DNA replication by bacteriophage T4 proteins. The T4 43, 32, 44--62, And 45 proteins are required for strand displacement synthesis at nicks in duplex DNA.

The T4 bacteriophage gene 43 (T4 DNA polymerase), 32 (DNA helix-destabilizing protein), and 45 proteins and the complex of the gene 44 and 62 proteins are all required for DNA synthesis beginning at single-stranded breaks in duplex DNA. This synthesis occurs by strand displacement and is not dependent on ribonucleotides, the T4 gene 41 protein, or the T4 initiating protein, each of which is required to begin new chains on single-stranded templates. Electron microscopic analysis shows that duplex molecules with long single-stranded branches are the predominant products of this strand displacement synthesis.