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Biomedical subjects

G Huez

Publications and source records attributed to G Huez.

At least 55 records · Page 3Linked to original sources
PubMed1984

Increased stability and antiviral activity of 2'-O-phosphoglyceryl derivatives of (2'-5')oligo(adenylate).

Metabolically stable analogues of (2'-5')oligo(adenylate), (2'-5')(A)n, might constitute a new class of antiviral agents as they mimic some of the effects of interferons. 2'-O-phosphoglyceryl derivatives of (2'-5')(A)n oligomers, (2'-5')(A)n-PGro have been synthesized by chemical modification of their terminal ribose residue. Such analogues are resistant to degradation by phosphodiesterases but remain sensitive to phosphatase activity, at least in cell-free extracts. In line with its increased stability, (2'-5')(A)n-PGro has a powerful antiviral activity against an RNA virus when microinjected with micropipettes into the cytoplasm of intact cells. This antiviral activity remains transient however, possibly as a consequence of degradation in intact cells. Since (2'-5')(A)n and its derivatives do not easily cross cell membranes, their possible use in antiviral chemotherapy is tightly linked with the development of vectors suitable for their administration in vivo.

Adenine Nucleotides↗
PubMed1984

Isolation and biological characterization of mouse LM fibroblast variants resistant to the cytotoxicity of polyriboinosinic polyribocytidylic acid after interferon treatment.

Mouse LM fibroblasts growing continuously in the absence of serum have an increased sensitivity to the cytotoxicity of poly(rI) X poly(rC) after interferon (IFN) exposure. This has allowed the isolation by an enrichment procedure of several independent and stable variant clones (IFN + I X C)R which are resistant to such a treatment. One of the resistant variants has been more extensively characterized as far as IFN action and IFN production are concerned. It behaves identically to the wild-type parent except for the spontaneous release of low amounts of IFN. The target of the mutation probably resides in a late step in the development of the cytotoxic response as revealed by microinjection techniques. The (IFN + I X C)R variants characterized here thus appear different from mutants in the IFN system isolated so far.

Animals↗
PubMed1984

Different bovine leukemia virus-induced tumors harbor the provirus in different chromosomes.

DNAs from 25 independent hamster X bovine somatic cell hybrids were submitted to the Southern blot analysis with probes made of unique cellular fragments adjacent to single-copy proviruses from three different bovine tumors. It appeared that these cellular sequences, and thus the respective proviruses, belonged to three different chromosomes in the three different tumors examined.

Animals↗
PubMed1983

Translational stability of plant viral RNAs microinjected into living cells. Influence of a 3'-poly(A) segment.

Three different alternative structural features have been shown to be present at the 3' terminus of plant viral RNAs: (a) a poly(A) track, (b) a tRNA-like structure, (c) no special structural or sequence characteristic. We have compared the translational stability after injection into frog oocytes of a representative of each type: (a) the small genomic RNA (M-RNA) of cowpea mosaic virus (CPMV), (b) the subgenomic mRNA for coat protein (RNA 4) of brome mosaic virus (BMV), (c) the subgenomic mRNA for coat protein (RNA 4) of alfalfa mosaic virus (AIMV). It has been shown that CPMV M-RNA exhibits the highest translational stability. However, the stability of AIMV RNA 4 is remarkably high and moreover significantly higher than that of BMV RNA 4. We demonstrate that, for all three viral RNA species considered, the presence of a poly(A) segment at the 3' end of the molecules improves the translational stability. From a comparative investigation in which AIMV RNA 4 was also injected into HeLa cells, it is concluded that the stability of a given non-adenylylated mRNA depends on the nature of the cytoplastic environment.

Animals↗
PubMed1983

Microinjected interferon does not promote an antiviral response in Hela cells.

Human fibroblast interferon (Hu IFN beta) was directly introduced with glass micropipets into the cytoplasm of Hela cells. Such an injection of more than 10(4) molecules per cell failed to induce any antiviral state when challenged with vesicular stomatitis virus (VSV). These findings are discussed in relation to the possible role of internalization in the mechanism of antiviral action of interferon.

HeLa Cells↗
PubMed1981

Usage of the three termination codons in a single eukaryotic cell, the Xenopus laevis oocyte.

Oocytes from Xenopus laevis were injected with purified amber (UAG), ochre (UAA), and opal (UGA) suppressor tRNAs from yeasts. The radioactively labeled proteins translated from the endogenous mRNAs were then separated on two-dimensional gels. All three termination codons are used in a single cell, the Xenopus laevis oocyte. But a surprisingly low number of readthrough polypeptides were observed from the 600 mRNAs studied in comparison to uninjected oocytes. The experimental data are compared with the conclusions obtained from the compilation of all available termination sequences on eukaryotic and prokaryotic mRNAs. This comparison indicates that the apparent resistance of natural termination codons against readthrough, as observed by the microinjection experiments, cannot be explained by tandem or very close second stop codons. Instead it suggests that specific context sequences around the termination codons may play a role in the efficiency of translation termination.

Animals↗
PubMed1981

Effect of tRNA pool balance on rate and uniformity of elongation during translation of fibroin mRNA in a reticulocyte cell-free system.

Unsuccessful attempts to synthesize complete fibroin chains in vitro were previously made in heterologous cell-free system [3]. In the present work, we succeeded to obtain complete translation of purified fibroin mRNA in a rabbit reticulocyte lysate. Whilst this work was being completed [1], similar results were published by Lizardi et al. [4]. The synthesis of full-sized molecules of fibroin (M.W. 360,000) was achieved by adding tRNA from the posterior silk gland to the cell-free system. With tRNA from other sources, both the translation rate and the amount of complete fibroin chains dropped. This effect of tRNA is situated at the elongation levels. Analysis of cell-free synthesized products by polyacrylamide gel electrophoresis shows that smaller discrete polypeptides are accumulated after 120 minutes of incubation. These polypeptides correspond to growing fibroin chains. This pattern of translation products suggests that elongation might decelerate at specific sites of the fibroin mRNA. These results show that a tRNA pool adjusted to mRNA codon frequency is required to obtain the maximal average elongation rate. A stochastic model based on random acceptance of tRNA at the ribosomal A site for the codon-anticodon recognition process can explain this phenomenon. It can also explain the occurrence of the unfinished discrete fibroin polypeptides during in vitro translation.

Animals↗
PubMed1981

Translational stability of native and deadenylylated rabbit globin mRNA injected into HeLa cells.

HeLa human cells were injected with a natural mixture of rabbit alpha and beta globin mRNA. They were incubated for 6 hr with [35S]methionine either immediately after injection or 20 hr later. The labeled proteins in the injected cells were analyzed by fluorography of two-dimensional electrophoresis gels. By using this procedure, it was possible to show that, during the first few hours after injection, both alpha and beta globin molecules are synthesized with an alpha to beta ratio approximately equal to 0.6. The rate of synthesis of alpha globin decreased significantly faster than that of beta globin over a 26-hr period after injection of the two mRNAs. It thus seems that two messenger RNAs coding for closely related polypeptides possess a markedly different translational stability. When deadenylylated rabbit globin mRNAs were injected into HeLa cells, no globin synthesis could be detected by the techniques used. We conclude that the translational half-life of mRNAs lacking poly(A) is very short in these cells. It is thus clear that the poly(A) segment is required to ensure stability to globin mRNA in somatic cells as in Xenopus oocytes.

Adenine↗
PubMed1981

[tRNA adaptation and the optimization of translation].

The intracellular level of each tRNA species is adjusted to the codon frequency of the mRNA being decoded. This was first observed in such highly differentiated cells as the silk gland of Bombyx mori, which produces fibroin and sericin, and the rabbit reticulocyte. tRNA adaptation also occurs in other cell types from E. coli to mammalian cells. Regardless of the mechanism regulating tRNA biosynthesis, we believe that tRNA adaptation is the basic step optimizing chain elongation at the ribosomal level. We propose the system of trial and error as a working model for the ribosome. This model clarifies the correlations between iso-accepting tRNA levels and codon frequencies, as well as the effect of tRNA pool balance on mean elongation rate and non-uniform individual elongation rate (depending on whether codons are rare or abundant) for fibroin mRNA translated in a reticulocyte cell-free system.

Adaptation, Physiological↗
PubMed1978

Synthesis of carp proinsulin in Xenopus oocytes.

Total poly(A)-containing RNA from Brockmann boides of carp (Cyprinus carpio) directs the synthesis of authentic carp proinsulin in Xenopus oocytes. Neither preproinsulin nor further processing of the proinsulin to insulin can be detected in the oocytes.

Animals↗
PubMed1977

Frog oocytes synthesize and completely process the precursor polypeptide to virion structural proteins after microinjection of avian myeloblastosis virus RNA.

After microinjection of Xenopus laevis oocytes with RNA from avian myeloblastosis virus, viral structural proteins p27, p19, p15, and p12 are formed by a sequence of posttranslational cleavages of a high-molecular-weight precursor polypeptide. The 60-70S RNA aggregate or its 30-40S RNA subunits obtained by heat or formamide treatment possess the same ability to serve as template in X. laevis oocytes. The processing pattern of virus-specific precursor polypeptides is the same in X. laevis oocytes as in chick embryo fibroblasts infected with avian myeloblastosis virus, but the processing takes place at a much slower rate.

Animals↗