Ultraviolet inducible protein associated with error prone repair in E. coli B

Abstract

Escherichia coli is affected in many ways by irradiation with ultraviolet light. New DNA is made containing gaps resulting from synthesis on damaged templates^1,2 and postreplication repair seals them by exchanging sections of DNA between daughter duplexes^3,4. The induction of mutations by ultraviolet light has been attributed to errors occurring during this type of repair^5–7 and so this repair has been called error prone. Ultraviolet radiation also results in pro-phage induction⁸, inhibition of respiration⁹, filamentous growth¹⁰ and the development of extra capacity to promote the survival¹¹ and mutagenesis¹² of irradiated infecting phages. All these events require the rec A⁺ and exr⁺ genes^{2,7,9,13–23} but the ways in which rec A⁺ and exr⁺ gene products affect such a diversity of postirradiation events are not known. One proposal is that they act in a single molecular process which in some way initiates all the phenomena described above and that the rec A⁺ exr⁺ dependent functions are inducible²³ by ultraviolet light and thus require the synthesis of new protein(s) in irradiated bacteria. Here I demonstrate that E. coli does indeed synthesise a protein in response to ultraviolet irradiation and that the synthesis of this protein is dependent on exr⁺ and rec A⁺ genes.