Subgenomic RNAs of bamboo mosaic potexvirus-V isolate are packaged into virions.

Lee, Yun‐Shien; Lin, Biing-Yuan; Hsu, Yau‐Heiu; Chang, Ban‐Yang; Lin, Na-Sheng

doi:10.1099/0022-1317-79-7-1825

Cited by 18 publications

(14 citation statements)

References 32 publications

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“…ORF2 to ORF4, which code for triple gene block proteins of 28, 13, and 6 kDa (21, 40), respectively, are required for viral cell-to-cell movement (3,39). The product of ORF5 is the CP of 25 kDa (15). A satellite RNA (satBaMV) was found to be associated with the BaMV-V isolate (22).…”

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confidence: 99%

“…For the potexvirus group, two major sgRNAs of about 1.9 to 2.1 kb and 0.9 to 1.0 kb in size, which direct the expression of the ORF2 protein and the CP, respectively, were detected in the infected cells (7,11,15,37). Another bicistronic sgRNA of 1.4 kb, which was responsible for the translation of ORF3 and ORF4 proteins, accumulated at a very low level in the infected cells (36).…”

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confidence: 99%

“…Alignment of the putative SGPs of ORF2 protein and CP among potexviruses revealed that the conserved octanucleotide motif (3Ј-CAAUUCAA-5Ј) was located upstream from the transcription initiation sites of the sgRNAs (12,15,37). However, the nucleotide sequences and the spacing between the transcription initiation site and the octanucleotide motif vary among potexviruses (12,15). It has been shown that complementarity between the conserved octanucleotide sequence and the 3Ј terminus of minus-strand potato virus X (PVX) RNA is important for the synthesis of sgRNA (13).…”

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confidence: 99%

“…Recently, sgRNA initiation has been studied on the small template of minus-strand BMV RNA3, using purified viral RdRp complexes, which suggests that recognition of the SGP by the BMV RdRp is sequence specific (1, 30). However, the secondary structure of the SGP may also facilitate efficient sgRNA transcription in vivo (1).For the potexvirus group, two major sgRNAs of about 1.9 to 2.1 kb and 0.9 to 1.0 kb in size, which direct the expression of the ORF2 protein and the CP, respectively, were detected in the infected cells (7,11,15,37). Another bicistronic sgRNA of 1.4 kb, which was responsible for the translation of ORF3 and ORF4 proteins, accumulated at a very low level in the infected cells (36).…”

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confidence: 99%

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Generation of Subgenomic RNA Directed by a Satellite RNA Associated with Bamboo Mosaic Potexvirus: Analyses of Potexvirus Subgenomic RNA Promoter

Lee

Hsu

Lin

2000

J Virol

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Satellite RNA of bamboo mosaic potexvirus (satBaMV), a single-stranded positive-sense RNA encoding a nonstructural protein of 20 kDa (P20), depends on bamboo mosaic potexvirus (BaMV) for replication and encapsidation. A full-length cDNA clone of satBaMV was used to examine the sequences required for the synthesis of potexvirus subgenomic RNAs (sgRNAs). Subgenomic promoter-like sequences (SGPs), 107 nucleotides (nt) upstream from the capsid protein (CP) gene of BaMV-V, were inserted upstream of the start codon of the P20 gene of satBaMV. Insertion of SGPs gave rise to the synthesis of sgRNA of satBaMV in protoplasts of Nicotiana benthamiana and leaves of Chenopodium quinoa when coinoculated with BaMV-V genomic RNA. Moreover, both the satBaMV cassette and its sgRNA were encapsidated. From analysis of the SGPs by deletion mutation, we concluded that an SGP contains one core promoterlike sequence (nt ؊30 through ؉16), two upstream enhancers (nt ؊59 through ؊31 and ؊91 through ؊60), and one downstream enhancer (nt ؉17 through ؉52), when the transcription initiation site is taken as ؉1. Site-directed mutagenesis and compensatory mutation to disrupt and restore potential base pairing in the core promoter-like sequence suggest that the stem-loop structure is important for the function of SGP in vivo. Likewise, the insertion of a putative SGP of the BaMV open reading frame 2 gene or a heterologous SGP of potato virus X resulted in generation of an sgRNA. The satBaMV cassette should be a useful tool to gain insight into sequences required for the synthesis of potexvirus sgRNAs.The production of subgenomic RNAs (sgRNAs) is one of the strategies by which internally located open reading frames (ORFs) of multicistronic RNA virus may be expressed and regulated during replication. The capsid proteins (CPs) of alpha-like superfamily viruses are expressed by sgRNA transcription (24). The proteins encoded by the triple gene block of potex-, carla-, furo-, and hordeiviruses and the movement proteins of tobamo-and tombusviruses are also expressed by the same strategy (24). Several mechanisms are proposed for the transcription of sgRNAs. The first is leader-primed transcription, which occurs in the production of coronavirus sgRNAs. This process involves fusion of noncontinuous sequences from the 5Ј leader sequences to the sgRNA by a discontinuous process (14). Recently, a new model for coronavirus transcription was proposed. This model predicts that subgenome-length negative strands containing the common 5Ј leader sequence were directly derived from genome RNA and served as a template for the production of sgRNA (27). The second mechanism proposed for transcription of sgRNAs is exemplified by transcription of RNA-mediated trans-activation. A 34-nucleotide (nt) trans-activator on red clover necrotic mosaic virus RNA2 was proposed to bind to the element upstream of the sgRNA initiation site on RNA1 and to prevent the synthesis of full-length minus-strand RNA1. This truncated minus-strand RNA1 may serve as a template for viral RNA-depen...

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confidence: 99%

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confidence: 99%

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confidence: 99%

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confidence: 99%

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Generation of Subgenomic RNA Directed by a Satellite RNA Associated with Bamboo Mosaic Potexvirus: Analyses of Potexvirus Subgenomic RNA Promoter

Lee

Hsu

Lin

2000

J Virol

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“…The small K m value of the RNA acceptor (ϳ0.4 M for ppG(C) 25 ) suggests that the whole part of the RNA substrate contributes to the binding. The genomic RNA of BaMV has a guanylate residue at its 5Ј end, whereas the ϳ2-and ϳ1-kilobase subgenomic RNAs start with adenylate (22). It is, therefore, interesting to know whether the capping efficiency of the viral RNA would actually be affected by the type of nucleotide at its very 5Ј end and whether the speculative difference in the capping efficiency is involved in mechanisms of regulating the viral protein expression.…”

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mRNA Guanylation Catalyzed by the S-Adenosylmethionine-dependent Guanylyltransferase of Bamboo Mosaic Virus

Huang¹,

Hsu

Han

et al. 2005

Journal of Biological Chemistry

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The S-adenosylmethionine-dependent guanylyltransferase of bamboo mosaic virus belongs to a novel class of mRNA capping enzymes distantly conserved in Alphavirus-like superfamily. The reaction sequence of the viral enzyme has been proposed comprising steps of 1) binding of GTP and S-adenosylmethionine, 2) formation of m 7 GTP and S-adenosylhomocysteine, 3) formation of the covalent (Enzyme-m 7 GMP) intermediate, and 4) transfer of m 7 GMP from the intermediate to the RNA acceptor. In this study the acceptor specificity of the viral enzyme was characterized. The results show that adenylate or guanylate with 5-diphosphate group is an essential feature for acceptors, which can be RNA or mononucleotide, to receive m 7 GMP. The transfer rate of m 7 GMP to guanylate is greater than to adenylate by a factor of ϳ3, and the K m value for mononucleotide acceptor is ϳ10 3 -fold higher than that for RNA. The capping efficiency of the viral genomic RNA transcript depends on the length of the transcript and the formation of a putative stemloop structure, suggesting that mRNA capping process may participate in regulating the viral gene expression.The 5Ј cap structure, m 7 G(5Ј)ppp(5Ј)N, of mRNA serves as a recognition site for ribosome binding in translation and is important for the stability of mRNA against the attack of 5Ј exonuclease in eukaryotic cells. A series of three nuclear enzymatic activities is responsible for the formation of the cap structure (1). First, the ␥-phosphate at the 5Ј end of nascent mRNA is removed by RNA 5Ј-triphosphatase; second, the GMP moiety of GTP molecule is transferred to the 5Ј-diphosphate end of the RNA via a 5Ј-5Ј linkage by guanylyltransferase; and finally, a methyl group is added to N7 of the transferred guanylate from S-adenosylmethionine (AdoMet) 1 by methyltransferase. The cap formation pathway for viruses within the Alphavirus-like superfamily differs from the nuclear mechanism in that methylation of GTP occurs before transguanylation; in other words, m 7 GMP, rather than GMP, is transferred to the 5Ј end of the 5Ј-diphosphate RNA during the cap formation process. This distinctive mRNA capping reaction is catalyzed by a group of distantly conserved AdoMet-dependent guanylyltransferases that were identified in Semliki Forest virus (2), hepatitis E virus (3), tobacco mosaic virus (4), brome mosaic virus (5, 6), and bamboo mosaic virus (BaMV) (7). Together with other characteristics such as their membrane-association nature and distinctive protein primary structures, this class of enzyme represents a novel mRNA capping enzyme different from those evolutionally conserved guanylyltransferases and methyltransferases in DNA viruses, metazoans, and fungi. Although the critical roles of the conserved amino acids in the enzymatic activities of the enzyme of Semliki Forest virus (8) and BaMV (9) have been addressed, the molecular mechanism of this class of enzyme is far from being understood.BaMV, a member of Alphavirus-like superfamily, has a ϳ6.4-kilobase positive-strand RNA genome with a cap s...

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The Positive Sense Single Stranded RNA Viruses

Duin¹,

Wor²,

Buck³

et al. 2005

Virus Taxonomy

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Subgenomic RNAs of bamboo mosaic potexvirus-V isolate are packaged into virions.

Cited by 18 publications

References 32 publications

Generation of Subgenomic RNA Directed by a Satellite RNA Associated with Bamboo Mosaic Potexvirus: Analyses of Potexvirus Subgenomic RNA Promoter

Generation of Subgenomic RNA Directed by a Satellite RNA Associated with Bamboo Mosaic Potexvirus: Analyses of Potexvirus Subgenomic RNA Promoter

mRNA Guanylation Catalyzed by the S-Adenosylmethionine-dependent Guanylyltransferase of Bamboo Mosaic Virus

The Positive Sense Single Stranded RNA Viruses

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