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J. Virol., 11 1995, 6742-6750, Vol 69, No. 11
P Liston and DJ Briedis
Members of the Paramyxoviridae family utilize a variety of different
strategies to increase coding capacity within their P cistrons. Translation
initiation at alternative 5'-proximal AUG codons is used by measles virus
(MV) to express the virus-specific P and C proteins from overlapping
reading frames on their mRNAs. Additional species of mRNAs are transcribed
from the MV P cistron by the insertion of extra nontemplated G residues at
a specific site within the P transcript. Addition of only a single
nontemplated G residue results in the expression of the V protein, which
contains a unique carboxyl terminus. We have used an Escherichia coli
system to express MV P cistron-related mRNAs and proteins. We have found
that ribosomal frameshifting on the MV P protein mRNA is capable of
generating a previously unrecognized P cistron-encoded protein that we have
designated R. Some ribosomes which have initiated translation of the P
protein mRNA use the sequence TCC CCG AG (24 nucleotides upstream of the V
protein stop codon) to slip into the -1 reading frame, thus translating the
sequence as TC CCC GAG. The resulting R protein terminates five codons
downstream of the frameshift site at the V protein stop codon. We have gone
on to use a chloramphenicol acetyltransferase reporter system to
demonstrate that this MV-specific sequence is capable of directing
frameshifting during in vivo translation in eukaryotic cells. Analysis of
immunoprecipitated proteins from MV-infected cells by two-dimensional gel
electrophoresis allowed detection of a protein species consistent with R
protein in MV- infected cells. Quantitation of this protein species allowed
a rough estimation of frameshift frequency of approximately 1.8%.
Significant stimulation of ribosomal frameshift frequency at this locus of
the MV P mRNA was mediated by a downstream stimulator element which,
although not yet fully defined, appeared to be neither a conventional
stem-loop nor an RNA pseudoknot structure.
Copyright © 1995, American Society for Microbiology
Ribosomal frameshifting during translation of measles virus P protein mRNA is capable of directing synthesis of a unique protein
Department of Microbiology and Immunology, McGill University, Montreal, Quebec, Canada.
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