Synthesis and biological activity of a lambda pseudo operator.

The chemical and enzymatic syntheses of bacteriophage lambda pseudo operator DNA are described. The 17 base-paired duplex contains the DNA which has been proposed as the binding site for cI repressor protein. The synthetic duplex is twofold symmetric and represents the best possible nucleotide summation of the six proposed operator sites in the leftward and rightward operators. However, it does not correspond exactly to any single proposed operator sequence. The chemical synthesis includes the deoxyoligonucleotides d(T-A-T-C-A-C), d(C-G-C-C-G-G-T-G-A-T-A), d(T-A-T-C-A-C-C), and d(G-G-C-G-G-T-G-A-T-A). These deoxyoligonucleotides were joined with T4 DNA ligase to form d(T-A-T-C-A-C-C-G-C-C-G-G-T-G-A-T-A) and d(T-A-T-C-A-C-C-G-G-C-G-G-T-G-A-T-A). The cI repressor protein was found to bind to the duplex formed from these two segments.