Cazenave C, Uhlenbeck O C
Department of Chemistry and Biochemistry, University of Colorado, Boulder 80309-0215.
Proc Natl Acad Sci U S A. 1994 Jul 19;91(15):6972-6. doi: 10.1073/pnas.91.15.6972.
In an attempt to synthesize an oligoribonucleotide by run-off transcription by bacteriophage T7 RNA polymerase, a major transcript was produced that was much longer than expected. Analysis of the reaction indicated that the product resulted from initial DNA-directed run-off transcription followed by RNA template-directed RNA synthesis. This reaction occurred because the RNA made from the DNA template displayed self-complementarity at its 3' end and therefore could form an intra- or intermolecular primed template. In reactions containing only an RNA template, the rate of incorporation of NTPs was quite comparable to DNA-dependent transcription. RNA template-directed RNA synthesis has been found to occur with a great number of oligoribonucleotides, even with primed templates that are only marginally stable. In one instance, we observed a multistep extension reaction converting the oligonucleotide into a final product longer than twice its original length. Presumably, such a process could have generated some of the RNAs found to be efficiently replicated by T7 RNA polymerase.
为了通过噬菌体T7 RNA聚合酶的连续转录来合成寡核糖核苷酸，产生了一种主要转录本，其长度比预期长得多。对该反应的分析表明，产物是由最初的DNA指导的连续转录，随后是RNA模板指导的RNA合成产生的。该反应发生是因为由DNA模板产生的RNA在其3'端显示出自我互补性，因此可以形成分子内或分子间引发的模板。在仅含有RNA模板的反应中，NTP的掺入速率与DNA依赖性转录相当。已发现RNA模板指导的RNA合成可与大量寡核糖核苷酸发生，即使是仅具有微弱稳定性的引发模板也是如此。在一个实例中，我们观察到一个多步延伸反应，将寡核苷酸转化为长度超过其原始长度两倍的最终产物。据推测，这样的过程可能产生了一些被发现能被T7 RNA聚合酶有效复制的RNA。
