Journal of Virology, February 2001, p. 1899-1908, Vol. 75, No. 4
0022-538X/01/$04.00+0 DOI: 10.1128/JVI.75.4.1899-1908.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.


Laboratory of Molecular Medical Engineering, Department of Biological Information, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Midori-ku, Yokohama 226-8501,1 and Central Laboratories for Key Technology, Kirin Brewery Company, Kanazawa-ku, Yokohama, Kanagawa 236-0004,3 Japan, and Department of Microbiology, Mount Sinai School of Medicine, New York, New York 10029-65742
Received 2 August 2000/Accepted 16 November 2000
Previous biochemical data identified a host cell fraction, designated RAF-2, which stimulated influenza virus RNA synthesis. A 48-kDa polypeptide (RAF-2p48), a cellular splicing factor belonging to the DEAD-box family of RNA-dependent ATPases previously designated BAT1 (also UAP56), has now been identified as essential for RAF-2 stimulatory activity. Additionally, RAF-2p48 was independently identified as an influenza virus nucleoprotein (NP)-interacting protein, NPI-5, in a yeast two-hybrid screen of a mammalian cDNA library. In vitro, RAF-2p48 interacted with free NP but not with NP bound to RNA, and the RAF-2p48-NP complex was dissociated following addition of free RNA. Furthermore, RAF-2p48 facilitated formation of the NP-RNA complexes that likely serve as templates for the viral RNA polymerase. RAF-2p48 was shown, in both in vitro binding assays and the yeast two-hybrid system, to bind to the amino-terminal region of NP, a domain essential for RNA binding. Together, these observations suggest that RAF-2p48 facilitates NP-RNA interaction, thus leading to enhanced influenza virus RNA synthesis.
Present address: Department of Virology, Center for Basic Research,
The Kitasato Institute, Minato-ku, Tokyo 108-8642, Japan.
Present address: Department of Viral Vaccine Research,
Wyeth-Lederle Vaccines and Pediatrics, Pearl River, NY 10965.
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