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I Sela

Publications and source records attributed to I Sela.

At least 19 recordsLinked to original sources
PubMed1999

Infectious RNA transcripts from grapevine virus A cDNA clone.

A full length cDNA clone of grapevine virus A (GVA) was constructed downstream from the bacteriophage T7 RNA polymerase promoter. Capped in vitro-transcribed RNA was infectious in Nicotiana benthamiana and N. clevelandii plants. Symptoms induced by the RNA transcripts or by the parental virus were indistinguishable. The infectivity of the in vitro-transcribed RNA was confirmed by serological detection of the virus coat and movement proteins and by observation of virions by electron microscopy. This is the first report of infectious RNA transcripts derived from a full-length cDNA clone of a member of the Vitivirus genus.

Cloning, Molecular↗
PubMed1995

Starvation and refeeding regulate glycogen synthase gene expression in rat liver at the posttranscriptional level.

Starvation and refeeding affect glycogen metabolism. The effects of starvation and refeeding on the level of glycogen synthase (GS) gene expression were examined in rat liver. Depletion of hepatic glycogen stores by 72 h of starvation (7% of control) was supercompensated by 24 h of refeeding a standard laboratory diet (247% of control). Upon further refeeding, glycogen concentration gradually returned to control levels after 120 h. After 72 h of starvation, GS activity and immunoreactive protein in the liver were 60-64% lower than in control rats with free access to food. After 72 h of refeeding, GS activity and immunoreactive protein returned to control values. No significant differences in GS mRNA levels were found between fed, starved and refed rats, as determined by Northern blot analysis and PCR quantification, indicating that the long-term regulation of GS gene expression in starvation and refeeding occurs via a posttranscriptional mechanism. The amount of GS mRNA associated with polyribosomes was 90% lower in starved than in fed rats. These data indicate that the efficiency of GS mRNA translation, rather than its abundance, decreases during starvation.

Animals↗
PubMed1993

Plants transformed with a cistron of a potato virus Y protease (NIa) are resistant to virus infection.

An oligonucleotide carrying signals for translation initiation in plants was engineered upstream to a cDNA clone containing nucleotides 5812-7260 of the potato virus Y (PVY) genome. This fragment contains all but the first 100 5' terminal bases of the cistron encoding one of the PVY proteases (NIa) as well as the first 251 bases of the next cistron (NIb). Nicotiana tabacum cv. SR1 plants were transformed with this fragment. The presence of the NIa sequences in transformed plants was determined by hybridization or PCR, and its expression was ascertained by reverse transcription coupled to PCR. Plants expressing NIa were self-pollinated, and the R1 kanamycin-resistant progeny were rechecked for NIa expression. Several of these plants were found to be resistant to PVY infection, inasmuch as they did not develop symptoms for at least 50 days (the duration of the experiments), and no viral accumulation could be detected in their leaves by ELISA. All of the descendents of resistant homozygous R2 plants were also resistant. Several of the plants transformed with the last three cistrons of PVY (bases 5812-9704; NIa-NIb-coat protein) were also resistant to PVY. None of the transformed plants exhibited resistance to tobacco mosaic virus. Exposure of the plants to 35 degrees C for 48 hr prior to inoculation lowered, but did not abolish, resistance.

Base Sequence↗
PubMed1993

Expression of the "helper component" protein of potato virus Y (PVY) in E. coli: possible involvement of a third protease.

Transmission of potyviruses by aphids depends on the presence of a virus encoded helper-component protein (HC) that also exhibits protease activity. HC was expressed in E. coli from two types of clones: a full-length cDNA clone of PVY and two 5' end clones containing the first three cistrons (3.6-3.7 kbp). The clones derived from the 5' end of PVY expressed HC of the size of the mature component. Other proteins reacting with antibodies to HC were also observed, and their sizes corresponded with those of expected intermediates resulting from partial protease cleavage of the three-cistron polyprotein. On the other hand, the only detectable HC-related product of the full-length clone was a mature-size HC. The presence of a third PVY protease among the first three cistrons is therefore suggested.

Cloning, Molecular↗
PubMed1993

Expression and assembly of the potato virus Y (PVY) coat protein (CP) in Escherichia coli cells.

A clone harboring the full-length cDNA of potato virus Y in a lambda-DASH vector under the control of a T7 promoter was introduced into Escherichia coli carrying the T7-RNA-polymerase gene on a plasmid. The viral coat protein was expressed and the product was of the same size as the corresponding mature protein in infected plants. Immunoelectronmicroscopy of transfected cell extracts revealed virus-like particles, indicating that the proteins involved in its processing and the viral coat protein retained their native activity.

Capsid↗
PubMed1993

Translational regulation of human beta interferon mRNA: association of the 3' AU-rich sequence with the poly(A) tail reduces translation efficiency in vitro.

The 3' AU-rich region of human beta-1 interferon (hu-IFN beta) mRNA was found to act as a translational inhibitory element. The translational regulation of this 3' AU-rich sequence and the effect of its association with the poly(A) tail were studied in cell-free rabbit reticulocyte lysate. A poly(A)-rich hu-IFN beta mRNA (110 A residues) served as an inefficient template for protein synthesis. However, translational efficiency was considerably improved when the poly(A) tract was shortened (11 A residues) or when the 3' AU-rich sequence was deleted, indicating that interaction between these two regions was responsible for the reduced translation of the poly(A)-rich hu-IFN beta mRNA. Differences in translational efficiency of the various hu-IFN beta mRNAs correlated well with their polysomal distribution. The poly(A)-rich hu-IFN beta mRNA failed to form large polysomes, while its counterpart bearing a short poly(A) tail was recruited more efficiently into large polysomes. The AU-rich sequence-binding activity was reduced when the RNA probe contained both the 3' AU-rich sequence and long poly(A) tail, supporting a physical association between these two regions. Further evidence for this interaction was achieved by RNase H protection assay. We suggest that the 3' AU-rich sequence may regulate the translation of hu-IFN beta mRNA by interacting with the poly(A) tail.

Animals↗
PubMed1992

Expression of active human interferon-beta in transgenic plants.

Tobacco plants were transformed with the human gene for interferon-beta (IFN-beta). Transformation was determined by the polymerase chain reaction (PCR), and expression was determined by Western blot analysis, by purifying the IFN from the transgenic plants, and by bioassays indicating its activity in human cells. Plants expressing IFN-beta were self-pollinated. IFN-beta-expressing progeny plants were selected and produced active IFN-beta, indicating stable transformation.

Base Sequence↗
PubMed1990

Cloning and mapping of the potato virus Y genome and its in vitro expression.

Full-length cDNA of genomic RNA of potato virus Y (PVY) was cloned in one piece into a lambda vector. The order of the EcoRI and SalI fragments of the inserted cDNA was determined. This is the first report of the cloning of a long, expressible, potyvirus genome. The availability of such a clone is a prerequisite for any further study of the molecular biology of this group of viruses, as they are expressed into a self-processed primary polyprotein.

Amino Acid Sequence↗
PubMed1990

Induction of an ATP-polymerizing enzyme in TMV-infected tobacco and its homology to the human 2'-5' A synthetase.

Several reports have indicated that tobacco carries an enzyme (APE) that, in the presence of poly (rI):(rC), polymerizes ATP to oligoadenylates. This paper demonstrates that the tobacco APE system comprises several proteins (estimated sizes: 32, 42, 67, and 84 +/- 10% kD). Only one of these proteins (the "67-kD" form) binds to poly (rI):(rC). This APE form has been purified by affinity chromatography on a synthetic ds-RNA column. Four tobacco proteins, including the purified one, crossreact with antibodies against the human enzyme, 2'-5' A synthetase. The ATP-binding capacity of some of these proteins has also been demonstrated. The amount of plant oligoadenylates obtained by polymerizing ATP with the purified APE form allows, for the first time, their direct analysis by TLC. The TLC analysis indicated that the oligomer produced by APE is not identical to the 2'-5' oligoadenylate. The appearance of the 2'-5' A-related proteins correlates with the build up of TMV infection, and the pattern of their stimulation and turnover was established. Nucleic acid hybridization indicates homology of tobacco DNA and RNA sequences with cloned cDNA of the human 2'-5' A synthetase gene. The stimulation in tobacco, upon TMV infection, of mRNA species homologous to the above human cDNA has been demonstrated. The analogy between the plant and the human system is discussed.

Adenine Nucleotides↗
PubMed1990

Two antiviral proteins from tobacco: purification and characterization by monoclonal antibodies to human beta-interferon.

Polyclonal antibodies to human beta-interferon reacted specifically with two plant proteins (gp22 and gp35) by Western blot analysis of crude protein extracts from tobacco leaves infected with tobacco mosaic virus. Immunoaffinity chromatography of these extracts on a column of immobilized monoclonal antibodies to human beta-interferon and then reversed-phase HPLC yielded gp22 and gp35 in a pure state. Both proteins reacted with the Schiff reagent and concanavalin A (indicating their glycoprotein nature) and exhibited antiviral activity (inhibiting tobacco mosaic virus replication in tobacco-leaf discs at concentrations of ng/ml). Each protein was cleaved by cyanogen bromide and the resultant peptides, separated by HPLC, were sequenced as far as the Edman degradation allowed, giving a total of 61 amino acid residues for gp22 and 105 residues for gp35, which represent 30-50% of their expected length. Computer analyses of the sequenced segments revealed no significant homology to human beta-interferon, each other, or any other recorded sequence.

Amino Acid Sequence↗