MOLECULAR CLONING OF THE DNA-LIGASE GENE FROM BACTERIOPHAGE-T4 .1. CHARACTERIZATION OF THE RECOMBINANTS

Fragments of the bacteriophage T4 genome containing the DNA ligase gene have been transferred to phage λ vectors. Recombinants containing this gene were selected by complementation of a ligase-deficient strain of Escherichia coli. The use of T4 DNA containing both hydroxymethylcytosine and cytosine permitted the recovery of a functional ligase gene, even though it contains target sequences for the restriction endonuclease used. Genetic and biochemical proof of the inclusion of the T4 DNA ligase gene was obtained. The position of the ligase gene and its direction of transcription have been determined relative to the targets for R.EcoRI and R.HindIII. Three R.EcoRI fragments, but only one R.HindIII fragment, are required for a functional ligase gene. The T4 DNA ligase gene can be transcribed effectively from any of the three major λ promoters and, in addition, phages including the three R.EcoRI fragments express the T4 gene in the prophage state when the major λ promoters are repressed. The apparent T4 promoter for the DNA ligase gene shows a complex genetic behaviour. © 1979.