SIGMA(S)-DEPENDENT GROWTH-PHASE INDUCTION OF THE CSGBA PROMOTER IN ESCHERICHIA-COLI CAN BE ACHIEVED IN-VIVO BY SIGMA(70) IN THE ABSENCE OF THE NUCLEOID-ASSOCIATED PROTEIN H-NS
A. Arnqvist et al., SIGMA(S)-DEPENDENT GROWTH-PHASE INDUCTION OF THE CSGBA PROMOTER IN ESCHERICHIA-COLI CAN BE ACHIEVED IN-VIVO BY SIGMA(70) IN THE ABSENCE OF THE NUCLEOID-ASSOCIATED PROTEIN H-NS, Molecular microbiology, 13(6), 1994, pp. 1021-1032
The stationary-phase-specific sigma factor sigma(S) (RpoS/KatF) is req
uired for Escherichia coli to induce expression of fibronectin-binding
curli organelles upon reaching stationary phase. We show that the csg
A gene which encodes the curlin subunit protein belongs to a dicistron
ic operon, csgBA. The transcriptional start site of csgBA was determin
ed and an AT-rich upstream activating sequence (UAS) required for tran
scriptional activation was identified. The pcsgBA promoter is not spec
ific for sigma(S) since the same promoter sequence can be used by E si
gma(70) in vivo in a strain lacking nucleoid-associated protein H-NS a
nd sigma(S). Transcription remained growth-phase induced and dependent
upon the UAS in such a double mutant. Furthermore, we demonstrate tha
t an additional operon, hdeAB, which is also dependent upon sigma(S) f
or transcription, can be transcribed by E sigma(70) in vivo in the abs
ence of H-NS by utilizing the phdeAB promoter. Two other genes known t
o be under the control of sigma(S) for expression, bolA and katE, rema
ined transcriptionally silent in the absence of H-NS. It is suggested
that a subset of E. coli promoters can be recognized by both E sigma(S
) and E sigma(70) in vivo but H-NS interacting with these sequences pr
events formation of succesful transcription-initiation complexes with
E sigma(70).