Hfq (HF1) stimulates ompA mRNA decay by interfering with ribosome binding.
The adaptation of mRNA stability to environmental changes is a means of cells to adjust the level of gene expression. The Escherichia coli ompA mRNA has served as one of the paradigms for regulated mRNA decay in prokaryotes. The stability of the transcript is known to be correlated inversely with the bacterial growth rate. Thus, the regulation of ompA mRNA stability meets the physiological needs to adjust the level of ompA expression to the rate of cell division. Recently, host factor I (Hfq/HF1) was shown to be involved in the regulation of ompA mRNA stability under slow growth conditions. Here, we present the first direct demonstration that 30S ribosomes bound to the ompA 5'-UTR protect the transcript from RNase E cleavage in vitro. However, the 30S protection was found to be abrogated in the presence of Hfq. Toeprinting and in vitro translation assays revealed that translation of ompA is repressed in the presence of Hfq. These in vitro studies are corroborated by in vivo expression studies demonstrating that the reduced synthesis rate of OmpA effected by Hfq results in functional inactivation of the ompA mRNA. The data are discussed in terms of a model wherein Hfq regulates the stability of ompA mRNA by competing with 30S ribosomes for binding to the ompA 5'-UTR.
Vytvytska
O
O
Institute of Microbiology and Genetics, Vienna Biocenter, 1030 Vienna, Austria.
Moll
I
I
Kaberdin
V R
VR
von Gabain
A
A
Bläsi
U
U
D020121:5' Untranslated Regions / Q000235:genetics; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics*; D001483:Base Sequence; D001665:Binding Sites; D002352:Carrier Proteins / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D029968:Escherichia coli Proteins; D015964:Gene Expression Regulation, Bacterial; D035001:Host Factor 1 Protein; D034982:Integration Host Factors; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D014176:Protein Biosynthesis; D012329:RNA, Bacterial / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000378:metabolism*; D012270:Ribosomes / Q000378:metabolism*
D020121:5' Untranslated Regions; D001425:Bacterial Outer Membrane Proteins; D002352:Carrier Proteins; D029968:Escherichia coli Proteins; D035001:Host Factor 1 Protein; D034982:Integration Host Factors; D012329:RNA, Bacterial; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; C440502:integration host factor, E coli; C078167:OMPA outer membrane proteins