Konarska M M, Sharp P A
Center for Cancer Research, Massachusetts Institute of Technology, Cambridge 02139.
Cell. 1990 Nov 2;63(3):609-18. doi: 10.1016/0092-8674(90)90456-o.
The DNA-dependent RNA polymerase of bacteriophage T7 efficiently and specifically replicates two structurally related RNAs, termed X and Y RNAs. Replication of both RNAs involves synthesis of complementary strands initiated with pppC and pppG. RNAs transcribed from DNA template containing the established sequences of X and Y RNAs were efficiently replicated by T7 RNA polymerase. Both RNAs possess palindromic sequences with a dual axis of symmetry, permitting formation of hairpin-, dumbbell-, or cloverleaf-type structures. The template must consist of RNA and not DNA sequence, and the terminal unpaired dinucleotides of the RNA are necessary for replication. Nucleotidyl transferase activity of E. coli adenylates the unpaired CCOH dinucleotide at the 3' end of a C strand of X RNA. This feature, as well as the length (64 nucleotides) and compact structure of X and Y RNAs, suggests that they may resemble tRNA molecules and tRNA-like structures at the 3' termini of many plant viral RNA genomes.
噬菌体T7的依赖DNA的RNA聚合酶能高效且特异性地复制两种结构相关的RNA，即X和Y RNA。这两种RNA的复制都涉及以pppC和pppG起始的互补链合成。从含有已确定的X和Y RNA序列的DNA模板转录而来的RNA能被T7 RNA聚合酶高效复制。这两种RNA都具有带有双对称轴的回文序列，允许形成发夹型、哑铃型或三叶草型结构。模板必须由RNA而非DNA序列组成，并且RNA的末端未配对二核苷酸对于复制是必需的。大肠杆菌的核苷酸转移酶使X RNA的C链3'端未配对的CCOH二核苷酸腺苷酸化。这一特征，以及X和Y RNA的长度（64个核苷酸）和紧凑结构，表明它们可能类似于许多植物病毒RNA基因组3'末端的tRNA分子和tRNA样结构。
