Replication of colicin E1 plasmid DNA in cell extracts. II. Selective synthesis of early replicative intermediates.

The major products of colicin E1 plasmid DNA synthesis in cell extracts are completely replicated molecules and a class of molecules containing newly synthesized small DNA fragments. The addition of 10% glycerol and/or 2 mM spermidine to extracts blocks synthesis of completely replicated molecules while enhancing synthesis of molecules containing newly synthesized DNA fragments. The latter molecules, which contain on the average two DNA fragments of approximately 6 S, are early replicative intermediates for synthesis of completely replicated molecules. Synthesis of the intermediates is sensitive to rifampicin and depends on RNA synthesis. RNA components are linked to the 6S DNA molecules.