title: Characterization of wild-type and alternate transcription termination signals in the Rift Valley fever virus genome.
abstract: Rift Valley fever (RVF) is a mosquito-borne zoonotic disease caused by a phlebovirus of the family Bunyaviridae, which affects humans and ruminants in Africa and the Middle East. RFV virus (RVFV) possesses a single-stranded tripartite RNA genome of negative/ambisense polarity. The S segment utilizes the ambisense strategy and codes for two proteins, the N nucleoprotein and the nonstructural NSs protein, in opposite orientations. The two open reading frames (ORFs) are separated by an intergenic region (IGR) highly conserved among strains and containing a motif, 5'-GCUGC-3', present on the genome and antigenome, which was shown previously to play a role in transcription termination (C. G. Albarino, B. H. Bird, and S. T. Nichol, J. Virol. 81:5246-5256, 2007; T. Ikegami, S. Won, C. J. Peters, and S. Makino, J. Virol. 81:8421-8438, 2007). Here, we created recombinant RVFVs with mutations or deletions in the IGR and showed that the substitution of the motif sequence by a series of five A's inactivated transcription termination at the wild-type site but allowed the transcriptase to recognize another site with the consensus sequence present in the opposite ORF. Similar situations were observed for mutants in which the motif was still present in the IGR but located close to the stop codon of the translated ORF, supporting a model in which transcription is coupled to translation and translocating ribosomes abrogate transcription termination. Our data also showed that the signal tolerated some sequence variations, since mutation into 5'-GCAGC-3' was functional, and 5'-GUAGC-3' is likely the signal for the termination of the 3' end of the L mRNA.
authors.affiliation: Institut Pasteur, Unité de Génétique Moléculaire des Bunyavirus, 25 rue du Dr. Roux, Paris, France.
authors.forename: Estelle
authors.initials: E
authors.lastname: Lara
authors.forename: Agnès
authors.initials: A
authors.lastname: Billecocq
authors.forename: Psylvia
authors.initials: P
authors.lastname: Leger
authors.forename: Michèle
authors.initials: M
authors.lastname: Bouloy
mesh_terms: D000349:Africa; D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D002522:Chlorocebus aethiops; D021901:DNA, Intergenic / Q000235:genetics*; D004279:DNA, Viral / Q000235:genetics; D015967:Gene Expression Regulation, Viral; D016679:Genome, Viral; D008969:Molecular Sequence Data; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000235:genetics; D012367:RNA, Viral / Q000235:genetics; D012295:Rift Valley Fever / Q000235:genetics / Q000821:virology; D012296:Rift Valley fever virus / Q000235:genetics*; D012689:Sequence Homology, Nucleic Acid; D013728:Terminator Regions, Genetic / Q000235:genetics*; D014158:Transcription, Genetic; D014709:Vero Cells
chemical_list: D021901:DNA, Intergenic; D004279:DNA, Viral; D012333:RNA, Messenger; D012367:RNA, Viral