We are determining the biological role of the T4 bacteriophage induced enzymes, polynucleotide kinase and RNA ligase. The products of these genes are normally not required for T4 development because of the presence of the host litA gene which may be able to substitute for them under normal conditions. The host litA gene interacts with another E. coli gene, the litB gene. We are mapping and attempting to obtain DNA clones of the host litA and litB genes with the eventual aim of determining the role of the products of these genes in uninfected bacteria. We have also discovered a cis-acting site on T4 DNA which interacts with the host lit genes. We have cloned the DNA which includes this site and are sequencing the clones from both wild type and mutant strains.