VP1 of infectious bursal disease virus is an RNA-dependent RNA polymerase.
Segment B of the bisegmented, double-stranded RNA genome of infectious bursal disease virus (IBDV) encodes the viral protein VP1. This has been presumed to represent the RNA-dependent RNA polymerase (RdRp) as it contains motifs that are typical for the RdRp of plus-strand RNA viruses. Here it is demonstrated that baculovirus-expressed wild-type but not motif A mutated VP1 acts as an RdRp on IBDV-specific RNA templates. Thus, on a plus-strand IBDV segment A cRNA template, minus-strand synthesis occurred in such a way that a covalently linked double-stranded RNA product was generated (by a 'copy-back' mechanism). Importantly, enzyme activity was observed only with templates that comprised the 3' non-coding region of plus-strand RNAs transcribed from IBDV segments A and B, indicating template specificity. RdRp activity was shown to have a temperature optimum of 37 degrees C and required magnesium ions for enzyme activity. Thus, it has been demonstrated unequivocally that VP1 represents the RdRp of IBDV.
von Einem
Ursula I
UI
Institute of Molecular Biology, Federal Research Centre for Viral Diseases of Animals, Boddenblick 5a, 17493 Greifswald-Insel Riems, Germany.
Gorbalenya
Alexander E
AE
Department of Medical Microbiology, Center of Infectious Diseases, Leiden University Medical Center, Postbus 9600, 2300 RC Leiden, The Netherlands.
Schirrmeier
Horst
H
Institute for Diagnostic Virology, Federal Research Centre for Viral Diseases of Animals, Boddenblick 5a, 17493 Greifswald-Insel Riems, Germany.
Behrens
Sven-Erik
SE
Fox Chase Cancer Center, 7701 Burholme Avenue, Philadelphia, PA 19111, USA.
Letzel
Tobias
T
Institute of Molecular Biology, Federal Research Centre for Viral Diseases of Animals, Boddenblick 5a, 17493 Greifswald-Insel Riems, Germany.
Mundt
Egbert
E
Institute of Molecular Biology, Federal Research Centre for Viral Diseases of Animals, Boddenblick 5a, 17493 Greifswald-Insel Riems, Germany.
D000818:Animals; D002384:Catalysis; D012367:RNA, Viral / Q000096:biosynthesis; D012324:RNA-Dependent RNA Polymerase / Q000378:metabolism*; D018411:Spodoptera; D015678:Viral Structural Proteins / Q000378:metabolism*
D012367:RNA, Viral; C107669:VP1 protein, infectious bursal disease virus; D015678:Viral Structural Proteins; D012324:RNA-Dependent RNA Polymerase