COMPARISON OF THE EXPRESSION OF THE 7 RIBOSOMAL-RNA OPERONS IN ESCHERICHIA-COLI
COMPARISON OF THE EXPRESSION OF THE 7 RIBOSOMAL-RNA OPERONS IN ESCHERICHIA-COLI
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DOI：
10.1002/j.1460-2075.1992.tb05511.x
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发表时间：
1992-11-01
期刊：
影响因子：
11.4
通讯作者：
SQUIRES, CL
中科院分区：
文献类型：
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作者：
CONDON, C;PHILIPS, J;SQUIRES, CL
我们比较了大肠杆菌7种核糖体RNA操纵子（rrn）的表达及其对各种生理和遗传扰动的反应。我们使用了一组rrn启动子融合构建物在它们的天然染色体位置来检测染色体位置对rrn操纵子表达的影响，并使用了相同的一组融合物在lambda溶原上检测独立于染色体背景的内在启动子强度。在其原生染色体位置，rrnH操纵子的表达明显低于预期。这种影响不是由于启动子活性弱，而是取决于生长介质。在最低培养基中，rrnE操纵子相对于其他核糖体操纵子的启动子活性降低，因此似乎具有异常的生长速率调节。核糖体RNA操纵子对氨基酸饥饿表现出不同的反应；rnd的表达受抑制最明显。随着温度的变化（从30℃到42℃），rrn的转录量只有轻微的增加，而且单个操纵子之间的差异非常小。rrnG操纵子对rrn转录激活子Fis缺失的反应明显低于其他核糖体RNA操纵子，因此似乎降低了Fis介导的转激活。最后，采用染色体融合菌株研究灭活各rrn操纵子对其生长速率的影响。在快速生长条件下，某些rrn操纵子的丢失导致复杂培养基上生长速率的轻微下降。
We have compared the expression of the seven ribosomal RNA operons (rrn) of Escherichia coli and their responses to a variety of physiological and genetic perturbations. We used a set of rrn promoter fusion constructs in their native chromosomal positions to examine effects of chromosomal location on rrn operon expression and the same set of fusions on lambda lysogens to assay intrinsic promoter strengths independent of chromosome context. In its native chromosomal location, expression of the rrnH operon was significantly lower than expected. This effect was not attributable to weak promoter activity and was dependent on the growth medium. The rrnE operon had reduced promoter activity relative to the other ribosomal operons in minimal medium and thus appears to have abnormal growth rate regulation. The ribosomal RNA operons showed varied responses to amino acid starvation; expression of rrnD was inhibited most. There was only a slight increase in rrn transcription in response to a temperature shift (30-degrees-C to 42-degrees-C) and the differences between individual operons was very small. The rrnG operon showed a significantly lower response than the other ribosomal RNA operons to a depletion of the rrn transcription activator, Fis, and thus appears to have decreased Fis-mediated transactivation. Finally, the chromosomal fusion strains were used to study the effect on growth rate of inactivating each rrn operon. In fast growth conditions, loss of certain rrn operons caused subtle decreases in growth rate on complex medium.