COMPETITION BETWEEN FRAMESHIFTING, TERMINATION AND SUPPRESSION AT THE FRAMESHIFT SITE IN THE ESCHERICHIA-COLI RELEASE FACTOR-II MESSENGER-RNA
COMPETITION BETWEEN FRAMESHIFTING, TERMINATION AND SUPPRESSION AT THE FRAMESHIFT SITE IN THE ESCHERICHIA-COLI RELEASE FACTOR-II MESSENGER-RNA
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DOI：
10.1093/nar/21.22.5074
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发表时间：
1993-11-11
影响因子：
14.9
通讯作者：
TATE, WP
中科院分区：
文献类型：
--
作者：
ADAMSKI, FM;DONLY, BC;TATE, WP
在体外，通过添加UGA抑制因子tRNA，利用耦合转录-翻译系统测定了释放因子-2 (RF-2) mRNA移框、终止和抑制位点之间的竞争。用含有trpE-prfB融合基因的质粒对表达系统进行编程，以便可以测量每个竞争事件的产物。随着抑制因子tRNA浓度的增加，读取产物的增加以终止和移框产物为代价，表明这三个过程是直接竞争的。编码序列末端的内部UGA终止密码子的读通率大于自然UGA终止密码子的读通率。结果表明，这种增强的抑制可能反映了释放因子对内部停止密码子的解码速度较慢，从而使抑制具有竞争优势。移码位点的内部UGAC停止信号被认为是一个相对较差的信号，但此外，释放因子可能无法识别mRNA处于这种受限状态的信号。因此，当释放因子解码停止信号时，由于这种较长的暂停，移帧事件本身将与体内终止更具竞争性。
Competition between frameshifting, termination, and suppression at the frameshifting site in the release factor-2 (RF-2) mRNA was determined in vitro using a coupled transcription-translation system by adding a UGA suppressor tRNA. The expression system was programmed with a plasmid containing a trpE-prfB fusion gene so that each of the products of the competing events could be measured. With increasing concentrations of suppressor tRNA the readthrough product increased at the expense of both the termination and the frameshifting product indicating all three processes are in direct competition. The readthrough at the internal UGA termination codon was greater than that at the natural UGA termination codon at the end of the coding sequence. The results suggest that this enhanced suppression may reflect slower decoding of the internal stop codon by the release factor giving suppression a competitive advantage. The internal UGAC stop signal at the frameshift site has been proposed to be a relatively poor signal, but in addition the release factor may be less able to recognise the signal with the mRNA in such a constrained state. Consequently, the frameshifting event itself will be more competitive with termination in vivo because of this longer pause as the release factor is decoding the stop signal.