Peacock S, Cenatiempo Y, Robakis N, Brot N, Weissbach H
Proc Natl Acad Sci U S A. 1982 Aug;79(15):4609-12. doi: 10.1073/pnas.79.15.4609.
Plasmids pNF1337 and pNF1341, which contain part of the L10 operon including the RNA polymerase beta-subunit gene, have been used as templates in vitro to investigate expression of the beta-subunit gene. For these studies, the synthesis of the first dipeptide of the beta subunit, fMet-Val, was measured instead of that of the entire protein. By using this dipeptide system, we studied the effects of RNA polymerase holoenzyme and L factor (nus A gene product) on fMET-Val synthesis and compared the relative effects of the primary and secondary promoters in the L10 operon on expression of the beta-subunit gene. The results show that the inhibitory effect of RNA polymerase on beta-subunit synthesis and the stimulatory effect of L factor occur before formation of the first dipeptide bond. In this in vitro system, the secondary promoters account for about 50% of the total fMet-Val synthesized. Although the primary promoter is sensitive to guanosine 5'-diphosphate 3'-diphosphate in vitro, the secondary promoters are not affected by this nucleotide.
质粒pNF1337和pNF1341含有L10操纵子的一部分，包括RNA聚合酶β亚基基因，已被用作体外模板来研究β亚基基因的表达。在这些研究中，测量的是β亚基第一个二肽fMet-Val的合成，而不是整个蛋白质的合成。通过使用这个二肽系统，我们研究了RNA聚合酶全酶和L因子（nus A基因产物）对fMET-Val合成的影响，并比较了L10操纵子中初级启动子和次级启动子对β亚基基因表达的相对影响。结果表明，RNA聚合酶对β亚基合成的抑制作用和L因子的刺激作用发生在第一个二肽键形成之前。在这个体外系统中，次级启动子占合成的总fMet-Val的约50%。虽然初级启动子在体外对鸟苷5'-二磷酸3'-二磷酸敏感，但次级启动子不受该核苷酸的影响。
