GUANOSINE 3'-DIPHOSPHATE 5'-DIPHOSPHATE IS NOT REQUIRED FOR GROWTH RATE-DEPENDENT CONTROL OF RIBOSOMAL-RNA SYNTHESIS IN ESCHERICHIA-COLI
GUANOSINE 3'-DIPHOSPHATE 5'-DIPHOSPHATE IS NOT REQUIRED FOR GROWTH RATE-DEPENDENT CONTROL OF RIBOSOMAL-RNA SYNTHESIS IN ESCHERICHIA-COLI
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DOI：
10.1073/pnas.87.14.5533
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发表时间：
1990-07-01
影响因子：
11.1
通讯作者：
GOURSE, RL
中科院分区：
文献类型：
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作者：
GAAL, T;GOURSE, RL
大肠杆菌中rRNA的合成至少受到两种调控系统的控制，即生长速率依赖性控制和严格控制。在各种生理条件下，rRNA合成速率与鸟苷3 ''-二磷酸5 ''-二磷酸（ppGpp）水平之间的负相关性导致人们推测ppGpp是通过抑制rrn p1启动子的转录来调节这两种控制机制的介体。最近，已经构建了relA-spoT-菌株，其中两个ppGpp合成途径最有可能已经被去除（M.卡谢尔，个人通信）。我们已经证实，这样的菌株不产生可检测的ppGpp，因此提供了一个直接的手段，用于测试参与的ppGpp在体内的rRNA合成的调节。严格的控制是通过测量氨基酸饥饿后rRNA合成来确定的，而生长速率控制是通过测量不同营养条件下rRNA合成来确定的。如所预期的，relA-spoT-菌株被放松以进行严格控制。然而，生长率依赖性调节并未受损。这些结果表明，生长速率调节可以发生在ppGpp的情况下，并暗示ppGpp不是介质，或至少不是唯一的介质，生长速率依赖性控制。因此，生长速率依赖性控制和严格控制可能利用不同的机制来调节稳定的RNA合成。
rRNA synthesis in Escherichia coli is subject to at least two regulation systems, growth rate-dependent control and stringent control. The inverse correlation between rRNA synthesis rates and guanosine 3''-diphosphate 5''-disphosphate (ppGpp) levels under various physiological conditions has led to the supposition that ppGpp is the mediator of both control mechanisms by inhibiting transcription from rrn p1 promoters. Recently, relA- spoT- strains have been constructed in which both ppGpp synthesis pathways most likely have been removed (M. Cashel, personal communication). We have confirmed that such strains produce no detectable ppGpp and therefore offer a direct means for testing the involvement of ppGpp in the regulation of rRNA synthesis in vivo. Stringent control was determined by measurement of rRNA synthesis after amino acid starvation, while growth rate control was determined by measurement of rRNA synthesis under different nutritional conditions. As expected, the relA- spoT- strain is relaxed for stringent control. However, growth rate-dependent regulation is unimpaired. These results indicate that growth rate regulation can occur in the absence of ppGpp and imply that ppGpp is not the mediator, or at least is not the sole mediator, of growth rate-dependent control. Therefore, growth rate-dependent control and stringent control may utilize different mechanisms for regulating stable RNA synthesis.