Seki T, Okazaki T
Nucleic Acids Res. 1979 Nov 24;7(6):1603-19. doi: 10.1093/nar/7.6.1603.
Short DNA chains were purified from phage T7 infected E. coli cells and 5' ends were labeled with 32P. By an alkali-treatment, pNp's rich in pAp and pCp were liberated from the T7 short DNA chains. After digestion of the [5'-32P] short DNA with the 3' to 5' exonuclease of T4 DNA polymerase, [5'-32P] mono- to pentaribonucleotides tipped with a deoxyribonucleotide residue at their 3' ends were isolated. 5' terminal ribonucleotides were; exclusively AMP in the penta- and the tetraribonucleotides, mostly CMP in the triribonucleotide and mainly CMP and AMP in di- and monoribonucleotides. The 5' terminal dinucleotide of the penta- and the tetraribonucleotides was pApC. The nucleotide sequence of the tetraribonucleotide was mainly pApCpCpN and some pApCpApN, where N was mainly A and C. These results indicate that oligoribonucleotides shorter than trinucleotide may result from in vivo degradation of the tetra- and pentaribonucleotides. A possibility that the tetra- and pentaribonucleotides with a 5' triphosphate terminus are the intact primers for the discontinuous T7 DNA replication is discussed.
从噬菌体T7感染的大肠杆菌细胞中纯化出短DNA链，并用32P标记其5'端。通过碱处理，从T7短DNA链中释放出富含pAp和pCp的pNp。用T4 DNA聚合酶的3'至5'外切核酸酶消化[5'-32P]短DNA后，分离出在其3'端带有脱氧核糖核苷酸残基的[5'-32P]单至五核糖核苷酸。5'末端核糖核苷酸在五核糖核苷酸和四核糖核苷酸中仅为AMP，在三核糖核苷酸中大多为CMP，在二核糖核苷酸和单核糖核苷酸中主要为CMP和AMP。五核糖核苷酸和四核糖核苷酸的5'末端二核苷酸为pApC。四核糖核苷酸的核苷酸序列主要为pApCpCpN和一些pApCpApN，其中N主要为A和C。这些结果表明，短于三核苷酸的寡核糖核苷酸可能是四核糖核苷酸和五核糖核苷酸在体内降解的产物。本文还讨论了具有5'三磷酸末端的四核糖核苷酸和五核糖核苷酸是T7 DNA不连续复制的完整引物的可能性。
