Regulation of (+):(-)-strand asymmetry in replication of brome mosaic virus RNA.
Transfection of barley protoplasts with brome mosaic virus (BMV) RNAs 1 + 2 in the absence of RNA-3 yielded a molar ratio for (+):(-)-strand progeny at 24 hr postinoculation near unity, whereas over 100-fold more (+)- than (-)-strand progeny accumulated in its presence. The presence of RNA-3 enhanced total (+)-strand RNA production 205-fold and that of RNAs 1 + 2 by 29-fold. In contrast, total (-)-strand RNA accumulation decreased by 68% and that for (-)RNAs 1 + 2 by 79% in the presence of RNA-3. Transfections containing an RNA-3 mutant (Gsgi----U RNA-3) that is incapable of yielding RNA-4 as a result of a single nucleotide substitution at the subgenomic RNA initiation site yielded only 66% of the (+):(-) asymmetry seen in the presence of wild-type RNA-3. Only 1.8-fold excess of (+)-over (-)-strand production was obtained for transfections that included delta SGP RNA-3, a deletion that includes the subgenomic promoter core and extends 43 nt into the RNA-4 sequence. Transfections containing RNA-3 mutants bearing frameshifts or deletions in the coat protein cistron yielded levels of asymmetry similar to those seen for Gsgi----U RNA-3. These findings implicate the subgenomic promoter and other sequences in the intercistronic region of RNA-3 as the primary determinants of asymmetric replication, although the coat protein may be an additional factor enhancing the accumulation of (+)-strand RNA.
Marsh
L E
LE
Department of Biology, Texas A&M University, College Station 77843-3258.
Huntley
C C
CC
Pogue
G P
GP
Connell
J P
JP
Hall
T C
TC
D002213:Capsid / Q000235:genetics; D003001:Cloning, Molecular; D004252:DNA Mutational Analysis; D001467:Hordeum / Q000382:microbiology; D009029:Mosaic Viruses / Q000235:genetics*; D010957:Plasmids; D011401:Promoter Regions, Genetic; D012367:RNA, Viral / Q000235:genetics*; D015183:Restriction Mapping; D014158:Transcription, Genetic; D014779:Virus Replication
D012367:RNA, Viral