EXPRESSION OF THE LEUX GENE IN ESCHERICHIA-COLI - REGULATION AT TRANSCRIPTION AND TRANSFER-RNA PROCESSING STEPS
EXPRESSION OF THE LEUX GENE IN ESCHERICHIA-COLI - REGULATION AT TRANSCRIPTION AND TRANSFER-RNA PROCESSING STEPS
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DOI：
10.1016/0022-2836(87)90472-4
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发表时间：
1987-10-20
影响因子：
5.6
通讯作者：
ISHIHAMA, A
中科院分区：
文献类型：
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作者：
NOMURA, T;FUJITA, N;ISHIHAMA, A
大肠杆菌的 leuX (supP) 基因编码抑制 tRNA (tRNA6Leu)，在琥珀密码子处插入亮氨酸。体外和体内转录物的分析表明，该基因被组织成单个基因操纵子，携带其自己的启动子和ρ独立的萌发子，并且其初级转录物在野生型大肠杆菌的细胞中积累关于tRNA加工的作用。对未加工的初级转录本和成熟的tRNA6Leu的系统定量测量表明：（1）leuX基因的转录在体内受到严格控制，并且在体外受到ppGpp的抑制； (2) leuX基因的转录受生长速率依赖性控制；但 (3) 成熟 tRNA 的水平在各种生长条件下保持恒定。提出了一个模型，假设催化 leuX tRNA 加工第一步反应的酶是有限的，从而将成熟 tRNA6Leu 的水平保持在恒定水平，而不管未加工的初级转录物水平的变化。
The leuX (supP) gene of Escherichia coli codes for a suppressor tRNA (tRNA6Leu) that inserts leucine at the amber codon. Analysis of both in-vitro and in-vivo transcripts indicated that the gene is organized into a single gene operon, carrying its own promoter and .rho.-independent germinator, and its primary transcript accumulates in cells of wild-type E. coli with respect to tRNA processing. Systematic and quantitative measurements of both the unprocessed primary transcript and mature tRNA6Leu indicated that: (1) transcription of the leuX gene is under stringent control in vivo and is repressed in vitro by ppGpp; (2) transcription of the leuX gene is under growth rate-dependent control; but (3) the level of mature tRNA stays constant under various growth conditions. A model is proposed, which assumes that the enzyme catalyzing the first-step reaction in the leuX tRNA processing is limited, thereby keeping the level of mature tRNA6Leu at a constant level irrespective of changes in the level of the unprocessed primary transcript.