EXPRESSION OF PEPTIDE-CHAIN RELEASE FACTOR-II REQUIRES HIGH-EFFICIENCY FRAMESHIFT
EXPRESSION OF PEPTIDE-CHAIN RELEASE FACTOR-II REQUIRES HIGH-EFFICIENCY FRAMESHIFT
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DOI：
10.1038/322273a0
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发表时间：
1986-07-17
期刊：
影响因子：
64.8
通讯作者：
CASKEY, CT
中科院分区：
文献类型：
--
作者：
CRAIGEN, WJ;CASKEY, CT
肽链释放因子是参与多肽生物合成的终止密码子依赖性终止的可溶性蛋白质。在大肠杆菌中，两个释放因子是肽链终止所必需的：释放因子1（RF 1）指定UAG和UAA依赖性终止，而释放因子2（RF 2）指定UGA和UAA依赖性终止1。相对于其他翻译因子，释放因子的浓度较低2，这表明它们的表达受到严格调控，因此难以研究它们的结构-功能关系。RF 1和RF 2表现出显着的序列同源性，可能反映了它们相似的功能，也许是一个共同的进化起源3。DNA和肽序列分析表明存在一种独特的RF 2自身调控机制，其中读框内的UGA终止密码子需要RF 2基因编码区内的强制性+1移码。在这份报告中，我们提出了与自体调节RF 2一致的体外实验结果。此外，我们使用RF 2-LacZ基因融合体来证明自体调节至少部分地通过在框内终止密码子处的提前终止而发生，因为该终止密码子的缺失导致RF 2-LacZ融合蛋白的过量产生。在这个提前终止密码子处的移码以50%的非常高的比率发生。
Peptide chain release factors are soluble proteins that participate in the stop codon-dependent termination of polypeptide biosynthesis. InEscherichia coli, two release factors are necessary for peptide chain termination: release factor 1 (RF1) specifies UAG-and UAA-dependent termination whereas release factor 2 (RF2) specifies UGA- and UAA-dependent termination1. Release factors are found in low concentrations relative to other translation factors2, suggesting that their expression is tightly regulated and, accordingly, making the study of their structure–function relationship difficult. RF1 and RF2 exhibit significant sequence homology, probably reflecting their similar functions and perhaps a common evolutionary origin3. DNA and peptide sequencing have suggested the existence of a unique mechanism for the autogenous regulation of RF2 in which an in-frame UGA stop codon requires an obligatory +1 frameshift within the coding region of theRF2gene. In this report we presentin vitroexperimental results consistent with the autogenous regulation ofRF2. Additionally, we usedRF2-lacZgene fusions to demonstrate that autogenous regulation occurs, at least in part, by premature termination at the in-frame stop codon, since deletion of this stop codon leads to overproduction of the RF2–LacZ fusion protein. Frameshifting at this premature termination codon occurs at the remarkably high rate of 50%.