Stability of β-Galactosidase Messenger Ribonucleic Acid in Escherichia coli

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Abstract
Ben-Hamida, Fakher (Washington University School of Medicine, St. Louis, Mo.), and David Schlessinger . Stability of β-galactosidase messenger ribonucleic acid in Escherichia coli . J. Bacteriol. 90: 1611–1616. 1965.—Synthesis of β-galactosidase stops within several minutes when preinduced, permeaseless cultures are diluted into medium containing 40 μg/ml of 5-fluorouracil (5-FU) but no inducer. However, if inducer (isopropylthiogalactoside) is left in the medium, enzyme formation in the presence of 5-FU continues for at least 11 min. Thus, inducer may increase the differential metabolic stability of the corresponding messenger ribonucleic acid (RNA; defined as the capacity to produce measurable enzyme) in inducible strains. However, such an interpretation requires that 5-FU rapidly arrest the further synthesis of messenger RNA competent to form active enzyme. C 14 -5-FU, like uracil, does appear to enter cells without measurable lag, saturating the pool of uracil nucleotides, and thereby the messenger RNA being formed, within several minutes. That 5-FU acts very quickly is also supported by the similar continuation of enzyme synthesis in the presence of inducer and antibiotics (actinomycin D and proflavine) which shut off all RNA synthesis, as well as by the response to 5-FU of enzyme synthesis in various constitutive mutants.