Johnson M D, Popowski J, Cao G J, Shen P, Sarkar N
Boston Biomedical Research Institute, MA 02114, USA.
Mol Microbiol. 1998 Jan;27(1):23-30. doi: 10.1046/j.1365-2958.1998.00649.x.
To determine whether the RNA of bacterial viruses is polyadenylated like bacterial mRNAs, pulse-labelled as well as the steady-state population of bacteriophage T7-specific transcripts were examined for the presence of poly(A) tracts by binding to oligo(dT) cellulose followed by hybridization with specific gene probes. Representatives of all classes of bacteriophage-specific mRNA--early, middle and late--were found to be polyadenylated. This conclusion was confirmed by screening the products of oligo(dT)-dependent cDNA synthesis. A cDNA library was prepared from RNA synthesized after bacteriophage T7 infection and the sequence of bacteriophage-specific clones was determined to define the sites of polyadenylation. About half of the clones were polyadenylated near the end of a protein-coding region, one of them at the site of post-transcriptional processing by RNase III. Other clones were polyadenylated within protein-coding regions. These observations suggest that polyadenylation occurs after the nucleolytic processing of primary transcripts and in some cases also after mRNA degradation has already begun.
为了确定细菌病毒的RNA是否像细菌mRNA一样被多聚腺苷酸化，通过与寡聚（dT）纤维素结合，然后与特定基因探针杂交，对脉冲标记以及噬菌体T7特异性转录本的稳态群体进行了多聚（A）序列的检测。发现所有类别的噬菌体特异性mRNA——早期、中期和晚期——的代表都被多聚腺苷酸化。通过筛选寡聚（dT）依赖性cDNA合成产物证实了这一结论。从噬菌体T7感染后合成的RNA制备了一个cDNA文库，并确定了噬菌体特异性克隆的序列以确定多聚腺苷酸化位点。大约一半的克隆在蛋白质编码区末端附近被多聚腺苷酸化，其中一个在RNase III进行转录后加工的位点。其他克隆在蛋白质编码区内被多聚腺苷酸化。这些观察结果表明，多聚腺苷酸化发生在初级转录本的核酸酶加工之后，在某些情况下也发生在mRNA降解已经开始之后。
