MODULATED EXPRESSION OF PROMOTERS CONTAINING UPSTREAM CURVED DNA-SEQUENCES BY THE ESCHERICHIA-COLI NUCLEOID PROTEIN H-NS

Replacement of the CRP-binding site of the gal control region by curve d sequences can lead to the restoration of promoter strength in vivo. One curved sequence balled 5A6A, however, failed to do so. The gene hn s exerts a strong negative control on the resulting 5A6A gal promoter as well as on the distant bla promoter, specifically in a 5A6A gal con text. The product of this gene, H-NS, displays a better affinity far t his particular insert compared to other curved sequences. Mechanisms b y which H-NS may repress promoters both at short and long distances fr om a favoured binding site. are discussed.