R. Di et al., TRANSLATIONAL FRAMESHIFTING BY BARLEY YELLOW DWARF VIRUS-RNA (PAV SEROTYPE) IN ESCHERICHIA-COLI AND IN EUKARYOTIC CELL-FREE-EXTRACTS, Molecular plant-microbe interactions, 6(4), 1993, pp. 444-452
The open reading frame (39K ORF) at the 5' end of the genome of barley
yellow dwarf virus, PAV serotype (BYDV-PAV), overlaps with a 60K ORF
by 13 nucleotides. Several approaches were used to show that the 60K O
RF (putative polymerase gene) is translated by a low-frequency framesh
ift event in which some ribosomes shift into the 60K ORF rather than t
erminate at the 39K ORF stop codon. A sequence encompassing this regio
n of overlap induced minus one (-1) translational frameshifting in het
erologous and native contexts. In Escherichia coli, with the a subunit
of lacZ used as a reporter gene, the rate of frameshifting caused by
the BYDV-PAV sequence was approximately 3%. Amino acid sequencing of t
he transframe protein confirmed that ribosomes slip into the -1 frame
in the overlapping region which includes a consensus shifty heptanucle
otide: GGGUUUU. In a wheat germ translation system, BYDV-PAV genomic R
NA from virions frameshifted about twice as efficiently as full-length
transcripts from a cDNA clone. Frameshifting in rabbit reticulocyte l
ysates was much lower for either template. The identity of the 99-kDa
wheat germ translation product was verified as the transframe protein
by immunoprecipitation with antibody specific for the 60K ORF. These r
esults support our previous observations of frameshifting in protoplas
ts and illustrate a subtle molecular control mechanism between this pa
thogen and its host cells.