PubMed · 1367920
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W C Merrick. 1990. Gene expression using cell-free systems.. https://doi.org/10.1016/0958-1669(90)90014-c
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Large quantities of a catalytically active protein have been produced in a cell free system. More than 10(9) copies of protein were produced from each DNA plasmid containing DNAfol, the bacterial gene encoding dihydrofolate reductase (DHFR). The strategy employed, denoted gene amplification with transcription/translation (GATT), involves sequential coupling of (i) DNA amplification by the polymerase chain reaction (PCR) and (ii) in vitro RNA transcription by T7 RNA polymerase, followed by (iii) translation of the run-off transcripts in a rabbit reticulocyte system. The protein product had the expected size (18 kDa) and catalyzed the NADPH-dependent reduction of 7,8-dihydrofolic acid to 5,6,7,8-tetrahydrofolic acid as efficiently as authentic DHFR. Potential applications of the strategy include large scale production of enzymes containing synthetic amino acids and facilitation of the characterization of the function of genes encountered in genomic mapping studies.
Cell-free translation in reversed micelles (RM) of surfactants in organic solvents is demonstrated using as an example the synthesis of human interleukin-2 by the wheat germ translation system solubilized in Brij 96 (oleyl-poly(10)oxyethylene ether) RM in cyclohexane. The translation system components and the product were recovered from the RM system by acetone precipitation. The recovery and translation reaction yields depended on the degree of surfactant hydration. The translation yields in Brij 96 RM were close to that observed in regular aqueous solution. The Brij 96 RM system is regarded as a promising media for the cell-free synthesis of hydrophobic proteins. Meanwhile, no translation reaction was observed in Aerosol OT (sodium bis(2-ethylhexyl) sulfosuccinate) RM in octane, which presumably is due to the ability of Aerosol OT to bind Mg2+ ions necessary for the functioning of the translation apparatus.
The 5' ends of all human immunodeficiency virus type I (HIV-1) transcripts have the potential to coordinately regulate translation of HIV-1 mRNAs. Conflicting observations of the translational impact of these sequences in various systems stimulated these analyses of translation in reticulocyte lysates. We report a sensitive, rapid, quantitative, and inexpensive cell-free translation assay in which translational efficiency is monitored by enzymatic assay of the translation products. Using this assay and conventional radiolabeling assays, we demonstrate that the HIV-1 transcript leader inhibits downstream translation and that the stem-loop structure is required. Under our assay conditions, this inhibition occurs predominantly in cis and is not mediated by the 68 kD, interferon-induced, double-stranded RNA-activated kinase (p68). However, under other assay conditions the HIV-1 leader may activate p68 and inhibit translation in trans. We show that variation between individual preparations of cell-free extracts can dramatically alter the magnitude of the translational inhibition by the HIV-1 leader. Further, we provide evidence that a heat-labile factor is required for efficient translation of transcripts containing the HIV-1 leader. These observations provide a foundation for identifying factors required for translation of HIV-1 transcripts.