Temperature- and H-NS-dependent regulation of a plasmid-encoded virulence operon expressing Escherichia coli hemolysin.
Proteins H-NS and Hha form a nucleoprotein complex that modulates expression of the thermoregulated hly operon of Escherichia coli. We have been able to identify two H-NS binding sites in the hly regulatory region. One of them partially overlaps the promoter region (site II), and the other is located about 2 kbp upstream (site I). In contrast, Hha protein did not show any preference for specific sequences. In vitro, temperature influences the affinity of H-NS for a DNA fragment containing both binding sites and H-NS-mediated repression of hly operon transcription. Deletion analysis of the hly regulatory region confirms the relevance of site I for thermoregulation of this operon. We present a model to explain the temperature-modulated repression of the hly operon, based on the experiments reported here and other, preexisting data.
Departament de Microbiologia, Universitat de Barcelona, 08028 Barcelona, Spain.
Cristina
C
Madrid
José M
JM
Nieto
Sònia
S
Paytubi
Maurizio
M
Falconi
Claudio O
CO
Gualerzi
Antonio
A
Juárez
D001426:Bacterial Proteins; D001483:Base Sequence; D001665:Binding Sites; D018983:DNA Footprinting / Q000379:methods; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism / Q000472:pathogenicity*; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial; D006460:Hemolysin Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009876:Operon; D010957:Plasmids / Q000235:genetics*; D017422:Sequence Analysis, DNA; D013696:Temperature; D014158:Transcription, Genetic; D014774:Virulence / Q000235:genetics
D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; C031908:H-NS protein, bacteria; D006460:Hemolysin Proteins