title: Negative effect of glucose on ompA mRNA stability: a potential role of cyclic AMP in the repression of hfq in Escherichia coli.
abstract: Glucose is a carbon source that is capable of modulating the level of cyclic AMP (cAMP)-regulated genes. In the present study, we found that the stability of ompA mRNA was reduced in Escherichia coli when glucose (40 mM) was present in Luria-Bertani (LB) medium. This effect was associated with a low level of cAMP induced by the glucose. The results were confirmed with an adenylyl cyclase mutant with low levels of cAMP that are not modulated by glucose. Northern blot and Western blot analyses revealed that the host factor I (Hfq) (both mRNA and protein) levels were downregulated in the presence of cAMP. Furthermore, we showed that a complex of cAMP receptor protein (CRP) and cAMP binds to a specific P3(hfq) promoter region of hfq and regulates hfq expression. The regulation of the hfq gene was confirmed in vivo using an hfq-deficient mutant transformed with an exogenous hfq gene containing the promoter. These results demonstrated that expression of hfq was repressed by the CRP-cAMP complex. The presence of glucose resulted in increased Hfq protein levels, which decreased ompA mRNA stability. An additional experiment showed that cAMP also increased the stability of fur mRNA. Taken together, these results suggested that the repression of Hfq by cAMP may contribute to the stability of other mRNA in E. coli.
authors.affiliation: Department of Biological Science and Technology, College of Biological Science and Technology, National Chiao Tung University, Hsinchu, Taiwan, Republic of China.
authors.forename: Hsiao-Hsien
authors.initials: HH
authors.lastname: Lin
authors.forename: Chi-Cheng
authors.initials: CC
authors.lastname: Hsu
authors.forename: Chi-Dung
authors.initials: CD
authors.lastname: Yang
authors.forename: Yih-Wei
authors.initials: YW
authors.lastname: Ju
authors.forename: Yi-Pei
authors.initials: YP
authors.lastname: Chen
authors.forename: Ching-Ping
authors.initials: CP
authors.lastname: Tseng
mesh_terms: D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism*; D015536:Down-Regulation; D004926:Escherichia coli / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics* / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D005947:Glucose / Q000378:metabolism*; D035001:Host Factor 1 Protein / Q000235:genetics* / Q000378:metabolism; D020871:RNA Stability; D012333:RNA, Messenger / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
chemical_list: D001425:Bacterial Outer Membrane Proteins; D029968:Escherichia coli Proteins; C087373:Hfq protein, E coli; D035001:Host Factor 1 Protein; D012333:RNA, Messenger; C078167:OMPA outer membrane proteins; D000242:Cyclic AMP; D005947:Glucose