Effects of deletions in the N-terminal basic arm of brome mosaic virus coat protein on RNA packaging and systemic infection

Sacher, R. F.; Ahlquist, Paul

doi:10.1128/jvi.63.11.4545-4552.1989

Cited by 128 publications

(53 citation statements)

References 48 publications

(56 reference statements)

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“…3B and C). This is in keeping with prior results from yeast and plant cells that selective packaging by BMV CP (31) removes positive-strand RNA from the pool of templates available for replicase copying, reducing the accumulation of negative-strand RNA (20,31,37,42,48).…”

Section: Resultssupporting

confidence: 88%

See 1 more Smart Citation

Mutual Interference between Genomic RNA Replication and Subgenomic mRNA Transcription in Brome Mosaic Virus

Grdzelishvili

García-Ruíz

Watanabe

et al. 2005

J Virol

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Replication by many positive-strand RNA viruses includes genomic RNA amplification and subgenomic mRNA (sgRNA) transcription. For brome mosaic virus (BMV), both processes occur in virus-induced, membrane-associated compartments, require BMV replication factors 1a and 2a, and use negative-strand RNA3 as a template for genomic RNA3 and sgRNA syntheses. To begin elucidating their relations, we examined the interaction of RNA3 replication and sgRNA transcription in Saccharomyces cerevisiae expressing 1a and 2a, which support the full RNA3 replication cycle. Blocking sgRNA transcription stimulated RNA3 replication by up to 350%, implying that sgRNA transcription inhibits RNA3 replication. Such inhibition was independent of the sgRNA-encoded coat protein and operated in cis. We further found that sgRNA transcription inhibited RNA3 replication at a step or steps after negative-strand RNA3 synthesis, implying competition with positivestrand RNA3 synthesis for negative-strand RNA3 templates, viral replication factors, or common host components. Consistent with this, sgRNA transcription was stimulated by up to 400% when mutations inhibiting positive-strand RNA3 synthesis were introduced into the RNA3 5-untranslated region. Thus, BMV subgenomic and genomic RNA syntheses mutually interfered with each other, apparently by competition for one or more common factors. In plant protoplasts replicating all three BMV genomic RNAs, mutations blocking sgRNA transcription often had lesser effects on RNA3 accumulation, possibly because RNA3 also competed with RNA1 and RNA2 replication templates and because any increase in RNA3 replication at the expense of RNA1 and RNA2 would be self-limited by decreased 1a and 2a expression from RNA1 and RNA2.Subgenomic mRNA (sgRNA) transcription is a mechanism used by many eukaryotic RNA viruses to multiply the number of separate genes expressed and to regulate the timing and magnitude of their expression. Numerous positive-strand RNA viruses produce sgRNAs, using diverse transcription mechanisms distinguished by internal initiation or termination, continuous or discontinuous RNA synthesis, etc., to link internal open reading frames (ORFs) to a translatable 5Ј end, producing sgRNAs that are 3Ј-coterminal with the viral genomic RNA (40). Many studies have revealed cis-signals and mechanistic features of sgRNA transcription and genomic RNA replication in different positive-strand RNA viruses, but relatively little is known about how these two processes, which depend on common viral replication factors and RNA templates, are coordinated.Relevant infectious processes, such as RNA replication, sgRNA transcription, and host factor involvement, have been studied for a number of positive-strand RNA viruses, including brome mosaic virus (BMV), a member of the alphavirus superfamily. The BMV genome consists of three genomic RNAs. RNA1 and RNA2 encode viral RNA synthesis factors 1a and 2a, which are required for genome replication and sgRNA synthesis. 2a is the viral RNA polymerase, while 1a is a multifunction...

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Section: Resultssupporting

confidence: 88%

“…Relative to wt RNA3 expressing CP from sgRNA (T7-B3WT), the sgRNA mutants displayed a decrease in RNA3 positiveand negative-strand RNA3 accumulation, as reported in reference 19. However, CP expression modulates BMV RNA accumulation due to encapsidation, as shown previously (20,31,37,42,48) and in this study (Fig. 3).…”

Section: Resultssupporting

confidence: 87%

Mutual Interference between Genomic RNA Replication and Subgenomic mRNA Transcription in Brome Mosaic Virus

Grdzelishvili

García-Ruíz

Watanabe

et al. 2005

J Virol

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“…The amino terminus of many plant viral coat proteins is highly basic, and is referred to as the amino terminal "arm" [117]. The Nterminal arms are unstructured, and in the case of AMV, interfere with virus crystallization [118].…”

Section: Coat Protein-mediated Conformational Switch In Alfalfa Mosaimentioning

confidence: 99%

RNA conformational changes in the life cycles of RNA viruses, viroids, and virus-associated RNAs

Simon

Gehrke

2009

Biochimica et Biophysica Acta (BBA) - Gene Regulatory Mechanism

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The rugged nature of the RNA structural free energy landscape allows cellular RNAs to respond to environmental conditions or fluctuating levels of effector molecules by undergoing dynamic conformational changes that switch on or off activities such as catalysis, transcription or translation. Infectious RNAs must also temporally control incompatible activities and rapidly complete their life cycle before being targeted by cellular defenses. Viral genomic RNAs must switch between translation and replication, and untranslated subviral RNAs must control other activities such as RNA editing or self-cleavage. Unlike well-characterized riboswitches in cellular RNAs, the control of infectious RNA activities by altering the configuration of functional RNA domains has only recently been recognized. In this review, we will present some of these molecular rearrangements found in RNA viruses, viroids and virus-associated RNAs, relating how these dynamic regions were discovered, the activities that might be regulated, and what factors or conditions might cause a switch between conformations.

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“…RNA3 is a bicistronic RNA encoding the 3a cell-to-cell movement protein and the coat protein. Both of these proteins are required for systemic infection of BMV's natural plant hosts but are dispensable for RNA replication in a single cell (4,27,35). The 3a protein is directly translated from the 5Ј-proximal 3a gene of RNA3, whereas the 3Ј-proximal coat gene is translated from a subgenomic mRNA, RNA4, produced from the negative-strand RNA3 replication intermediate.…”

mentioning

confidence: 99%

An Alternate Pathway for Recruiting Template RNA to the Brome Mosaic Virus RNA Replication Complex

Chen

Noueiry

Ahlquist

2003

J Virol

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The multidomain RNA replication protein 1a of brome mosaic virus (BMV), a positive-strand RNA virus in the alphavirus-like superfamily, plays key roles in assembly and function of the viral RNA replication complex. 1a, which encodes RNA capping and helicase-like domains, localizes to endoplasmic reticulum membranes, recruits BMV 2a polymerase and viral RNA templates, and forms membrane-bound, capsid-like spherules in which RNA replication occurs. cis-acting signals necessary and sufficient for RNA recruitment by 1a have been mapped in BMV genomic RNA2 and RNA3. Both signals comprise an extended stem-loop whose apex matches the conserved sequence and structure of the T⌿C stem-loop in tRNAs (box B). Mutations show that this box B motif is crucial to 1a responsiveness of wild-type RNA2 and RNA3. We report here that, unexpectedly, some chimeric mRNAs expressing the 2a polymerase open reading frame from RNA2 were recruited by 1a to the replication complex and served as templates for negative-strand RNA synthesis, despite lacking the normally essential, box B-containing 5 signal. Further studies showed that this template recruitment required highefficiency translation of the RNA templates. Moreover, multiple small frameshifting insertion or deletion Brome mosaic virus (BMV) is a well-studied member of the large alphavirus-like superfamily of animal and plant positivestrand RNA viruses. The genome of BMV is divided into three capped RNAs (1, 41). RNA1 and RNA2 encode nonstructural proteins 1a and 2a, respectively, which direct RNA replication and contain domains conserved with other superfamily members (3,16,22). 1a contains an N-terminal domain with m 7 G methyltransferase and covalent GTP binding activities that are required for capping of viral RNA during RNA replication in vivo (2, 3, 26) and a C-terminal domain with all motifs of DEAD box RNA helicases (19). Mutations in the helicase-like domain cause strong defects in RNA replication (3). The central portion of 2a is similar to RNA-dependent RNA polymerases (5, 21). RNA3 is a bicistronic RNA encoding the 3a cell-to-cell movement protein and the coat protein. Both of these proteins are required for systemic infection of BMV's natural plant hosts but are dispensable for RNA replication in a single cell (4,27,35). The 3a protein is directly translated from the 5Ј-proximal 3a gene of RNA3, whereas the 3Ј-proximal coat gene is translated from a subgenomic mRNA, RNA4, produced from the negative-strand RNA3 replication intermediate.Like that of most, if not all, eukaryotic positive-strand RNA viruses, BMV RNA replication occurs on membrane-associated complexes (13,17,20,(32)(33)(34). Besides providing essential enzymatic functions for RNA replication, 1a plays key roles in the assembly and function of the BMV RNA replication complex, which is associated with endoplasmic reticulum (ER) membranes. 1a localizes to the cytoplasmic face of ER membranes in the absence of other viral factors (33) by signals residing in the N-proximal half of the protein (11). In contrast, the ...

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Effects of deletions in the N-terminal basic arm of brome mosaic virus coat protein on RNA packaging and systemic infection

Cited by 128 publications

References 48 publications

Mutual Interference between Genomic RNA Replication and Subgenomic mRNA Transcription in Brome Mosaic Virus

Mutual Interference between Genomic RNA Replication and Subgenomic mRNA Transcription in Brome Mosaic Virus

RNA conformational changes in the life cycles of RNA viruses, viroids, and virus-associated RNAs

An Alternate Pathway for Recruiting Template RNA to the Brome Mosaic Virus RNA Replication Complex

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