Utilization of trans-activated T4 uvsY regulatory signal for a high yield of cloned gene products.

We established an efficient system for a high-level production of foreign gene products in Escherichia coli using a trans-activated gene expression under the control of a phage T4 regulatory signal cloned in a plasmid by T4 phage infection. The transcriptional and translational signal of the T4 uvsY gene cloned in a plasmid was fused translationally with the coding region of the lacZ gene. When E. coli cells carrying the uvsY-lacZ plasmid were infected with cytosine-substituting T4 phage at a multiplicity of infection of 5, the amount of beta-galactosidase increased about 2-fold (trans-activation) over that without phage infection. We examined conditions for the high-level production of a trans-activated gene product. We found that a large number of T4-infected cells in a lysis-inhibition state could be obtained by a low multiplicity of infection with cytosine-substituting T4 phage. Thus it is now possible to attain a high yield of the trans-activated gene products. We discuss the advantage of the trans-activated T4 uvsY regulatory signal for production of foreign products.