CONSERVED UPSTREAM REGULATORY ELEMENTS IN THE LEADER OF TRANSMISSION PLASMID R46

Nucleotide sequences of six highly homologous (94%) conserved upstream (CUP) repeats of the leader (14 kb) of an IncN transmission plasmid R 46 were analyzed comparatively. The full-length CUP element is of abou t 400 nt and includes two regions differing in the GC content (74% and 40%). Five CUP elements are similarly associated with the 5' regions of open reading frames (ORF) potentially able to code for unrelated pr oteins. The ORF-proximal region of CUP elements is AT-rich and contain s a potent promoter negatively regulated by regulatory proteins ArdK a nd ArdR. The CUP elements were assumed to form an integral regulatory system that controls coordinated expression of ard and other genes ess ential to conjugal transfer of the plasmid and its adaptation to the n ew host.