Il-Ryong Choi and K. Andrew White 1
From the Department of Biology, York University, Toronto, Ontario M3J 1P3, Canada
1 To whom correspondence should be addressed: Dept. of
Biology, York University, 4700 Keele St., Toronto,
Ontario M3J 1P3, Canada.
Tel.: 416-736-5243; Fax: 416-736-5698;
E-mail: kawhite@yorku.ca
Many (+)-strand RNA viruses transcribe small subgenomic (sg) mRNAs
that allow for regulated expression of a subset of their genes. Tomato
bushy stunt virus (TBSV) transcribes two such messages and here we report
the identification of a long-distance RNA·RNA interaction that is
essential for the efficient accumulation
of capsid protein-encoding sg mRNA1. The relevant base pairing interaction
occurs within the TBSV RNA
genome between a 7-nucleotide (nt) long sequence, separated by just
3 nt from the downstream sg mRNA1 initiation site, and a complementary
sequence positioned some ~1000 nt further upstream. Analyses of this interaction
indicate that it (i) functions in the (+)-strand, (ii) modulates both (+)-
and (-)-strand sg mRNA1 accumulation, (iii) specifically regulates the
accumulation of sg mRNA1 (-)-strands, (iv) controls sg mRNA1 expression
from an ectopic transcriptional initiation site, (v) may occur in cis
and, and (vi) could nucleate the formation of a more complex RNA structure.
These data are most consistent with a role for this interaction in regulating
sg mRNA1 accumulation at the level of transcription.
* This research was supported by grants from
the Natural Sciences and Engineering Research Council of
Canada and a Premier's Research Excellence Award (to K. A. W.).The
costs of publication of this article were defrayed in part by the payment
of page charges. The article must therefore be hereby marked "advertisement"
in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
1. Frenster JH, "Nuclear Polyanions as De-Repressors of Synthesis of Ribonucleic Acid", Nature, vol. 206, no. 4985, pp. 680-683 (May 15, 1965).
2. Frenster JH, "Activation of DNA Transcription within Repressed
Chromatin by Nuclear RNA Species",
RNA 2001, p.
237 (RNA Society, Bethesda, MD).