Biosynthesis of RNA polymerase in Escherichia coli. XII. Noncoordinate synthesis of core enzyme subunits after suppression of cell growth.

In spite of the generally well-coordinated synthesis of RNA polymerase core enzyme subunits (alpha, beta and beta') in Escherichia coli, a situation was found during the growth transition from exponential to stationary phase in which this coordination was broken (the order of differential repression being alpha leads to beta' leads to beta; Kawakami et al. (1979). The present study indicates that, during a certain period of the growth transition, twice as much beta subunit is synthesized as beta' subunit and the overproduced beta subunit accumulates as the assembly intermediate alpha 2 beta complex, which is rapidly and preferentially degraded. Two independent factors, i.e., carbon source down-shift and oxygen depletion, were examined separately for their influence on the coordinated regulation of the synthesis of RNA polymerase subunits. The depletion of glucose added as a sole carbon source was accompanied by repression of the synthesis of all core enzyme subunits, while under the same conditions the differential rate of sigma subunit synthesis increased. In contrast, the sudden ending of the oxygen supply resulted in specific repression of the synthesis of only beta and beta' subunits but not of sigma and alpha subunits. The latter result may be explained by the autogenous repression of the rpoBC genes by a temporal increase in the amount of unused cytoplasmic RNA polymerase.