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P Linder

Publications and source records attributed to P Linder.

At least 19 recordsLinked to original sources
PubMed1992

ATP hydrolysis by initiation factor 4A is required for translation initiation in Saccharomyces cerevisiae.

Saccharomyces cerevisiae translation initiation factor eIF-4A, an RNA helicase of the Asp-Glu-Ala-Asp (DEAD) box protein family, was mutated in the putative ATP binding site and expressed in Escherichia coli. Mutant proteins with alanine at position 66 replaced by glycine [eIF-4A(A66G)] or valine [eIF-4A(A66V)] were purified from Escherichia coli extracts and analyzed in vitro for activity in ATP crosslinking, ATP hydrolysis, RNA helicase, and translation assays. The results show that in vitro ATP hydrolysis activity, RNA helicase activity, and translation activity of eIF-4A correlate with in vivo activity of the factor. Whereas eIF-4A(A66G) showed wild-type activity in all assays, eIF-4A(A66V) was active in ATP crosslinking but inactive in ATP hydrolysis and RNA helicase assays. In vitro translation was supported by wild-type eIF-4A and eIF-4A(A66G) but not by eIF-4A(A66V). The results show that, for their translation, the majority of mRNAs from Saccharomyces cerevisiae including an mRNA with the initiator AUG positioned 8 nucleotides downstream of the cap structure require eIF-4A that is able to hydrolyze ATP.

Adenosine Triphosphate↗
PubMed1992

Molecular biology of translation in yeast.

The combination of genetic, molecular and biochemical approaches have made the yeast Saccharomyces cerevisiae a convenient organism to study translation. The sequence similarity of translation factors from yeast and other organisms suggests a high degree of conservation in the translational machineries. This view is also strengthened by a functional analogy of some proteins implicated in translation. Beautiful genetic experiments have confirmed existing models and added new insights in the mechanism of translation. This review summarizes recent experiments using yeast as a model system for the analysis of this complex process.

Base Sequence↗
PubMed1992

D-E-A-D protein family of putative RNA helicases.

RNA metabolism plays a central role in cell growth. It is essential to regulate RNA synthesis, processing, stability and degradation. Conformational changes in RNA are key elements in regulating cellular processes. Recently, an increasing number of putative RNA helicases from different organisms ranging from Escherichia coli to humans and viruses have been identified. They are involved in diverse cellular functions such as RNA splicing, ribosome assembly, initiation of translation, spermatogenesis, embryogenesis, and cell growth and division. Based on sequence homologies these proteins were grouped in a family, the D-E-A-D box protein family (D-E-A-D = Asp-Glu-Ala-Asp). Some of the better characterized members have been shown to possess ATP-binding and hydrolysing activities as well as ATP-dependent RNA helicase activities. Most of the genes encoding such proteins have been isolated from yeast, on which we will focus in this review. From sequence data, three of the members form a subfamily, the D-E-A-H subfamily.

Amino Acid Sequence↗
PubMed1992

Psychomotor recovery following propofol or isoflurane anaesthesia for day-care surgery.

A newly developed test for the assessment of psychomotor recovery--the perceptive accuracy test (PAT)--is described. Seventy-four subjects who performed the test though that it was easy to perform and some were motivated to try it on a number of occasions. Eight persons performed the test on different days and at different periods of time; the results were consistent and reproducible. Eight more persons were then asked to do the test 4 times at 15-min intervals; no 'learning' was seen with this test. A randomized, prospective study was then performed in two groups of 15 patients, undergoing arthroscopic procedures of the knee. Anaesthesia was induced with propofol and maintained with an infusion of propofol 12 mg/kg/h for the first 15 min, followed by 8 mg/kg/h subsequently in the propofol group. In the isoflurane group, anaesthesia was also induced with propofol, but isoflurane (0.5-2%) was used to maintain anaesthesia. Alfentanil was the analgesic used in both groups of patients. Results were compared with a third group of unanaesthetised controls, who were asked to perform psychomotor tests including choice reaction time and PAT at 30-min intervals for 2.5 h. There was a significant difference (P less than 0.01) in psychomotor recovery on the PAT-200 between the propofol group and control groups, but not in the isoflurane and control groups at 30 min. Both groups had returned to baseline values at 60 min in the PAT-60 and PAT-200. The choice reaction time showed no significant difference in either group 30 min after the anaesthetic.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

A copy-number mutant of plasmid pSC101.

Copy-number mutants of plasmid pSC101 were isolated by u.v. mutagenesis and selection for elevated expression of ampicillin resistance. Three independent mutations were identical and mapped in codon 93 of the initiation protein RepA. The mutated plasmids were maintained at a level four to five times higher than that of the wild type. For one of them, it was determined that: (i) the mRNA of the autoregulated repA gene, cloned onto a pUC19 plasmid under the control of its own promoter, was expressed at a level 1.7 times higher than that of the wild type; (ii) the RepA protein, under the same conditions, was expressed at a similarly higher level; (iii) the affinity of the mutated protein for three repeated sequences in the origin region of the plasmid was, on average, 3.4 times higher than that of the wild-type protein. We postulate that the copy-number effect is due to a combination of these two effects, i.e. higher protein concentration and increased affinity of the protein for the repeated sequences.

Ampicillin Resistance↗
PubMed1991

Translation initiation factor 4A from Saccharomyces cerevisiae: analysis of residues conserved in the D-E-A-D family of RNA helicases.

The eukaryotic translation initiation factor 4A (eIF-4A) possesses an in vitro helicase activity that allows the unwinding of double-stranded RNA. This activity is dependent on ATP hydrolysis and the presence of another translation initiation factor, eIF-4B. These two initiation factors are thought to unwind mRNA secondary structures in preparation for ribosome binding and initiation of translation. To further characterize the function of eIF-4A in cellular translation and its interaction with other elements of the translation machinery, we have isolated mutations in the TIF1 and TIF2 genes encoding eIF-4A in Saccharomyces cerevisiae. We show that three highly conserved domains of the D-E-A-D protein family, encoding eIF-4A and other RNA helicases, are essential for protein function. Only in rare cases could we make a conservative substitution without affecting cell growth. The mutants show a clear correlation between their growth and in vivo translation rates. One mutation that results in a temperature-sensitive phenotype reveals an immediate decrease in translation activity following a shift to the nonpermissive temperature. These in vivo results confirm previous in vitro data demonstrating an absolute dependence of translation on the TIF1 and TIF2 gene products.

Amino Acid Sequence↗
PubMed1991

[Facial injuries in bicyclists: epidemiological analysis and prophylactic consequences].

Bicycle accidents in adults are common and concern frequently injuries to head and face. 150 of totally 216 patients with cycle accidents in a six month' prospective study at the Basel University Hospital showed face and head trauma. 85 severe facial injuries treated operatively by the Clinic for Reconstructive Surgery between 1985 and 1989 are analysed in detail. These facial injuries are rarely life threatening and normally the postoperative outcome is good. Nevertheless, usual bicycle helmets cannot avoid facial trauma. Therefore traffic educational programs are the most important prophylactic efforts. Technical progress and improvement of the bicycles ask for better trained cyclists. Further more, the importance of really respecting the traffic rules as well as the construction of separate cycle routes is stressed.

Accidents, Traffic↗
PubMed1990

The ADE2 gene from Saccharomyces cerevisiae: sequence and new vectors.

We have determined the sequence of a DNA fragment encoding the ADE2 gene from Saccharomyces cerevisiae. A DNA fragment of 2241 bp capable of complementing ade2 mutations was modified so it is available as a single BglII fragment for use in yeast vectors or for gene disruptions. The minimal fragment codes for a putative protein which is highly similar to the protein encoded by the ADE6 gene from Schizosaccharomyces pombe and to the proteins encoded by the purEK operon of Escherichia coli.

Amino Acid Sequence↗
PubMed1990

Expression of translation initiation factor 4A from yeast and mouse in Saccharomyces cerevisiae.

The eukaryotic translation initiation factor 4A (eIF-4A) plays an important role in regulating initiation. To analyze its function in yeast, we carried out a mutational analysis of the TIF1 and TIF2 genes, which encode eIF-4A. Expression of these two yeast genes has also been investigated at the transcriptional level and it has been found that both are expressed in wild-type yeast cells. Analysis of the expression of eIF-4A-beta-galactosidase fusion proteins reveals that the TIF2 gene is more highly expressed than the TIF1 gene. Interestingly, the yeast eIF-4A protein shows a high degree of amino acid sequence similarity to the mouse homologue. However, we find that the mammalian factor does not support protein synthesis in yeast either in vivo or in vitro.

Animals↗
PubMed1990

Baker's yeast, the new work horse in protein synthesis studies: analyzing eukaryotic translation initiation.

The possibility of combining powerful genetic methods with biochemical analysis has made baker's yeast Saccharomyces cerevisiae the organism of choice to study the complex process of translation initiation in eukaryotes. Several new initiation factor genes and interactions between components of the translational machinery that were not predicted by current models have been revealed by genetic analysis of extragenic suppressors of translational initiation mutants. In addition, a yeast cell-free translation system has been developed that allows in vivo phenotypes to be correlated with in vitro biochemical activities. We summarize here the current view of yeast translational initiation obtained by these approaches.

Animals↗
PubMed1989

Translation in Saccharomyces cerevisiae: initiation factor 4A-dependent cell-free system.

Yeast Saccharomyces cerevisiae genes TIF1 and TIF2 (translation initiation factor) encode a protein tentatively called translation initiation factor (Tif) due to the similarity of its amino acid sequence and its molecular weight to mammalian eukaryotic initiation factor 4A. To clarify whether Tif is involved in translation, we produced an affinity-purified anti-Tif antibody by using Tif isolated from a Tif-overproducing yeast strain as immunogen and an Escherichia coli strain expressing Tif from an expression vector to provide the extract for affinity purification of the antibody. By using chromatographic procedures and the affinity-purified anti-Tif antibody as probe to identify Tif-containing fractions, we purified Tif from wild-type yeast cells. When yeast cells containing the only TIF1 gene on a plasmid under the control of the galactose-inducible CYC1-GAL10 promoter were grown in medium containing glucose as the carbon source, the production of Tif was shut off and growth was arrested. Lysates made from these cells were inactive in in vitro translation. Addition of Tif to these lysates restored in vitro protein synthesis. These results show that Tif is a translation factor, the yeast homologue of mammalian translation initiation factor 4A.

Blotting, Western↗
PubMed1989

An essential yeast protein, encoded by duplicated genes TIF1 and TIF2 and homologous to the mammalian translation initiation factor eIF-4A, can suppress a mitochondrial missense mutation.

We describe the isolation and characterization of two previously undescribed genes, TIF1 and TIF2, from Saccharomyces cerevisiae. The protein-encoding sequences of the two genes are highly conserved, resulting in two completely identical proteins, whereas the flanking regions show no obvious homology. The two yeast proteins are highly similar to the translation initiation factor eIF-4A from mouse. Elevated gene dosage of TIF1 or TIF2 results in the suppression of a missense mutation in the mitochondrial oxi2 gene, which codes for subunit III of cytochrome-c oxidase, although the sequence of the Tif protein indicates its cytoplasmic localization. Inactivation of either gene by gene disruption has no effect on cell viability or on mitochondrial functions. However, simultaneous inactivation of both genes is lethal to the cell.

Amino Acid Sequence↗
PubMed1989

[Spontaneous rupture of the extensor pollicis longus].

A review of the literature is followed by the analysis of a series of forty-four patients who were treated by extensor indicis transposition. Twenty-five patients could be reached for a clinical follow-up examination, nine further patients were interviewed by telephone; of the remaining ten patients, seven could not be reached and three had died. Excluded from the series were patients with rheumatoid arthritis. Results were evaluated according to the scheme suggested by Geldmacher and coworkers. According to their evaluation scheme, we can report fourteen excellent, eight good, three satisfactory, and no bad results. Subjectively, the results were even better, with twenty-eight patients reporting excellent, four good, and two satisfactory results, including those nine patients contacted by telephone only. Strength of extension of the index finger was not diminished after the extensor indicis transposition when all fingers were extended simultaneously. However, there was a deficit of extension in a few cases when the remaining fingers were clenched to a fist. This indicates that an alternative method should probably be recommended in patients with professions where individual extension of the index finger is of paramount importance. It is also suggested that additional functional tests, convertible into score points, might render the evaluation more realistic than measurements only. Inclusion of these additional functional tests might also give an explanation for the discrepancy between patients' subjective results and those as a result of measurement only.

Follow-Up Studies↗
PubMed1986

[Do pathologico-anatomic parameters modify the incidence of recurrence following conservative breast surgery and radiotherapy?].

201 breast cancer patients (pT1-2, pN0-1) were treated with conservative breast surgery and radiation therapy. 28 (13.9%) treatment failures, -13 (6.5%) local recurrences, 4 (2.0%) axillary - and 11 (5.5%) distant metastases -, were found overall after a mean follow-up of 47 months. The differences between pT2 and pT1-tumors (20.6% vs 10.5%) and nodal positive versus nodal negative patients (28.1% vs 6.8%) are statistically significant. No differences were seen regarding histological features.

Breast↗