TRANSCRIPTIONAL ACTIVATION OF ORI-LAMBDA REGULATES LAMBDA-PLASMID REPLICATION IN AMINO ACID-STARVED ESCHERICHIA-COLI-CELLS

Replication of lambda plasmid DNA is inhibited in amino acid-starved w ild type Escherichia coli cells (i.e., during the stringent response), whereas it proceeds for several hours in relA mutants (i.e., during t he relaxed response). It was demonstrated previously that ppGpp-mediat ed inhibition of transcription starting from the p(R) promoter is resp onsible for inhibition of lambda plasmid replication; RNA polymerase f unction is indispensable for replication of lambda plasmid DNA during the relaxed response. The replication is carried out by the heritable replication complex containing the lambda O protein which is protected from proteases by other elements of this complex. Here we demonstrate that the replication is dependent on DnaG (primase) function. Thus, i n amino acid-starved cells, lambda plasmid replication requires RNA po lymerase function only for transcriptional activation of ori lambda. W e also present evidences that the replication is dependent on the func tion of DNA gyrase. On the basis of these findings and other recent re ports, we demonstrate a model of the regulation of lambda plasmid repl ication driven by the inherited replication complex. It seems that tra nscriptional activation of ori lambda indirectly triggers the initiati on of lambda plasmid DNA replication at least during the relaxed respo nse. (C) 1995 Academic Press, Inc.