Hc. Guan et al., Requirement of a 5 '-proximal linear sequence on minus strands for plus-strand synthesis of a satellite RNA associated with turnip crinkle virus, VIROLOGY, 268(2), 2000, pp. 355-363
Viral RNA replication begins with specific recognition of cis-acting RNA el
ements by the viral RNA-dependent RNA polymerase (RdRp) and/or associated h
ost factors. A short RNA element (3'-AACCCCUGGGAGGC) located 41 bases from
the 5' end of minus strands of satellite RNA C (satC), a 356-base subviral
RNA naturally associated with turnip crinkle virus (TCV), was previously id
entified as important for plus-strand synthesis using an in vitro RdRp assa
y (H. Guan, C. Song, A. E. Simon, 1997, RNA 3, 1401-1412). To examine the f
unctional significance of this element in RNA replication, mutations were i
ntroduced into the consecutive C residues in the element. A single mutation
of the 3'-most C residue resulted in undetectable levels of satC plus stra
nds when transcripts were assayed in protoplasts and suppressed transcripti
on directed by the element in vitro. However, satC minus strands were detec
table at 6 h postinoculation (hpi) of protoplasts, accumulating to about 10
% of wild-type levels at 24 hpi. This mutation, when in the plus-sense orie
ntation, had little or no effect on minus-strand synthesis from full-length
satC plus strands in vitro, suggesting that the 5'-proximal RNA element is
required for satC plus-strand synthesis. in addition, in vivo genetic sele
ction revealed a strict requirement for 10 of the 14 nucleotides of the ele
ment, indicating that the primary sequence is essential for RNA accumulatio
n, (C) 2000 Academic Press.