Zurawski G, Elseviers D, Stauffer G V, Yanofsky C
Proc Natl Acad Sci U S A. 1978 Dec;75(12):5988-92. doi: 10.1073/pnas.75.12.5988.
We have isolated two regulatory mutants altered in the leader region of the Escherichia coli tryptophan (trp) operon. In one mutant, trpL29, the AUG translation start codon for the trip leader peptide is replaced by AUA. The other mutant, trpL75, has a G leads to A change at residue 75, immediately after the UGA translation stop codon for the trp leader peptide. In vivo, trpL29 and trpL75 increase the efficiency of transcription termination at the trp attenuator 3- to 5-fold. trpL29 and trpL75 also fail to respond fully to tryptophan starvation and other conditions that normally relieve transcription termination at the trp attenuator. The trpL29 mutation, which presumably reduces synthesis of the trp leader peptide, is cis dominant. The effect of starvation for a number of the amino acids in the trp leader peptide was determined. Only starvation for tryptophan and arginine, amino acids that occur at residues 10, 11, and 12 of the 14-residue trp leader peptide, elicits relief of transcription termination. Our findings suggest that translation of trp leader RNA is involved in regulation of transcription termination at the attenuator. A model is discussed in which the location of the ribosome synthesizing the leader peptide is communicated to the RNA polymerase transcribing the leader region.
我们已经分离出了两个在大肠杆菌色氨酸（trp）操纵子前导区发生改变的调控突变体。在一个突变体trpL29中，色氨酸前导肽的AUG翻译起始密码子被AUA取代。另一个突变体trpL75在色氨酸前导肽的UGA翻译终止密码子之后的第75位残基处发生了G到A的改变。在体内，trpL29和trpL75使色氨酸衰减子处的转录终止效率提高了3至5倍。trpL29和trpL75也不能对色氨酸饥饿和其他通常能缓解色氨酸衰减子处转录终止的条件做出充分反应。trpL29突变可能减少了色氨酸前导肽的合成，它是顺式显性的。我们测定了色氨酸前导肽中多种氨基酸饥饿的影响。只有色氨酸和精氨酸饥饿，即在14个残基的色氨酸前导肽中位于第10、11和12位残基的氨基酸饥饿，能引起转录终止的缓解。我们的发现表明，色氨酸前导RNA的翻译参与了衰减子处转录终止的调控。本文讨论了一个模型，即合成前导肽的核糖体的位置会传递给转录前导区的RNA聚合酶。
