In vitro mutagenesis of biologically active transcripts of beet necrotic yellow vein virus RNA 2: Evidence that a domain of the 75-kDa readthrough protein is important for efficient virus assembly

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 89; no. 13; pp. 5715 - 5719
• Main Authors: Schmitt, C. (Universite Louis Pasteur, Strasbourg, France), Balmori, E, Jonard, G, Richards, K.E, Guilley, H
• Format: Journal Article
• Language: English
• Published: Washington, DC National Academy of Sciences of the United States of America 01-07-1992; National Acad Sciences; National Academy of Sciences
• Subjects: Base Sequence; beet necrotic yellow vein virus; Biochemistry, Molecular Biology; Biological and medical sciences; Capsid - genetics; Capsid proteins; DNA - genetics; Flowers & plants; Fundamental and applied biological sciences. Psychology; Genes; Lesions; Life Sciences; Microbiology; Molecular Sequence Data; MUTACION; Mutagenesis, Site-Directed; MUTATION; Oligodeoxyribonucleotides - chemistry; Open reading frames; Peptide Chain Termination, Translational; Plant Diseases - microbiology; Plant Viruses - genetics; Plant Viruses - pathogenicity; PROTEINAS; PROTEINE; Proteins; Replicative cycle, interference, host-virus relations, pathogenicity, miscellaneous strains; Ribonucleic acid; RNA; RNA, Viral - genetics; Stop codon; Structure-Activity Relationship; Viral RNA; Virions; Virology; VIRUS; VIRUS DE LAS PLANTAS; VIRUS DES VEGETAUX; Virus Replication; Viruses; Virus; Infection; Furovirus; Antitermination; Virus multiplication; Plant pathogen; Molecular assembly; Site directed mutagenesis; Genetical translation; Beet necrotic yellow vein virus
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.89.13.5715

RNA 2 of the multipartite genome of beet necrotic yellow vein virus carries the cistron for 21-kDa viral coat protein at its 5' extremity. The amber termination codon of the coat protein cistron undergoes suppression approximately 10% of the time so that translation continues into an adjacent 54-kDa open reading frame, yielding a 75-kDa readthrough protein. The roles of coat protein and the readthrough protein in infection were investigated with biologically active transcripts of RNA 2. Much of the coat protein cistron of the RNA 2 transcript could be deleted without interfering with viral replication and local lesion formation on leaves, although formation of the rodshaped virions did not occur. Mutants in which the amber coat protein termination codon was replaced with an ochre codon or a tyrosine codon were also viable. The ochre codon was suppressed both in vitro and in planta. The mutant containing the tyrosine substitution produced only the 75-kDa readthrough protein and was deficient in viral assembly. Deletions in the 54-kDa readthrough domain were also viable in planta but had different effects on virus assembly. A deletion in the C-terminal portion of the readthrough domain did not interfere with RNA packaging but, unexpectedly, deletions in the N-terminal portion were assembly deficient, although 21-kDa coat protein was produced in planta. Thus, the 75-kDa protein can apparently intervene in virion assembly even though it has not been detected in purified virions