Sampson L L, Hendrix R W, Huang W M, Casjens S R
Department of Cellular, Viral and Molecular Biology, University of Utah Medical Center, Salt Lake City 84132.
Proc Natl Acad Sci U S A. 1988 Aug;85(15):5439-43. doi: 10.1073/pnas.85.15.5439.
The late operon of bacteriophage lambda contains the genes encoding the morphogenetic proteins of the phage. These genes are transcribed equally from the single late promoter. Although the functional half-lives of the mRNA for the various genes of this operon vary less than 2-fold, their relative rates of expression have been shown to vary by nearly 1000-fold. This variation could result from differing rates of translation initiation, from overlapping upstream translation, or from differential elongation rates due to the presence of codons for which the corresponding tRNAs are rare. To distinguish between these possibilities, we have cloned sequences surrounding the initiator codons of several of these genes and measured their ability to drive synthesis of hybrid lambda-beta-galactosidase proteins. The rates of expression of the hybrid genes thus produced correlate very well with the natural rates of expression of the corresponding phage genes, suggesting that the rate of initiation of translation controls the relative expression rates of these genes.
噬菌体λ的晚期操纵子包含编码噬菌体形态发生蛋白的基因。这些基因从单个晚期启动子等量转录。尽管该操纵子中各个基因的mRNA的功能半衰期变化不到2倍，但它们的相对表达速率已显示出相差近1000倍。这种差异可能是由于翻译起始速率不同、上游翻译重叠或由于存在相应tRNA稀少的密码子导致的延伸速率差异引起的。为了区分这些可能性，我们克隆了其中几个基因起始密码子周围的序列，并测量了它们驱动合成λ-β-半乳糖苷酶杂交蛋白的能力。由此产生的杂交基因的表达速率与相应噬菌体基因的天然表达速率非常吻合，这表明翻译起始速率控制着这些基因的相对表达速率。
