ENZYME-SYSTEM FOR REPLICATION OF DUPLEX CIRCULAR DNA - REPLICATIVE FORM OF PHAGE PHI-X174

Viral single strands (SS) are converted to the duplex form (RF) by a soluble enzyme fraction from uninfected Escherichia coli. When reactions were supplemented with a soluble enzyme fraction from .vphi.X174-infected cells, replication .vphi.X174 superhelical RF I DNA was observed. The activity supplied by infected cells was absent in cells treated with chloramphenicol or in cells infected with a .vphi.X174 phage mutant in cistron A (cisA). A host function coded by the rep gene, essential in vivo for RF replication (but not for SS .fwdarw. RF), was supplied by enzyme fractions from either infected or uninfected cells. Based on complementation assays, the cisA-dependent and the rep-dependent proteins were each purified about 1000-fold. The synthetic products of the enzymatic reaction were identified as RF I and RF II in which viral (+) and complementary (-) strands were newly synthesized.