scholarly journals Essential and Dispensable Virus-Encoded Replication Elements Revealed by Efforts To Develop Hypoviruses as Gene Expression Vectors

2000 ◽  
Vol 74 (16) ◽  
pp. 7568-7577 ◽  
Author(s):  
Nobuhiro Suzuki ◽  
Lynn M. Geletka ◽  
Donald L. Nuss
Keyword(s):  
Gene Expression ◽  
Fluorescent Protein ◽  
Cryphonectria Parasitica ◽  
Expression Vectors ◽  
Green Fluorescent Protein Gene ◽  
Reading Frame ◽  
Chestnut Blight Fungus ◽  
Virulence Attenuation ◽  
Foreign Genes ◽  
Green Fluorescent

ABSTRACT We have investigated whether hypoviruses, viral agents responsible for virulence attenuation (hypovirulence) of the chestnut blight fungusCryphonectria parasitica, could serve as gene expression vectors. The infectious cDNA clone of the prototypic hypovirus CHV1-EP713 was modified to generate 20 different vector candidates. Although transient expression was achieved for a subset of vectors that contained the green fluorescent protein gene from Aequorea victoria, long-term expression (past day 8) was not observed for any vector construct. Analysis of viral RNAs recovered from transfected fungal colonies revealed that the foreign genes were readily deleted from the replicating virus, although small portions of foreign sequences were retained by some vectors after months of replication. However, the results of vector viability and progeny characterization provided unexpected new insights into essential and dispensable elements of hypovirus replication. The N-terminal portion (codons 1 to 24) of the 5′-proximal open reading frame (ORF), ORF A, was found to be required for virus replication, while the remaining 598 codons of this ORF were completely dispensable. Substantial alterations were tolerated in the pentanucleotide UAAUG that contains the ORF A termination codon and the overlapping putative initiation codon of the second of the two hypovirus ORFs, ORF B. Replication competence was maintained following either a frameshift mutation that caused a two-codon extension of ORF A or a modification that produced a single-ORF genomic organization. These results are discussed in terms of determinants of hypovirus replication, the potential utility of hypoviruses as gene expression vectors, and possible mechanisms by which hypoviruses recognize and delete foreign sequences.

scholarly journals Expression of Foreign Proteins by Poliovirus Polyprotein Fusion: Analysis of Genetic Stability Reveals Rapid Deletions and Formation of Cardioviruslike Open Reading Frames

1998 ◽  
Vol 72 (1) ◽  
pp. 20-31 ◽  
Author(s):  
Steffen Mueller ◽  
Eckard Wimmer
Keyword(s):  
Fluorescent Protein ◽  
Growth Cycle ◽  
Open Reading Frames ◽  
Expression Vectors ◽  
Green Fluorescent Protein Gene ◽  
Published Data ◽  
Gene Encoding ◽  
Genomic Rnas ◽  
Reading Frame ◽  
Green Fluorescent

ABSTRACT Using a strategy developed by R. Andino, D. Silvera, S. D. Suggett, P. I. Achacoso, C. J. Miller, D. Baltimore, and M. B. Feinberg (Science 265:1448–1451, 1994), we constructed recombinant polioviruses by fusing the open reading frame (ORF) of the green fluorescent protein gene (gfp) of Aequorea victoria or the gag gene (encoding p17-p24) of human immunodeficiency virus type 1 (HIV-1) to the N terminus of the poliovirus polyprotein. All poliovirus expression vectors constructed by us and those obtained from Andino et al. were found to be severely impaired in viral replication and genetically unstable. Upon replication, inserted sequences were rapidly deleted as early as the first growth cycle in HeLa cells. However, the vector viruses did not readily revert to the wild-type sequence but rather retained some of the insert plus the artificial 3Cpro/3CDprocleavage site, engineered between the heterologous sequence and the poliovirus polyprotein, to give rise to genotypes reminiscent of cardioviruses. These virus variants that carry a small leader polypeptide were now relatively stable, and they grew better than their progenitor strains. Reverse transcription followed by PCR and sequence analysis of the genomic RNAs reproducibly revealed a few preferred genotypes among the isolated deletion variants. The remaining truncated inserts were retained through subsequent passages. In the immediate vicinity of the deletion borders, we observed short direct sequence repeats that we propose are involved in aligning RNA strands for illegitimate (nonhomologous) RNA recombination during minus-strand synthesis. On the basis of our results, which are at variance with published data, the utility of poliovirus vectors to express proteins >10 kDa in size through fusion with the polyprotein needs to be reevaluated.

scholarly journals Hypovirus Papain-Like Protease p29 Suppresses RNA Silencing in the Natural Fungal Host and in a Heterologous Plant System

2006 ◽  
Vol 5 (6) ◽  
pp. 896-904 ◽  
Author(s):  
Gerrit C. Segers ◽  
Rene van Wezel ◽  
Xuemei Zhang ◽  
Yiguo Hong ◽  
Donald L. Nuss
Keyword(s):  
Rna Silencing ◽  
Defense Mechanism ◽  
Fluorescent Protein ◽  
Cryphonectria Parasitica ◽  
Fungal Host ◽  
Chestnut Blight Fungus ◽  
Systemic Spread ◽  
Green Fluorescent ◽  
Fungal Viruses ◽  
Suppressor Of Rna Silencing

ABSTRACT Virulence-attenuating hypoviruses of the species Cryphonectria hypovirus 1 (CHV1) encode a papain-like protease, p29, that shares similarities with the potyvirus-encoded suppressor of RNA silencing HC-Pro. We now report that hypovirus CHV1-EP713-encoded p29 can suppress RNA silencing in the natural host, the chestnut blight fungus Cryphonectria parasitica. Hairpin RNA-triggered silencing was suppressed in C. parasitica strains expressing p29, and transformation of a transgenic green fluorescent protein (GFP)-silenced strain with p29 resulted in an increased number of transformants with elevated GFP expression levels. The CHV1-EP713 p29 protein was also shown to suppress both virus-induced and agroinfiltration-induced RNA silencing and systemic spread of silencing in GFP-expressing transgenic Nicotiana benthamiana line 16c plants. The demonstration that a mycovirus encodes a suppressor of RNA silencing provides circumstantial evidence that RNA silencing in fungi may serve as an antiviral defense mechanism. The observation that a phylogenetically conserved protein of related plant and fungal viruses functions as a suppressor of RNA silencing in both fungi and plants indicates a level of conservation of the mechanisms underlying RNA silencing in these two groups of organisms.

scholarly journals The Green Fluorescent Protein Gene Functions as a Reporter of Gene Expression in Phanerochaete chrysosporium

2001 ◽  
Vol 67 (2) ◽  
pp. 948-955 ◽  
Author(s):  
Biao Ma ◽  
Mary B. Mayfield ◽  
Michael H. Gold
Keyword(s):  
Gene Expression ◽  
Green Fluorescent Protein ◽  
Phanerochaete Chrysosporium ◽  
Fluorescent Protein ◽  
Schizophyllum Commune ◽  
Extracellular Fluid ◽  
Gene Promoter ◽  
Green Fluorescent Protein Gene ◽  
Cell Extracts ◽  
Green Fluorescent

ABSTRACT The enhanced green fluorescent protein (GFP) gene (egfp) was used as a reporter of gene expression driven by the glyceraldehyde-p-dehydrogenase (gpd) gene promoter and the manganese peroxidase isozyme 1 (mnp1) gene promoter in Phanerochaete chrysosporium. Four different constructs were prepared. pUGGM3′ and pUGiGM3′ contain the P. chrysosporium gpd promoter fused upstream of the egfpcoding region, and pUMGM3′ and pUMiGM3′ contain the P. chrysosporium mnp1 promoter fused upstream of theegfp gene. In all constructs, the egfp gene was followed by the mnp1 gene 3′ untranslated region. In pUGGM3′ and pUMGM3′, the promoters were fused directly withegfp, whereas in pUGiGM3′ and pUMiGM3′, following the promoters, the first exon (6 bp), the first intron (55 bp), and part of the second exon (9 bp) of the gpd gene were inserted at the 5′ end of the egfp gene. All constructs were ligated into a plasmid containing the ura1 gene of Schizophyllum commune as a selectable marker and were used to transform a Ural1 auxotrophic strain of P. chrysosporium to prototrophy. Crude cell extracts were examined for GFP fluorescence, and where appropriate, the extracellular fluid was examined for MnP activity. The transformants containing a construct with an intron 5′ of theegfp gene (pUGiGM3′ and pUMiGM3′) exhibited maximal fluorescence under the appropriate conditions. The transformants containing constructs with no introns exhibited minimal or no fluorescence. Northern (RNA) blots indicated that the insertion of a 5′ intron resulted in more egfp RNA than was found in transformants carrying an intronless egfp. These results suggest that the presence of a 5′ intron affects the expression of theegfp gene in P. chrysosporium. The expression of GFP in the transformants carrying pUMiGM3′ paralled the expression of endogenous mnp with respect to nitrogen and Mn levels, suggesting that this construct will be useful in studyingcis-acting elements in the mnp1 gene promoter.

scholarly journals Characterization of a Neuraminidase-Deficient Influenza A Virus as a Potential Gene Delivery Vector and a Live Vaccine

2004 ◽  
Vol 78 (6) ◽  
pp. 3083-3088 ◽  
Author(s):  
Kyoko Shinya ◽  
Yutaka Fujii ◽  
Hiroshi Ito ◽  
Toshihiro Ito ◽  
Yoshihiro Kawaoka
Keyword(s):  
Influenza Virus ◽  
Influenza A Virus ◽  
Influenza A ◽  
Fluorescent Protein ◽  
Cultured Cells ◽  
Mutant Cell ◽  
Wild Type Virus ◽  
Reading Frame ◽  
Foreign Genes ◽  
Green Fluorescent

ABSTRACT We recently identified a packaging signal in the neuraminidase (NA) viral RNA (vRNA) segment of an influenza A virus, allowing us to produce a mutant virus [GFP(NA)-Flu] that lacks most of the NA open reading frame but contains instead the gene encoding green fluorescent protein (GFP). To exploit the expanding knowledge of vRNA packaging signals to establish influenza virus vectors for the expression of foreign genes, we studied the replicative properties of this virus in cell culture and mice. Compared to wild-type virus, GFP(NA)-Flu was highly attenuated in normal cultured cells but was able to grow to a titer of >106 PFU/ml in a mutant cell line expressing reduced levels of sialic acid on the cell surface. GFP expression from this virus was stable even after five passages in the latter cells. In intranasally infected mice, GFP was detected in the epithelial cells of nasal mucosa, bronchioles, and alveoli for up to 4 days postinfection. We attribute the attenuated growth of GFP(NA)-Flu to virion aggregation at the surface of bronchiolar epithelia. In studies to test the potential of this mutant as a live attenuated influenza vaccine, all mice vaccinated with ≥105 PFU of GFP(NA)-Flu survived when challenged with lethal doses of the parent virus. These results suggest that influenza virus could be a useful vector for expressing foreign genes and that a sialidase-deficient virus may offer an alternative to the live influenza vaccines recently approved for human use.

Improvement of TA Cloning Method to Facilitate Direct Directional Cloning of PCR Products

2014 ◽  
Vol 565 ◽  
pp. 3-8 ◽  
Author(s):  
Ji Gang Li ◽  
Guo Ying Han ◽  
Xiu Min Li ◽  
Jiao Jiao Sun ◽  
Ke Jing Song ◽  
...  
Keyword(s):  
Fluorescent Protein ◽  
Pcr Primers ◽  
Expression Vectors ◽  
Green Fluorescent Protein Gene ◽  
Reaction Products ◽  
Major Disadvantage ◽  
Cloning Method ◽  
Directional Cloning ◽  
Pcr Products ◽  
Green Fluorescent

Directional cloning is a prerequisite for the construction of expression vectors in molecular biology laboratories. Although TA cloning is widely used to clone unmodified PCR (polymerase chain reaction) products, a major disadvantage of this technique is that cloning is not directional. Here we reported a novel PCR products cloning vector with one deoxythymidine overhang and one deoxycytidine overhang at two 3'-ends respectively. With the choice of nucleotides of 5'-ends of PCR primers, PCR products can be cloned to this vector both directly and directionally. The feasibility and efficacy of this cloning method were confirmed by using a pET-17b derivative vector and a green fluorescent protein gene (EGFP) and a red fluorescent protein reporter (Ds-Red) gene. This cloning strategy may be useful in the high-throughput construction of expression vectors and could be viewed as an interesting improvement of existing TA cloning method.

scholarly journals Effects of L1-ORF2 fragments on green fluorescent protein gene expression

2009 ◽  
Vol 32 (4) ◽  
pp. 688-696 ◽  
Author(s):  
Xiu-Fang Wang ◽  
Xia Jin ◽  
Xiaoyan Wang ◽  
Jing Liu ◽  
Jingjing Feng ◽  
...  
Keyword(s):  
Gene Expression ◽  
Green Fluorescent Protein ◽  
Protein Gene ◽  
Fluorescent Protein ◽  
Green Fluorescent Protein Gene ◽  
Green Fluorescent

scholarly journals Measles virus minigenomes encoding two autofluorescent proteins reveal cell-to-cell variation in reporter expression dependent on viral sequences between the transcription units

2007 ◽  
Vol 88 (10) ◽  
pp. 2710-2718 ◽  
Author(s):  
Linda J. Rennick ◽  
W. Paul Duprex ◽  
Bert K. Rima
Keyword(s):  
Gene Expression ◽  
Measles Virus ◽  
Fluorescent Protein ◽  
The Other ◽  
Green Fluorescent Protein Gene ◽  
Conserved Gene ◽  
Green Fluorescent ◽  
Single Living Cells ◽  
Cell Variation ◽  
Viral Sequences

Transcription from morbillivirus genomes commences at a single promoter in the 3′ non-coding terminus, with the six genes being transcribed sequentially. The 3′ and 5′ untranslated regions (UTRs) of the genes (mRNA sense), together with the intergenic trinucleotide spacer, comprise the non-coding sequences (NCS) of the virus and contain the conserved gene end and gene start signals, respectively. Bicistronic minigenomes containing transcription units (TUs) encoding autofluorescent reporter proteins separated by measles virus (MV) NCS were used to give a direct estimation of gene expression in single, living cells by assessing the relative amounts of each fluorescent protein in each cell. Initially, five minigenomes containing each of the MV NCS were generated. Assays were developed to determine the amount of each fluorescent protein in cells at both cell population and single-cell levels. This revealed significant variations in gene expression between cells expressing the same NCS-containing minigenome. The minigenome containing the M/F NCS produced significantly lower amounts of fluorescent protein from the second TU (TU2), compared with the other minigenomes. A minigenome with a truncated F 5′ UTR had increased expression from TU2. This UTR is 524 nt longer than the other MV 5′ UTRs. Insertions into the 5′ UTR of the enhanced green fluorescent protein gene in the minigenome containing the N/P NCS showed that specific sequences, rather than just the additional length of F 5′ UTR, govern this decreased expression from TU2.

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