Bralley Patricia, Chang Samantha A, Jones George H
Department of Biology, Emory University, Atlanta, GA 30322, USA.
J Bacteriol. 2005 Sep;187(17):5927-36. doi: 10.1128/JB.187.17.5927-5936.2005.
We have analyzed the distribution of RNA nucleotidyltransferases from the family that includes poly(A) polymerases (PAP) and tRNA nucleotidyltransferases (TNT) in 43 bacterial species. Genes of several bacterial species encode only one member of the nucleotidyltransferase superfamily (NTSF), and if that protein functions as a TNT, those organisms may not contain a poly(A) polymerase I like that of Escherichia coli. The genomes of several of the species examined encode more than one member of the nucleotidyltransferase superfamily. The function of some of those proteins is known, but in most cases no biochemical activity has been assigned to the NTSF. The NTSF protein sequences were used to construct an unrooted phylogenetic tree. To learn more about the function of the NTSFs in species whose genomes encode more than one, we have examined Bacillus halodurans. We have demonstrated that B. halodurans adds poly(A) tails to the 3' ends of RNAs in vivo. We have shown that the genes for both of the NTSFs encoded by the B. halodurans genome are transcribed in vivo. We have cloned, overexpressed, and purified the two NTSFs and have shown that neither functions as poly(A) polymerase in vitro. Rather, the two proteins function as tRNA nucleotidyltransferases, and our data suggest that, like some of the deep branching bacterial species previously studied by others, B. halodurans possesses separate CC- and A-adding tRNA nucleotidyltransferases. These observations raise the interesting question of the identity of the enzyme responsible for RNA polyadenylation in Bacillus.
我们分析了43种细菌中包括多聚腺苷酸聚合酶（PAP）和tRNA核苷酸转移酶（TNT）在内的RNA核苷酸转移酶家族的分布情况。几种细菌的基因仅编码核苷酸转移酶超家族（NTSF）的一个成员，如果该蛋白质发挥TNT的功能，那么这些生物体可能不含有像大肠杆菌那样的多聚腺苷酸聚合酶I。所检测的几种物种的基因组编码了不止一个核苷酸转移酶超家族成员。其中一些蛋白质的功能是已知的，但在大多数情况下，尚未赋予NTSF任何生化活性。利用NTSF蛋白质序列构建了一棵无根系统发育树。为了更多地了解基因组编码不止一个NTSF的物种中NTSF的功能，我们研究了嗜碱芽孢杆菌。我们已经证明嗜碱芽孢杆菌在体内会给RNA的3'末端添加多聚腺苷酸尾巴。我们已经表明嗜碱芽孢杆菌基因组编码的两个NTSF基因在体内均被转录。我们克隆、过量表达并纯化了这两种NTSF，结果表明它们在体外均不发挥多聚腺苷酸聚合酶的功能。相反，这两种蛋白质发挥tRNA核苷酸转移酶的功能，我们的数据表明，与之前其他人研究的一些进化分支较深的细菌物种一样，嗜碱芽孢杆菌拥有单独的添加CC和添加A的tRNA核苷酸转移酶。这些观察结果提出了一个有趣的问题，即芽孢杆菌中负责RNA聚腺苷酸化的酶的身份是什么。
