Polyadenylation promotes degradation of 3′-structured RNA by the Escherichia coli mRNA degradosome in vitro
Polyadenylation promotes degradation of 3′-structured RNA by the Escherichia coli mRNA degradosome in vitro
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DOI：
10.1074/jbc.274.7.4009
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发表时间：
1999-02-12
影响因子：
4.8
通讯作者：
Higgins, CF
中科院分区：
文献类型：
--
作者：
Blum, E;Carpousis, AJ;Higgins, CF
多聚腺苷酸化导致细菌mRNA的不稳定我们研究了多聚腺苷酸化在纯化的大肠杆菌降解体体外降解RNA中的作用。具有掺入稳定茎环结构中的3 '-末端的RNA分子不能容易地被纯化的多核苷酸磷酸化酶或被降解体降解，即使降解体含有通常促进结构化RNA降解的活性RhlB解旋酶。降解体的核糖核酸外切活性是由于多核苷酸磷酸化酶，而不是最近报道的RNA酶E的纯化片段所表现出的核糖核酸外切活性（Huang，H.，Liao，J.，和Cohen，S，N.（1998）Nature 391，99-102），添加3 '-poly（A）尾刺激降解体的降解，少至5个腺苷残基就足以实现这种刺激，并且通用序列同样有效。数据表明，降解体需要一个单链的“立足点”3'到二级结构，以有效地识别和降解RNA分子;聚腺苷酸化可以提供这个单链的3'端。值得注意的是，oligo（a）和oligo（U）尾不能刺激降解;至少对于oligo（a），这可能是由于形成了G四联体结构，使得3 '端不可接近。3 '-oligo（U）序列的不可接近性可能在由Rho非依赖性终止子产生的RNA分子的稳定中起作用。
Polyadenylation contributes to the destabilization of bacterial mRNA We have investigated the role of polyadenylation in the degradation of RNA by the purified Eseherichia coil degradosome in vitro. RNA molecules with 3'-ends incorporated into a stable stem-loop structure could not readily be degraded by purified polynucleotide phosphorylase or by the degradosome, even though the degradosome contains active RhlB helicase which normally facilitates degradation of structured RNA. The exoribonucleolytic activity of the degradosome was due to polynucleotide phosphorylase, rather than the recently reported exonucleolytic activity exhibited by a purified fragment of RNase E (Huang, H,, Liao, J., and Cohen, S, N. (1998) Nature 391, 99-102), Addition of a 3'-poly(A) tail stimulated degradation by the degradosome, As few as 5 adenosine residues were sufficient to achieve this stimulation, and generic sequences were equally effective. The data show that the degradosome requires a single-stranded "toehold" 3' to a secondary structure to recognize and degrade the RNA molecule efficiently; polyadenylation can provide this single-stranded 3'-end. Significantly, oligo(a) and oligo(U) tails were unable to stimulate degradation; for oligo(a), at least, this is probably due to the formation of a G quartet structure which makes the 3'-end inaccessible. The inaccessibility of 3'-oligo(U) sequences is likely to have a role in stabilization of RNA molecules generated by Rho-independent terminators.