STIMULATORY EFFECT OF TREHALOSE ON FORMATION AND ACTIVITY OF ESCHERICHIA-COLI RNA-POLYMERASE E-SIGMA(38) HOLOENZYME

The intracellular concentration of trehalose increases in the stationa ry-phase cells of Escherichia coil. The effects of trehalose on transc ription in vitro by E. coli RNA polymerase were compared for two holoe nzymes, E sigma(70) and E sigma(38), which were reconstituted from pur ified core enzyme and either sigma(70) (the major a at the exponential growth phase) or sigma(38) (the essential a at the stationary growth phase), respectively. The optimum trehalose concentration giving maxim um transcription by E sigma(38) was higher than that by E sigma(70). T ranscription activation by trehalose was attributed to both increased formation of E sigma(38) holoenzyme and increased transcription initia tion by E sigma(38) from sigma(38)-dependent promoters. The activation of E sigma(38) by trehalose was additive with the transcription enhan cement by decreased superhelicity of template DNA prepared from statio nary-phase cells. We thus propose that the selective activation of tra nscription by E sigma(38) holoenzyme takes place in the presence of sp ecific conditions and factors present under stress conditions.