Hepatitis C Virus NS5A Protein Modulates Transcription through a Novel Cellular Transcription Factor SRCAP*
- Asish K. Ghosh‡,
- Mainak Majumder‡,
- Robert Steele‡,
- Peter Yaciuk§,
- John Chrivia¶,
- Ranjit Ray‖ and
- Ratna B. Ray‡‖**
- From the Departments of ‡Pathology,§Molecular Microbiology and Immunology, and¶Pharmacological and Physiological Sciences, and the‖Division of Infectious Diseases and Immunology, Saint Louis University, St. Louis, Missouri 63104
Abstract
Hepatitis C virus NS5A protein transcriptionally modulates cellular genes and promotes cell growth. NS5A is likely to exert its activity in concert with cellular factor(s). Using a yeast two-hybrid screen, we have demonstrated that NS5A interacts with the C-terminal end of a newly identified cellular transcription factor, SRCAP. The authenticity of this interaction was verified by a mammalian two-hybrid assay, in vitro pull-down experiment, and anin vivo coimmunoprecipitation assay in human hepatoma (HepG2) cells. An in vitro transient transfection assay demonstrated that SRCAP can efficiently activate transcription when recruited by the Gal4 DNA-binding domain to the promoter. However, down-regulation of p21 promoter activity by NS5A was enhanced following ectopic expression of SRCAP. Together these results suggest that the interaction of NS5A and SRCAP may be one of the mechanisms by which NS5A exerts its effect on cell growth regulation contributing to hepatitis C virus-mediated pathogenesis.
Footnotes
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↵* This research was supported by Public Health Service Grants AI45144 (to R. B. R.) and DK56143 (to R. R.) from the National Institutes of Health.The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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↵** To whom correspondence should be addressed: Dept. of Pathology, Saint Louis University, 1402 S. Grand Blvd., 4th Fl., St. Louis, MO 63104. Tel.: 314-577-8331; Fax: 314-771-3816; E-mail: rayrb@slu.edu.
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↵2 A. K. Ghosh and R. B. Ray, unpublished observation.
- Abbreviations:
- HCV
-
hepatitis C virus
- CAT
-
chloramphenicol acetyl transferase
- PAGE
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polyacrylamide gel electrophoresis
- GAPDH
-
glyceraldehyde phosphodehydrogenase
- RT-PCR
-
reverse transcription-polymerase chain reaction
- CDK
-
cyclin-dependent kinase
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- Received November 23, 1999.
- The American Society for Biochemistry and Molecular Biology, Inc.
