THE COUPLING BETWEEN FTSZ TRANSCRIPTION AND INITIATION OF DNA-REPLICATION IS NOT MEDIATED BY THE DNAA-BOXES UPSTREAM OF FTSZ OR BY DNAA

The DnaA protein of Escherichia coli is a multifunctional protein whic h, in addition to promoting initiation of replication, can regulate th e initiation or termination of transcription of a variety of genes. It acts by binding to DNA at a defined sequence, termed a DnaA-box. Thre e candidate DnaA-boxes which occur within the essential cell-division genes, ftsQ and ftsA, have been hypothesized to mediate the response o f the downstream ftsZ gene to intracellular levels of DnaA, and thus t o couple the processes of initiation and cell division. We show here t hat, although transcription from promoters upstream of ftsZ is increas ed when initiation of chromosome replication is blocked by DnaA inacti vation, this response is not mediated by the DnaA-boxes near these pro moters, nor is it specific to DnaA. We show, furthermore, that mutatio nal inactivation of the putative DnaA-binding sites in the fts region of the chromosome does not lead to impaired growth or reduced survival of cells.