The enzymatic replication of DNA.

Enzymatic mechanisms of DNA replication have been investigated using small bacteriophages as probes to illuminate the cellular systems upon which they must rely during infection. Conversion of the circular, single-stranded DNAs of phages M13, G4, and phi X174 to their duplex forms has revealed the participation of diverse ways to start a new chain and a complex DNA polymerase III holoenzyme upon which all these systems depend for chain elongation. The phi X174 system, which is the most exacting and revealing of the host chromosomal replication pattern, includes at least twenty polypeptides for making the viral DNA into a duplex and multiplying the duplex. Resolution and purification of these numerous proteins is in train and their reconstitution into a "replisome"-like structure is envisioned.