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J. Virol., 10 1996, 6658-6664, Vol 70, No. 10
CK Ho, JL Van Etten and S Shuman
We report that the A103R protein of Chlorella virus PBCV-1 is an mRNA
capping enzyme that catalyzes the transfer of GMP from GTP to the 5'
diphosphate end of RNA. This is a two-step reaction in which the enzyme
first condenses with GTP to form a covalent enzyme-GMP intermediate and
then transfers the GMP to an RNA acceptor to form a GpppN cap. Purified
recombinant Al03R is a 38-kDa monomer that lacks RNA (guanine-7-)
methyltransferase activity. With respect to its size, amino acid sequence,
and biochemical properties, A103R is more closely related to the yeast RNA
guanylyltransferases than it is to the multifunctional capping enzymes
coded for by other large DNA viruses--the poxviruses and African swine
fever virus. We surmise that in order to cap its transcripts, PBCV-l must
either encode additional 5' processing activities or else rely on the host
alga to provide these functions.
Copyright © 1996, American Society for Microbiology
Expression and characterization of an RNA capping enzyme encoded by Chlorella virus PBCV-1
Molecular Biology Program, Sloan-Kettering Institute, New York, New York 10021, USA.
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