Identification and characterization of growth suppressors of Escherichia coli strains lacking phosphorolytic ribonucleases.
Identification and characterization of growth suppressors of Escherichia coli strains lacking phosphorolytic ribonucleases.
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缺乏磷酸解核糖核酸酶的大肠杆菌菌株生长抑制剂的鉴定和表征。
DOI：
10.1128/jb.01716-08
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发表时间：
2009
影响因子：
3.2
通讯作者：
Jain,Chaitanya
中科院分区：
文献类型：
--
作者：
Jain,Chaitanya
RNA酶参与所有生物体中RNA代谢的关键方面。已知两类从末端消化RNA的RNA酶（外切RNA酶）：使用水作为亲核试剂催化RNA降解的RNA酶（水解RNA酶）和使用无机磷酸盐的RNA酶（磷酸解RNA酶）。以前已经表明，缺乏两种已知的大肠杆菌磷酸化核糖核酸酶，多核苷酸磷酸化酶和核糖核酸酶PH，导致显着的生长和核糖体装配缺陷。为了研究这些缺陷的基础，进行了生长抑制剂的筛选。大多数的抑制突变被发现位于inflaminR，它编码一氧化氮（NO）敏感的转录抑制因子。进一步的分析表明，抑制因子的功能不是通过使RNase R失活，而是通过引起编码水解RNase R的下游基因的过表达。另外的研究表明，另一种水解核糖核酸酶，核糖核酸酶II的过度表达，同样抑制了生长缺陷。这些结果表明，磷酸化RNA酶的强劲的细胞生长和有效的核糖体组装的需求可以绕过增加的表达水解RNA酶。
RNases are involved in critical aspects of RNA metabolism in all organisms. Two classes of RNases that digest RNA from an end (exo-RNases) are known: RNases that use water as a nucleophile to catalyze RNA degradation (hydrolytic RNases) and RNases that use inorganic phosphate (phosphorolytic RNases). It has been shown previously that the absence of the two knownEscherichia coliphosphorolytic RNases, polynucleotide phosphorylase and RNase PH, leads to marked growth and ribosome assembly defects. To investigate the basis for these defects, a screen for growth suppressors was performed. The majority of suppressor mutations were found to lie withinnsrR, which encodes a nitric oxide (NO)-sensitive transcriptional repressor. Further analysis showed that the suppressors function not by inactivatingnsrRbut by causing overexpression of a downstream gene that encodes a hydrolytic RNase, RNase R. Additional studies revealed that overexpression of another hydrolytic RNase, RNase II, similarly suppressed the growth defects. These results suggest that the requirement for phosphorolytic RNases for robust cellular growth and efficient ribosome assembly can be bypassed by increased expression of hydrolytic RNases.