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PubMed1969

[Further anatomical observations on the site and form of several viscera. The anatomical works of Winslow collected from the records of the Royal academy of Sciences of Paris translated from the French, with a dissertation of the above-mentioned author on the uncertainty of the signs of death, and five tables from Drake's Anthropology, with their explanation translated from the English. In Bologna, 1720. By Bartholomeo Borhi degli Orefici, with permission of the authorities].

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Anatomy↗
PubMed1984

Heat shock-induced translational alterations in HeLa cells. Initiation factor modifications and the inhibition of translation.

Heat shock at 45 degrees C virtually abolishes protein synthesis in HeLa cells, but return to 37 degrees C effects a complete recovery and the concomitant synthesis of heat shock-induced proteins. Heat shock induces polysome disaggregation, indicating initiation is principally inhibited. In vitro assays for initiation factor activities reveal heat shock inhibits eukaryotic initiation factor 2 (eIF-2), eIF-(3 + 4F), and eIF-4B. Immunoblot analyses show that eIF-2 alpha and eIF-2 beta become modified during heat shock, and eIF-4B variants disappear. Upon return to 37 degrees C, these alterations reverse. The modifications of eIF-2 alpha and eIF-4B are due to phosphorylation and dephosphorylation, respectively. Enzymatic activities induced by heat shock inhibit protein synthesis and modify initiation factors in a rabbit reticulocyte lysate. Initiation factor modifications may contribute to, or cause, protein synthesis inhibition.

Centrifugation, Density Gradient↗
PubMed2005

Differences in codon bias cannot explain differences in translational power among microbes.

BACKGROUND: Translational power is the cellular rate of protein synthesis normalized to the biomass invested in translational machinery. Published data suggest a previously unrecognized pattern: translational power is higher among rapidly growing microbes, and lower among slowly growing microbes. One factor known to affect translational power is biased use of synonymous codons. The correlation within an organism between expression level and degree of codon bias among genes of Escherichia coli and other bacteria capable of rapid growth is commonly attributed to selection for high translational power. Conversely, the absence of such a correlation in some slowly growing microbes has been interpreted as the absence of selection for translational power. Because codon bias caused by translational selection varies between rapidly growing and slowly growing microbes, we investigated whether observed differences in translational power among microbes could be explained entirely by differences in the degree of codon bias. Although the data are not available to estimate the effect of codon bias in other species, we developed an empirically-based mathematical model to compare the translation rate of E. coli to the translation rate of a hypothetical strain which differs from E. coli only by lacking codon bias. RESULTS: Our reanalysis of data from the scientific literature suggests that translational power can differ by a factor of 5 or more between E. coli and slowly growing microbial species. Using empirical codon-specific in vivo translation rates for 29 codons, and several scenarios for extrapolating from these data to estimates over all codons, we find that codon bias cannot account for more than a doubling of the translation rate in E. coli, even with unrealistic simplifying assumptions that exaggerate the effect of codon bias. With more realistic assumptions, our best estimate is that codon bias accelerates translation in E. coli by no more than 60% in comparison to microbes with very little codon bias. CONCLUSIONS: While codon bias confers a substantial benefit of faster translation and hence greater translational power, the magnitude of this effect is insufficient to explain observed differences in translational power among bacterial and archaeal species, particularly the differences between slowly growing and rapidly growing species. Hence, large differences in translational power suggest that the translational apparatus itself differs among microbes in ways that influence translational performance.

Bacterial Physiological Phenomena↗
PubMed1990

Cell-free translation systems prepared from starfish oocytes faithfully reflect in vivo activity; mRNA and initiation factors stimulate supernatants from immature oocytes.

Meiotic maturation stimulates a change in the translation of stored mRNAs: mRNAs encoding proteins needed for growth of oocytes are translated before meiotic maturation, whereas those encoding proteins required for cleavage are translated after meiotic maturation. Studies of translational regulation during meiotic maturation have been limited by the lack of translationally active cell-free supernatants. Starfish oocytes are ideal for preparing cell-free translation systems because experimental application of the hormone 1-methyladenine induces their maturation, synchronizing meiosis. We have prepared such systems from both immature and mature oocytes of starfish. Changes in protein synthesis rates and the specificity of proteins synthesized in these cell-free translation supernatants mimic those seen in vivo. Supernatants both from immature and mature oocytes have a high capacity to initiate new translation because 90% of the proteins made are newly initiated from mRNAs. Cell-free supernatants from mature oocytes have a much higher rate of initiation of translation than those from immature oocytes and use the 43S preinitiation complexes more efficiently in initiation of translation. Similarly, we have shown that mRNAs and initiation factors are rate limiting in cell-free translation systems prepared from immature oocytes. In addition, cell-free translation systems prepared from immature oocytes are only slightly, if at all, inhibitory to cell-free translation systems from mature oocytes. Thus, soluble inhibitors, if they exist, are rapidly converted by cell-free supernatants from mature oocytes. The similarities between translation in our starfish cell-free translation systems and in intact oocytes suggests that the cell-free translation systems will be useful tools for further studies of maturation events and translational control during meiosis.

Animals↗
PubMed1994

Cap-dependent and cap-independent translation by internal initiation of mRNAs in cell extracts prepared from Saccharomyces cerevisiae.

Translation extracts were prepared from various strains of Saccharomyces cerevisiae. The translation of mRNA molecules in these extracts were cooperatively enhanced by the presence of 5'-terminal cap structures and 3'-terminal poly(A) sequences. These cooperative effects could not be observed in other translation systems such as those prepared from rabbit reticulocytes, wheat germ, and human HeLa cells. Because the yeast translation system mimicked the effects of the cap structure and poly(A) tail on translational efficiency seen in vivo, this system was used to study cap-dependent and cap-independent translation of viral and cellular mRNA molecules. Both the 5' noncoding regions of hepatitis C virus and those of coxsackievirus B1 conferred cap-independent translation to a reporter coding region during translation in the yeast extracts; thus, the yeast translational apparatus is capable of initiating cap-independent translation. Although the translation of most yeast mRNAs was cap dependent, the unusually long 5' noncoding regions of mRNAs encoding cellular transcription factors TFIID and HAP4 were shown to mediate cap-independent translation in these extracts. Furthermore, both TFIID and HAP4 5' noncoding regions mediated translation of a second cistron when placed into the intercistronic spacer region of a dicistronic mRNA, indicating that these leader sequences can initiate translation by an internal ribosome binding mechanism in this in vitro translation system. This finding raises the possibility that an internal translation initiation mechanism exists in yeast cells for regulated translation of endogenous mRNAs.

Animals↗
PubMed2004

Preparing the next generation of scientists in translation research.

AIM: Four questions about translation research are considered in this article. (1) Why should there be concern about preparing nurse scientists for translation research? (2) Are current research-intensive doctoral programs in nursing preparing graduates for translation research? (3) Should targeted efforts be made to systematically prepare nurses in translation research? (4) What strategies would be useful? QUESTION 1: It is argued that translation research is needed in order to increase the odds that interventions found to be efficacious can be effectively translated into practices that will produce desired outcomes. Thus, evidence from translation research is a very important component of the science base needed to guide innovation in practice. Another reason of concern in preparing translation researchers is the growing pace of research into the efficacy of interventions, which accelerates the need for translation research. Furthermore, the emergence of clinical doctoral programs in nursing that will be seeking faculty with expertise in translation research supports the need for preparing scientists in translation research. QUESTION 2: To determine whether translation research was visible in current research-intensive doctoral programs, a Web-based review of these programs offered by colleges and universities in the database of the American Association of Colleges of Nursing (AACN) was conducted in the fall of 2003. The search revealed that in the 79 programs surveyed, no school identified an area of emphasis in terms that suggested a component of translation science such as research dissemination or utilization, knowledge transfer, diffusion of innovation, or technology transfer. Less than a dozen courses could be located that focused on topics related to translation research or translation science. QUESTIONS 3 AND 4: The case is made that more attention should be given to preparing translation scientists in research-intensive doctoral programs in nursing, and several strategies were suggested for moving toward that goal.

Curriculum↗
PubMed2006

Cap-dependent and hepatitis C virus internal ribosome entry site-mediated translation are modulated by phosphorylation of eIF2alpha under oxidative stress.

Chronic hepatitis C is often associated with oxidative stress. Hepatitis C virus (HCV) utilizes an internal ribosome entry site (IRES) element for translation, in contrast to cap-dependent translation of the majority of cellular proteins. To understand how virus translation is modulated under oxidative stress, HCV IRES-mediated translation was compared with cap-dependent translation using a bicistronic reporter construct and hydrogen peroxide (H2O2) as a stress inducer. In H2O2-sensitive HeLa cells, H2O2 repressed translation in a time- and dose-dependent manner, concomitant with the kinetics of eIF2alpha phosphorylation. A phosphomimetic of eIF2alpha, which mimics the structure of the phosphorylated eIF2alpha, was sufficient to repress translation in the absence of H2O2. In H2O2-resistant HepG2 cells, H2O2 activated both HCV IRES-mediated and cap-dependent translation, associated with an increased level of phospho-eIF2alpha. It was postulated that H2O2 might stimulate translation in HepG2 cells via an eIF2alpha-independent mechanism, whereas the simultaneous phosphorylation of eIF2alpha repressed part of the translational activities. Indeed, the translational repression was released in the presence of a non-phosphorylatable mutant, eIF2alpha-SA, resulting in further enhancement of both translational activities after exposure to H2O2. In HuH7 cells, which exhibited an intermediate level of sensitivity towards H2O2, both HCV IRES-mediated and cap-dependent translational activities were upregulated after treatment with various doses of H2O2, but the highest level of induction was achieved with a low level of H2O2, which may represent the physiological level of H2O2. At this level, the HCV IRES-mediated translation was preferentially upregulated compared with cap-dependent translation.

Cell Line↗
PubMed1995

m7GpppG cap dependence for efficient translation of Drosophila 70-kDa heat-shock-protein (Hsp70) mRNA.

To investigate whether preferential translation of the heat-shock mRNAs occurs via cap-independent translation, the requirement for the m7GpppG cap structure for efficient translation of 70-kDa heat-shock-protein (Hsp70) mRNA was quantified by in vitro translation and by in vivo translation following electroporation. Hsp70 mRNA was transcribed in vitro with and without a cap structure. Translation in the rabbit reticulocyte or wheat germ lysate was reduced about 70% when the cap was absent. For comparison, translation of uncapped encephalomyocarditis virus 5'-untranslated-region-containing mRNA was equal to or greater than capped mRNA, whereas translation of several non-heat-shock mRNAs was reduced by 85-95% when capping was omitted. Cap-dependent translational stimulation of Hsp70 is not due to increased stability, is not a kinetic effect, and requires the methylated GpppG. To confirm the in vitro analyses, capped and uncapped mRNA were introduced into Drosophila tissue culture cells by electroporation, followed by heat shock. Paralleling the in vitro results, uncapped Hsp70 mRNA translation was 70-80% reduced relative to the capped form. Complementary experiments in which eIF-4 was inactivated in vitro using either m7GTP cap analogue or foot-and-mouth-disease virus L protease expression likewise indicated that the cap-dependent translation pathway is required for optimal Hsp mRNA translation. Since cellular Hsp70 mRNA translation during heat shock is very efficient, it is unlikely that translation via a cap-independent pathway is the principal basis for preferential translation.

Animals↗