Biosynthesis of RNA polymerase in Escherichia coli

Summary

Effect of temperature-sensitive, assembly-defective mutations in Escherichia coli RNA polymerase β (rpoB) or β′ subunit gene (rpoC) was investigated on the expression of wild-type rpoB ⁺C⁺operon, which was introduced by infection of a lambda transducing phage λdrif ⁺ (rpoB ⁺)-6 after UV-irradiation of the mutant cells. In rpoB2·rpoB7 strain which accumulates assembly-intermediates, free α, α₂β complex and premature core, the expression of rpoB ⁺C⁺operon measured by the rate of β subunit synthesis was considerably inhibited whereas that of EF(translation elongation factor)-Tu, ribosomal proteins L1 and L7/L12, and some λ-coded proteins remained unaffected. On the other hand, the expression was enhanced specifically for only rpoB ⁺C⁺operon in either rpoC4 or rpoC1 mutants, which are defective in the association of α₂β complex and β′ subunit or the activation of premature core enzyme, respectively. Upon preincubation of the mutant cells at 42° C prior to phage infection, during which assembly intermediates degraded rapidly, the rate of β subunit synthesis relative to other phage-corded proteins increased remarkably in rpoB2·rpoB7 mutant as well as in rpoC4 and rpoC1 mutants. These observations strongly suggested the autogenous regulation for at least ββ′ (rpoB ⁺C⁺) operon by some trans-active diffusible protein complexes built of RNA polymerase subunits. Nature of the regulatory molecules is discussed.