Guillerez J, Gazeau M, Dreyfus M
Laboratoire de Génétique Moléculaire (CNRS D1302), Ecole Normale Supérieure, Paris, France.
Nucleic Acids Res. 1991 Dec 25;19(24):6743-50. doi: 10.1093/nar/19.24.6743.
We have constructed a series of 44 Escherichia coli strains in which the chromosomal region corresponding to the Ribosome Binding Site (RBS) of the lacZ gene, has been replaced by small DNA fragments harboring either RBSs from other genes, or artificial RBSs. The beta-galactosidase expression from these strains ranges from 1 to 130 per cent of that of the parental strain. Using this collection, we demonstrate here that strain-to-strain variations in expression are paralleled by nearly equivalent variations in lacZ mRNA content. We propose that, in this system, polarity and mRNA stability are tightly coupled to translation initiation, so that changes in RBS efficiency are detected mainly as changes in mRNA concentration rather than in the spacing between translating ribosomes. In addition, we show that the mRNA sequence immediately downstream from the initiator codon influences per se the lifetime of the lacZ mRNA. We discuss the mechanism of the interdependence between translation, transcription and degradation in this gene, and speculate about the general role of this interdependence in determining the expression of bacterial genes.
我们构建了一系列44株大肠杆菌菌株，其中与lacZ基因核糖体结合位点（RBS）相对应的染色体区域已被携带其他基因的RBS或人工RBS的小DNA片段所取代。这些菌株的β-半乳糖苷酶表达量为亲本菌株的1%至130%。利用这一菌株集合，我们在此证明，表达上的菌株间差异与lacZ mRNA含量的几乎同等变化并行。我们提出，在这个系统中，极性和mRNA稳定性与翻译起始紧密耦合，因此RBS效率的变化主要表现为mRNA浓度的变化，而不是翻译核糖体之间间距的变化。此外，我们表明起始密码子下游紧邻的mRNA序列本身会影响lacZ mRNA的寿命。我们讨论了该基因中翻译、转录和降解之间相互依存的机制，并推测了这种相互依存在决定细菌基因表达中的普遍作用。
