellular carcinoma. In this study we report that the HBV protein HBx, inhibits cellular DNA repair capacity in a p53-independent manner. Two alternative assays were used: the host cell reactivation assay, which measures the cell's capacity to repair DNA damage in a reporter plasmid, and unscheduled DNA synthesis, which measures the overall DNA repair capacity in damaged cells. Two p53-proficient cell lines, the hepatocellular carcinoma cell line HepG2 and liver epithelial cell line CCL13, were co-transfected with the pCMV–HBx reporter plasmid and the pCMV–CAT plasmid damaged with UVC radiation. Compared with cells transfected with control plasmid, the presence of HBx resulted in ~50% inhibition of the cell's capacity to reactivate CAT activity of UVC-damaged plasmid, and ~25% inhibition of unscheduled DNA synthesis in cells treated with either aflatoxin B1 epoxide or UVC radiation. Using the p53-deficient cell line Saos-2, we demonstrated that expression of HBx also resulted in diminished overall cellular DNA repair of damage induced by both aflatoxin B1 epoxide and UVC radiation, using both the host cell reactivation and unscheduled DNA synthesis assays. In summary, this study provides evidence for p53-independent regulation of DNA repair by HBx.

Keywords: CAT, chloramphenicol acetyl transferase; CMV, cytomegalovirus; HBV, hepatitis B virus; HBx, hepatitis B virus-x protein; HCC, hepatocellular carcinoma; HCR, host cell reactivation; NER, nucleotide excision repair; UDS, unscheduled DNA synthesis.

Journal Article.  4639 words.  Illustrated.

Subjects: Clinical Cytogenetics and Molecular Genetics

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