| RNA-linked nascent DNA pieces in phage T7-infected Escherichia coli. II. Primary structure of the RNA portion (1979) | |||||||||||||
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| 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. | |||||||||||||
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