H-NS is a repressor of the Proteus mirabilis urease transcriptional activator gene ureR.
Expression of Proteus mirabilis urease is governed by UreR, an AraC-like positive transcriptional activator. A poly(A) tract nucleotide sequence, consisting of A(6)TA(2)CA(2)TGGTA(5)GA(6)TGA(5), is located 16 bp upstream of the sigma(70)-like ureR promoter P2. Since poly(A) tracts of DNA serve as binding sites for the gene repressor histone-like nucleoid structuring protein (H-NS), we measured beta-galactosidase activity of wild-type Escherichia coli MC4100 (H-NS(+)) and its isogenic derivative ATM121 (hns::Tn10) (H-NS(-)) harboring a ureR-lacZ operon fusion plasmid (pLC9801). beta-Galactosidase activity in the H-NS(-) host strain was constitutive and sevenfold greater (P < 0.0001) than that in the H-NS(+) host. A recombinant plasmid containing cloned P. mirabilis hns was able to complement and restore repression of the ureR promoter in the H-NS(-) host when provided in trans. Deletion of the poly(A) tract nucleotide sequence from pLC9801 resulted in an increase in beta-galactosidase activity in the H-NS(+) host to nearly the same levels as that observed for wild-type pLC9801 harbored by the H-NS(-) host. Urease activity in strains harboring the recombinant plasmid pMID1010 (encoding the entire urease gene cluster of P. mirabilis) was equivalent in both the H-NS(-) background and the H-NS(+) background in the presence of urea but was eightfold greater (P = 0.0001) in the H-NS(-) background in the absence of urea. We conclude that H-NS represses ureR expression in the absence of urea induction.
Coker
C
C
Department of Microbiology, University of Maryland School of Medicine, Baltimore, Maryland 21201, USA.
Bakare
O O
OO
Mobley
H L
HL
D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli; D015964:Gene Expression Regulation, Bacterial; D011061:Poly A; D011401:Promoter Regions, Genetic; D011513:Proteus mirabilis / Q000235:genetics / Q000378:metabolism*; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D015534:Trans-Activators / Q000235:genetics*; D014510:Urease / Q000096:biosynthesis
D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; C031908:H-NS protein, bacteria; D012097:Repressor Proteins; D015534:Trans-Activators; C119767:UreR protein, bacteria; D011061:Poly A; D014510:Urease