Abstract
The genomic RNA of the coronavirus IBV contains an efficient ribosomal frameshift signal at the junction of the overlapping 1a and 1b open reading frames. The signal is comprised of two elements, a heptanucleotide “slip-site” and a downstream tertiary RNA structure in the form of an RNA pseudoknot. We have investigated the structure of the pseudoknot and its contribution to the frameshift process by analysing the frameshifting properties of a series of pseudoknot mutants. Our results show that the pseudoknot structure closely resembles that which can be predicted from current building rules, although base-pair formation at the region where the two pseudoknot stems are thought to stack co-axially is not a pre-requisite for efficient frameshifting. The stems, however, must be in close proximity to generate a functional structure. In general, the removal of a single base-pair contact in either stem is sufficient to reduce or abolish frameshifting. No primary sequence determinants in the stems or loops appear to be involved in the frameshift process; as long as the overall structure is maintained, frameshifting is highly efficient. Thus, small insertions into the pseudoknot loops and a deletion in loop 2 that reduced its length to the predicted functional minimum did not influence frameshifting. However, a large insertion (467 nucleotides) into loop 2 abolished frameshifting. A simple stem-loop structure with a base-paired stem of the same length and nucleotide composition as the stacked stems of the pseudoknot could not functionally replace the pseudoknot, suggesting that some particular conformational feature of the pseudoknot determines its ability to promote frameshifting.
Keywords: RNA pseudoknot, ribosomal frameshifting, coronavirus, translational regulation, RNA structure
Abbreviations: RSV, Rous sarcoma virus; MMTV, mouse mammary tumour virus; IBV, infectious bronchitis virus; ORF, open reading frame; n.m.r., nuclear magnetic resonance; bp, base-pair(s); kb, 103 base-pairs; MHV, mouse hepatitis virus
Footnotes
This work was supported by an AFRC link grant, LRG 171, awarded to S.C.I.
References
- Arnott S., Hukins D.W.L., Dover S.D. Optimised parameters for RNA double-helices. Biochem. Biophys. Res. Commun. 1972;48:1392–1399. doi: 10.1016/0006-291x(72)90867-4. [DOI] [PubMed] [Google Scholar]
- Birnboim H.C., Doly J. A rapid alkaline extraction procedure for screening recombinant plasmid DNA. Nucl. Acids Res. 1979;7:1513–1523. doi: 10.1093/nar/7.6.1513. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Bredenbeek P.J., Pachuk C.J., Noten A.F.H., Charité J., Luytjes W., Weiss S.R., Spaan W.J.M. The primary structure and expression of the second open reading frame of the polymerase gene of the coronavirus MHV-A59; a highly conserved polymerase is expressed by an efficient ribosomal frameshifting mechanism. Nucl. Acids Res. 1990;18:1825–1832. doi: 10.1093/nar/18.7.1825. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Brierley I., Boursnell M.E.G., Binns M.M., Bilimoria B., Blok V.C., Brown T.D.K., Inglis S.C. An efficient ribosomal frame-shifting signal in the polymerase-encoding region of the coronavirus IBV. EMBO J. 1987;6:3779–3785. doi: 10.1002/j.1460-2075.1987.tb02713.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Brierley I., Digard P., Inglis S.C. Characterisation of an efficient coronavirus ribosomal frame-shifting signal: requirement for an RNA pseudoknot. Cell. 1989;57:537–547. doi: 10.1016/0092-8674(89)90124-4. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Boursnell M.E.G., Brown T.D.K., Foulds I.J., Green P.F., Tomley F.M., Binns M.M. Completion of the sequence of the genome of the coronavirus avian infectious bronchitis virus. J. Gen. Virol. 1987;68:57–77. doi: 10.1099/0022-1317-68-1-57. [DOI] [PubMed] [Google Scholar]
- Craigen W.J., Caskey C.T. Translational frameshifting: where will it stop? Cell. 1987;50:1–2. doi: 10.1016/0092-8674(87)90652-0. [DOI] [PubMed] [Google Scholar]
- Davies R.W., Waring F.B., Ray J.A., Brown T.A., Scazzocchio C. Making ends meet: a model for RNA splicing in fungal mitochondria. Nature (London) 1982;300:719–724. doi: 10.1038/300719a0. [DOI] [PubMed] [Google Scholar]
- Deckman I.C., Thomas M.S., Draper D.E. S4-α-mRNA translation regulation complex 1. Thermodynamics of formation. J. Mol. Biol. 1987;196:313–332. doi: 10.1016/0022-2836(87)90692-9. [DOI] [PubMed] [Google Scholar]
- Dotto G.P., Enea V., Zinder N.D. Functional analysis of bacteriophage f1 intergenic region. Virology. 1981;114:463–473. doi: 10.1016/0042-6822(81)90226-9. [DOI] [PubMed] [Google Scholar]
- Dumas P., Moras D., Florentz C., Geige R., Verlaan P., van Belkum A., Pleij C.W.A. 3-D graphics modelling of the tRNA-like 3′ end of turnip yellow mosaic virus RNA: structural and functional implications. J. Biomol. Struct. Dynam. 1987;4:707–728. doi: 10.1080/07391102.1987.10507674. [DOI] [PubMed] [Google Scholar]
- Hames B.D. An introduction to polyacrylamide gel electrophoresis. In: Hames B.D., Rickwood D., editors. Gel Electrophoresis of Proteins—A Practical Approach. IRL Press; Oxford: 1981. pp. 1–91. [Google Scholar]
- Jacks T., Varmus H.E. Expression of the Rous sarcoma virus pol gene by ribosomal frameshifting. Science. 1985;230:1237–1242. doi: 10.1126/science.2416054. [DOI] [PubMed] [Google Scholar]
- Jacks T., Townsley K., Varmus H.E., Majors J. Vol. 84. 1987. Two efficient ribosomal frameshifting events are required for synthesis of mouse mammary tumor virus gag-related polyproteins; pp. 4298–4302. (Proc. Nat. Acad. Sci., U.S.A.). [DOI] [PMC free article] [PubMed] [Google Scholar]
- Jacks T., Madhani H.D., Masiarz F.R., Varmus H.E. Signals for ribosomal frameshifting in the Rous sarcoma virus gag-pol region. Cell. 1988;55:447–458. doi: 10.1016/0092-8674(88)90031-1. [DOI] [PMC free article] [PubMed] [Google Scholar]
- James B.D., Olsen G.J., Liu J., Pace N.R. The secondary structure of ribonuclease P RNA, the catalytic element of a ribonucleoprotein enzyme. Cell. 1988;52:19–26. doi: 10.1016/0092-8674(88)90527-2. [DOI] [PubMed] [Google Scholar]
- Joshi R.L., Joshi S., Chapeville F., Haenni A.L. tRNA-like structures of plant viral RNAs: conformational requirements for adenylation and aminoacetylation. EMBO J. 1983;2:1123–1127. doi: 10.1002/j.1460-2075.1983.tb01556.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Krieg P.A., Melton D.A. Functional messenger RNAs are produced by SP6 in vitro transcription of cloned cDNAs. Nucl. Acids Res. 1984;12:7057–7071. doi: 10.1093/nar/12.18.7057. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Kunkel T.A. Vol. 82. 1985. Rapid and efficient site-specific mutagenesis without phenotypic selection; pp. 488–492. (Proc. Nat. Acad. Sci., U.S.A.). [DOI] [PMC free article] [PubMed] [Google Scholar]
- Maniatis T., Fritsch E.F., Sambrook J. Cold Spring Harbor Laboratory Press; Cold Spring Harbour, NY: 1982. (Molecular Cloning: A Laboratory Manual). [Google Scholar]
- Mans R.M.W., Guerrier-Takada C., Altman S., Pleij C.W.A. Interaction of RNase P from Escherichia coli with pseudoknotted structures in viral RNAs. Nucl. Acids Res. 1990;18:3479–3487. doi: 10.1093/nar/18.12.3479. [DOI] [PMC free article] [PubMed] [Google Scholar]
- McPheeters D.S., Stormo G.D., Gold L. Autogenous regulatory site on the bacteriophage T4 gene 32 messenger RNA. J. Mol. Biol. 1988;201:517–535. doi: 10.1016/0022-2836(88)90634-1. [DOI] [PubMed] [Google Scholar]
- Moazed D., Noller H.F. Interaction of antibiotics with functional sites in 16 S ribosomal RNA. Nature (London) 1987;327:389–394. doi: 10.1038/327389a0. [DOI] [PubMed] [Google Scholar]
- Moore R., Dixon M., Smith R., Peters G., Dickson C. Complete nucleotide sequence of a milk-transmitted mouse mammary tumor virus: two frameshift suppression events required for translation of gag and pol. J. Virol. 1987;61:480–490. doi: 10.1128/jvi.61.2.480-490.1987. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Philippe C., Portier C., Mougel M., Grunberg-Manago M., Ebel J.P., Ehresmann B., Ehresmann C. Target site of Escherichia coli ribosomal protein S15 on its messenger RNA. J. Mol. Biol. 1990;211:415–426. doi: 10.1016/0022-2836(90)90362-P. [DOI] [PubMed] [Google Scholar]
- Pleij C.W.A. Pseudoknots: a new motif in the RNA game. Trends Biochem. Sci. 1990;15:143–147. doi: 10.1016/0968-0004(90)90214-v. [DOI] [PubMed] [Google Scholar]
- Pleij C.W.A., Bosch L. RNA pseudoknots: structure, detection and prediction. Meth. Enzymol. 1989;180:289–303. doi: 10.1016/0076-6879(89)80107-7. [DOI] [PubMed] [Google Scholar]
- Pleij C.W.A., Rietveld K., Bosch L. A new principle of RNA folding based on pseudoknotting. Nucl. Acids Res. 1985;13:1717–1731. doi: 10.1093/nar/13.5.1717. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Puglisi J.D., Wyatt J.R., Tinoco I. Conformation of an RNA pseudoknot. J. Mol. Biol. 1990;214:437–453. doi: 10.1016/0022-2836(90)90192-O. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Rietveld K., van Poelgeest R., Pleij C.W.A., van Boon J.H., Bosch L. The tRNA-like structure at the 3′ terminus of turnip yellow mosaic virus RNA. Differences and similarities with canonical tRNA. Nucl. Acids Res. 1982;10:1929–1946. doi: 10.1093/nar/10.6.1929. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Rietveld K., Pleij C.W.A., Bosch L. Three dimensional models of the tRNA-like 3′ termini of some plant viral RNAs. EMBO J. 1983;2:1079–1085. doi: 10.1002/j.1460-2075.1983.tb01549.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Rietveld K., Linschooten K., Pleij C.W.A., Bosch L. The three dimensional folding of the tRNA-like structure of tobacco mosaic virus RNA. A new building principle applied twice. EMBO J. 1984;3:2613–2619. doi: 10.1002/j.1460-2075.1984.tb02182.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Russel M., Kidd S., Kelley M.R. An improved filamentous helper phage for generating single-stranded plasmid DNA. Gene. 1986;45:333–338. doi: 10.1016/0378-1119(86)90032-6. [DOI] [PubMed] [Google Scholar]
- Saenger W. Principles of Nucleic Acids Structures. Springer-Verlag; New York: 1984. Springer Advanced Texts in Chemistry. chap. 15. [Google Scholar]
- Sanger F., Nicklen S., Coulson A.R. Vol. 74. 1977. DNA sequencing with chain-terminating inhibitors; pp. 5463–5467. (Proc. Nat. Acad. Sci., U.S.A.). [DOI] [PMC free article] [PubMed] [Google Scholar]
- Tang C.K., Draper D.E. Unusual mRNA pseudoknot structure is recognised by a protein translational repressor. Cell. 1989;57:531–536. doi: 10.1016/0092-8674(89)90123-2. [DOI] [PubMed] [Google Scholar]
- ten Dam E.B., Pleij C.W.A., Bosch L. RNA pseudoknots: translational frameshifting and read-through on viral RNAs. Virus Genes. 1990;4:121–136. doi: 10.1007/BF00678404. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Turner D.H., Sugimoto N., Freier S.M. RNA structure prediction. Annu. Rev. Biophys. Biophys. Chem. 1988;17:167–192. doi: 10.1146/annurev.bb.17.060188.001123. [DOI] [PubMed] [Google Scholar]
- van Belkum A., Abrahams J.-P., Pleij C.W.A., Bosch L. Five pseudoknots are present at the 204 nucleotides long 3′ non-coding region of tobacco mosaic virus RNA. Nucl. Acids Res. 1985;13:7673–7686. doi: 10.1093/nar/13.21.7673. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Wyatt J.R., Puglisi J.D., Tinoco I. RNA pseudoknots; stability and loop size requirements. J. Mol. Biol. 1990;214:455–470. doi: 10.1016/0022-2836(90)90193-P. [DOI] [PubMed] [Google Scholar]
- Yanisch-Perron C., Vieira J., Messing J. Improved M13 phage cloning vectors and host strains: nucleotide sequences of the M13 mp18 and pUC19 vectors. Gene. 1985;33:103–119. doi: 10.1016/0378-1119(85)90120-9. [DOI] [PubMed] [Google Scholar]
- Young J.F., Desselberger U., Graves P., Palese P., Shatzman A., Rosenberg M. Cloning and expression of influenza virus genes. In: Laver W.G., editor. The Origin of Pandemic Influenza Viruses. Elsevier Science; Amsterdam: 1983. pp. 129–138. [Google Scholar]