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  • The EMBO Journal (2002) 21, 1168 - 1176
  • doi:10.1093/emboj/21.5.1168

The hepatitis C viral NS3 protein is a processive DNA helicase with cofactor enhanced RNA unwinding

Phillip S. Pang1,2, Eckhard Jankowsky3, Paul J. Planet2,4 and Anna Marie Pyle1,5

  1. Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA
  2. Medical Scientist Training Program, Columbia College of Physicians and Surgeons, New York, NY, USA
  3. Department of Biochemistry, School of Medicine, Case Western Reserve University, Cleveland, OH, USA
  4. Integrated Program in Cellular, Molecular and Biophysical Sciences, Columbia University New York, NY, USA
  5. Howard Hughes Medical Institute, Columbia University, New York, NY, USA

Correspondence to:

Anna Marie Pyle, E-mail: amp11@columbia.edu

Received 2 August 2001; Accepted 9 January 2002; Revised 3 December 2001

The RNA helicase/protease NS3 plays a central role in the RNA replication of hepatitis C virus (HCV), a cytoplasmic RNA virus that represents a major worldwide health problem. NS3 is, therefore, an important drug target in the effort to combat HCV. Most work has focused on the protease, rather than the helicase, activities of the enzyme. In order to further characterize NS3 helicase activity, we evaluated individual stages of duplex unwinding by NS3 alone and in complex with cofactor NS4A. Despite a putative replicative role in RNA unwinding, we found that NS3 alone is a surprisingly poor helicase on RNA, but that RNA activity is promoted by cofactor NS4A. In contrast, NS3 alone is a highly processive helicase on DNA. Phylogenetic analysis suggests that this robust DNA helicase activity is not vestigial and may have specifically evolved in HCV. Given that HCV has no replicative DNA intermediate, these findings suggest that NS3 may have the capacity to affect host DNA.

  • Keywords:

    • DExH,
    • D,
    • helicase,
    • hepatitis C,
    • NS3,
    • NS4A