首页 | 本学科首页   官方微博 | 高级检索  
     


Translational initiation at the coat-protein gene of phage MS2: native upstream RNA relieves inhibition by local secondary structure
Authors:Maarten H. de  Smit Jan van  Duin
Affiliation:Department of Biochemistry, Gorlaeus Laboratories, University of Leiden, Leiden, The Netherlands.
Abstract:Maximal translation of the coat-protein gene from RNA bacteriophage MS2 requires a contiguous stretch of native MS2 RNA that extends hundreds of nucleotides upstream from the translational start site. Deletion of these upstream sequences from MS2 cDNA plasmids results in a 30-fold reduction of translational efficiency. By site-directed mutagenesis, we show that this low level of expression is caused by a hairpin structure centred around the initiation codon. When this hairpin is destabilized by the introduction of mismatches, expression from the truncated messenger increases 20-fold to almost the level of the full-length construct. Thus, the translational effect of hundreds of upstream nucleotides can be mimicked by a single substitution that destabilizes the structure. The same hairpin is also present in full-length MS2 RNA, but there it does not Impair ribosome binding. Apparently, the upstream RNA somehow reduces the inhibitory effect of the structure on translational initiation. The upstream MS2 sequence does not stimulate translation when cloned in front of another gene, nor can unrelated RNA segments activate the coat-protein gene. Several possible mechanisms for the activation are discussed and a function in gene regulation of the phage is suggested.
Keywords:
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号