Cellular splicing factor RAF-2p48/NPI-5/BAT1/UAP56 interacts with the influenza virus nucleoprotein and enhances viral RNA synthesis.
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.
Momose
F
F
Laboratory of Molecular Medical Engineering, Department of Biological Information, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Midori-ku, Yokohama 226-8501, Japan.
Basler
C F
CF
O'Neill
R E
RE
Iwamatsu
A
A
Palese
P
P
Nagata
K
K
D000251:Adenosine Triphosphatases / Q000302:isolation & purification / Q000378:metabolism*; D015967:Gene Expression Regulation, Viral; D006367:HeLa Cells; D006801:Humans; D009980:Influenza A virus / Q000235:genetics / Q000378:metabolism*; D009687:Nuclear Proteins / Q000302:isolation & purification / Q000378:metabolism*; D009698:Nucleoproteins / Q000378:metabolism*; D020365:RNA Helicases / Q000302:isolation & purification / Q000378:metabolism; D012326:RNA Splicing; D012367:RNA, Viral / Q000096:biosynthesis* / Q000378:metabolism; D017381:Spliceosomes / Q000378:metabolism; D020798:Two-Hybrid System Techniques
D009687:Nuclear Proteins; D009698:Nucleoproteins; D012367:RNA, Viral; D000251:Adenosine Triphosphatases; C027900:RNA-dependent ATPase; D020365:RNA Helicases