INTERACTION OF THE ESCHERICHIA-COLI DNAA PROTEIN WITH BACTERIOPHAGE-LAMBDA DNA

Interaction of the Escherichia coli DnaA (replication initiator) prote in with restriction fragments of phage lambda DNA demonstrated differe ntial binding of DnaA along the whole lambda DNA. Interaction of DnaA with the lambda replication region (from the promoter p(R) to the orig in of replication, ori lambda) demonstrated a strong binding of DnaA t o the region around the p(o) promoter where synthesis of a short antis ense oop RNA is initiated. The four sequences protected by DnaA (two 9 mers and two 5mers) are not related even to a relaxed DnaA box. The pa ttern of protection of these four sequences and the location of three DNase I hypersensitive sites in the lambda, DNA r strand, together wit h results of mobility shift assays and electron microscopy studies, ma y indicate an interaction involving DnaA monomers bound to different D NA positions on one side of the helix and the formation of higher-orde r nucleoprotein structures. Therefore, it is tempting to suggest that DnaA, in addition to its activity in regulation of replication and tra nscription, could be considered as a factor which structures certain c hromosomal regions.