The Hepatitis E Virus Open Reading Frame 3 Protein Activates ERK through Binding and Inhibition of the MAPK Phosphatase*
- Anindita Kar-Roy‡,
- Hasan Korkaya‡§,
- Ruchi Oberoi,
- Sunil Kumar Lal and
- Shahid Jameel, A Wellcome Trust International Senior Research Fellow in Biomedical Sciences¶
- Virology Group, International Centre for Genetic Engineering and Biotechnology, New Delhi 110067, India
- ↵¶ To whom correspondence should be addressed: Virology Group, ICGEB, Aruna Asaf Ali Marg, New Delhi 110067, India. Tel.: 91-11-26176680; Fax: 91-11-26162316; E-mail: shahid{at}icgeb.res.in.
Abstract
The hepatitis E virus causes acute viral hepatitis endemic in much of the developing world and is a serious public health problem. However, due to the lack of an in vitro culture system or a small animal model, its biology and pathogenesis are poorly understood. We have shown earlier that the ORF3 protein (pORF3) of hepatitis E virus activates ERK, a member of the MAPK superfamily. Here we have explored the mechanism of pORF3-mediated ERK activation and demonstrated it to be independent of the Raf/MEK pathway. Using biochemical assays, yeast two-hybrid analysis, and intracellular fluorescence resonance energy transfer we showed that pORF3 binds Pyst1, a prototypic member of the ERK-specific MAPK phosphatase. The binding regions in the two proteins were mapped to the N terminus of pORF3 and a central portion of Pyst1. Expression of pORF3 protected ERK from the inhibitory effects of ectopically expressed Pyst1. This is the first example of a viral protein regulating ERK activation by inhibition of its cognate dual specificity phosphatase.
- Received January 15, 2004.
- Revision received April 13, 2004.
- The American Society for Biochemistry and Molecular Biology, Inc.
