The positive regulator CfaD overcomes the repression mediated by histone-like protein H-NS (H1) in the CFA/I fimbrial operon of Escherichia coli.
CFA/I fimbriae of enterotoxigenic Escherichia coli are expressed at 37 degrees C and not at 20 degrees C. Expression of CFA/I fimbriae requires two DNA regions (regions 1 and 2) which are separated by 40 kb on the wild type plasmid. Region 2 encodes a protein (CfaD) which activates the promoter in region 1. We investigated whether the histone-like protein H-NS (H1) of E.coli is involved in the temperature regulated expression of CFA/I fimbriae. As demonstrated recently with other temperature regulated genes, a mutation in the gene coding for this nucleoid-associated H-NS (H1) protein resulted in derepression of CFA/I expression. CFA/I fimbriae were now expressed both at 20 degrees C and 37 degrees C. More strinkingly, the positive regulator CfaD was not needed for CFA/I expression in an H-NS- strain. This indicates that CfaD diminishes an inhibitory effect of the H-NS nucleoid-associated protein. We also showed that in the H-NS- strain the CfaD protein still has a positive effect on the transcription of CFA/I.
Jordi
B J
BJ
Department of Bacteriology, Faculty of Veterinary Medicine, University of Utrecht, The Netherlands.
Dagberg
B
B
de Haan
L A
LA
Hamers
A M
AM
van der Zeijst
B A
BA
Gaastra
W
W
Uhlin
B E
BE
D000942:Antigens, Bacterial / Q000096:biosynthesis / Q000235:genetics*; D001345:Autoradiography; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D015152:Blotting, Northern; D015153:Blotting, Western; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism; D029968:Escherichia coli Proteins; D036781:Fimbriae Proteins; D010861:Fimbriae, Bacterial / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D008969:Molecular Sequence Data; D009876:Operon; D010957:Plasmids; D016133:Polymerase Chain Reaction; D012329:RNA, Bacterial / Q000378:metabolism; D013696:Temperature; D014158:Transcription, Genetic; D001616:beta-Galactosidase / Q000378:metabolism
D000942:Antigens, Bacterial; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; C069375:CfaD protein, E coli; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C031908:H-NS protein, bacteria; D012329:RNA, Bacterial; C022924:colonization factor antigens; D036781:Fimbriae Proteins; D001616:beta-Galactosidase