PROMOTER DETERMINANTS FOR ESCHERICHIA-COLI RNA-POLYMERASE HOLOENZYME CONTAINING SIGMA(38) (THE RPOS GENE-PRODUCT)

Sequence determinants responsible for promoter recognition by RNA poly merase hotoenzyme containing sigma(38), the rpoS gene product, were an alyzed. In a previous study [Tanaka et al. (1993) Proc. Natl. Acad. Sc i. USA, 90, 3511-3515], Escherichia coli promoters were classified int o three groups: promoters recognized only by RNA polymerase holoenzyme containing sigma(70) (E sigma(70)); promoters recognized preferential ly by that containing sigma(38) (E sigma(38)); promoters recognized by both E sigma(70) and E sigma(38). As representatives of each group of promoter, we chose the alaS, fic and lacUV5 promoters. Making use of a restriction enzyme site inserted between the -10 and -35 hexamer seq uences, promoters were divided into the upstream (UE) and downstream ( DE) elements. These UEs and DEs were combined in all possible combinat ions and used for in vitro transcription reactions. Promoters containi ng DE from the fic or lacUV5 promoter were found to be recognized by E sigma(38), while those containing DE from the alaS promoter were not. Moreover, fic DE alone functioned as an efficient promoter for E sigm a(38). Thus we conclude that the discrimination signal resides within the DE sequence. To test the activator response of E sigma(38), in vit ro transcription reactions were also performed with the gal and lac pr omoters. For both CRP-responsive P1 promoters, E sigma(38) was found t o be activated by the CRP-cAMP complex.