RNA-linked nascent DNA pieces in phage T7-infected Escherichia coli. II. Primary structure of the RNA portion

Abstract

Short DNA chains were purified from phage T7 Infected E. coll 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 pentaribonucleotldes 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 dl- 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 oligo-ribonucleotides shorter than trinucleotide may result from in vivo degradation of the tetra- and pentaribonucleotides. A possibility that the tetra- and pentaribonucleotldes with a 5′ triphosphate terminus are the intact primers for the discontinuous T7 DNA replication is discussed. © 1979 Information Retrieval Limited.