The occurrence of multiple RNA polymerase specificity determinants (sigma factors) within a single organism represents a powerful mechanism for gene control. The substitution of one for another of these proteins on the core transcriptase could turn on or suppress a large number of genes by a single regulatory event. At least nine unique sigma-like proteins are present in the bacterium Bacillus subtilis. Five of these proteins are present during vegetative growth while four of them are found only during a simple form of differentiation (sporulation) that the bacterium undergoes as a consequence of nutritional stress. We propose to investigate the function and regulation of two (sigma B, Sigma E) of these sigma factors. Sigma B and Sigma E differ in their abundance, time of appearance during growth and development, and the method by which they participate in the activation of their respective regulons. We will analyze the function of Sigma B as well as the factors which influence its activity by characterizing by genetic and physiological means a collection of previously isolated mutations which enhance transcription form a Sigma B-dependent promoter, map proximal to the Sigma B structural gene (sigB), and confer an aberrant morphology on cells that carry them. We will investigate the regions of the Sigma E structural gene (sigE) which influence its activity and synthesis by analyzing mutations which alter these properties. We will explore in depth the phenomenon of "processing" of Sigma E from an inactive precursor molecule. This will involve a "suppression analysis" of a number of mutations in elements of the "processing machinery" as well as sigE itself. The basis of the suppressions will be characterized genetically, immunologically and biochemically.
