A REGION IN BACILLUS-SUBTILIS SIGMA(H) REQUIRED FOR SPO0A-DEPENDENT PROMOTER ACTIVITY

Spo0A activates transcription in Bacillus subtilis from promoters that are used by two types of RNA polymerase, RNA polymerase containing th e primary sigma factor, sigma(A), and RNA polymerase containing a seco ndary sigma factor, known as sigma(H). The region of sigma(A) near pos itions 356 to 359 is required for Spo0A-dependent promoter activation, possibly because SpoOA interacts with this region of sigma(A) at thes e promoters. To determine if the amino acids in the corresponding regi on of sigma(H) are also important in Spo0A-dependent promoter activati on, we examined the effects of single alanine substitutions at 10 posi tions in sigma(H) (201 to 210). Two alanine substitutions in sigma(H), at glutamine 201 (Q201A) and at arginine 205 (R205A), significantly d ecreased activity from the Spo0A-dependent, sigma(H)-dependent promote r spoIIA but did not affect expression from the sigma(H)-dependent, Sp o0A-independent promoters citGp2 and spoVG. Therefore, promoter activa tion by SpoOA requires homologous regions in sigma(A) and sigma(H). A mutant form of SpoOA, S231F, that suppresses the sporulation defect ca used by several amino acid substitutions in sigma(A) did not suppress the sporulation defects caused by the Q201A and R205A substitutions in sigma(H). This result and others indicate that different surfaces of SpoOA probably interact with sigma(A) and sigma(H) RNA polymerases.