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J. Virol., Nov 1995, 7169-7179, Vol 69, No. 11
SJ Plotch and O Palant
Poliovirus protein 3B (also known as VPg) is covalently linked to the 5'
ends of both genomic and antigenomic viral RNA. Genetic and biochemical
studies have implicated protein 3AB, the membrane-bound precursor to VPg,
in the initiation of genomic RNA synthesis. We have purified 3AB to near
homogeneity following thrombin cleavage of purified glutathione
S-transferase-3AB. When added to transcription reaction mixtures catalyzed
by poliovirus RNA polymerase (3Dpol), 3AB stimulated RNA synthesis up to
75-fold with oligo(U)-primed virion RNA, globin mRNA, and unprimed
synthetic, full-length minus-strand viral RNA as the templates. Synthetic
VPg also stimulated RNA synthesis but was only 1 to 2% as effective as 3AB
on a molar basis. The increased level of transcription was not the result
of enhancing the elongation rate of the polymerase. No evidence was found
for uridylylation of 3AB or for covalent linkage to RNA transcription
products. 3AB sedimented as a multimer in glycerol gradients. In the
presence of the polymerase, the sedimentation rate of both proteins
increased, suggesting the formation of a complex. Detergent prevented both
multimerization and complex formation. The polymerase also bound to
immobilized glutathione S- transferase-3AB; this procedure was used to
purify the polymerase to near homogeneity. These results suggest a
mechanism for bringing together 3AB, 3Dpol (or its precursor 3CD), and
viral RNA in host cell membranous vesicles in which all viral RNA synthesis
occurs.
Copyright © 1995, American Society for Microbiology
Poliovirus protein 3AB forms a complex with and stimulates the activity of the viral RNA polymerase, 3Dpol [published erratum appears in J Virol 1996 Jan;70(1):682]
Molecular Biology Research Section, Lederle Laboratories, American Cyanamid Company, Pearl River, New York 10965, USA.
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