Rapaport L R, Mackie G A
Department of Biochemistry, University of Western Ontario, London, Canada.
J Bacteriol. 1994 Feb;176(4):992-8. doi: 10.1128/jb.176.4.992-998.1994.
A set of plasmids was constructed so as to contain point mutations which limit the efficiency and/or extent of translation of the gene for ribosomal protein S20. These plasmids were transformed into strains carrying mutations in the genes for polynucleotide phosphorylase (pnp-7), RNase E (rne-1), or both. Subsequently, the effect of translational efficiency on mRNA abundance and chemical half-life was determined. The data indicated that mutations altering translational efficiency also affected mRNA levels over a 10-fold range. This variation in mRNA abundance occurred independently of mutations in either RNase E or polynucleotide phosphorylase, both of which determine the stability of the S20 mRNAs. Moreover, a mutation at codon 15 which caused premature termination of translation of the S20 mRNA did not significantly reduce its stability in different genetic backgrounds. We propose a model in which initiation of translation competes for early steps in mRNA turnover, which could be the binding of RNase E itself or as a complex to one or more sites near the 5' terminus of the S20 mRNA.
构建了一组质粒，使其包含点突变，这些点突变会限制核糖体蛋白S20基因的翻译效率和/或程度。将这些质粒转化到携带多核苷酸磷酸化酶（pnp - 7）基因、核糖核酸酶E（rne - 1）基因或两者基因发生突变的菌株中。随后，测定了翻译效率对mRNA丰度和化学半衰期的影响。数据表明，改变翻译效率的突变在10倍范围内也会影响mRNA水平。mRNA丰度的这种变化独立于核糖核酸酶E或多核苷酸磷酸化酶的突变而发生，这两种酶都决定了S20 mRNA的稳定性。此外，导致S20 mRNA翻译提前终止的第15位密码子突变在不同遗传背景下并未显著降低其稳定性。我们提出了一个模型，其中翻译起始与mRNA周转的早期步骤竞争，这可能是核糖核酸酶E本身或作为复合物与S20 mRNA 5'末端附近的一个或多个位点结合。
