Loss of Hda activity stimulates replication initiation from I-box, but not R4 mutant origins in Escherichia coli

Leise Riber, Kazuyuki Fujimitsu, Tsutomu Katayama, Anders Løbner-Olesen

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

Initiation of chromosome replication in Escherichia coli is limited by the initiator protein DnaA associated with ATP. Within the replication origin, binding sites for DnaA associated with ATP or ADP (R boxes) and the DnaA(ATP) specific sites (I-boxes, tau-boxes and 6-mer sites) are found. We analysed chromosome replication of cells carrying mutations in conserved regions of oriC. Cells carrying mutations in DnaA-boxes I2, I3, R2, R3 and R5 as well as FIS and IHF binding sites resembled wild-type cells with respect to origin concentration. Initiation of replication in these mutants occurred in synchrony or with slight asynchrony only. Furthermore, lack of Hda stimulated initiation in all these mutants. The DnaA(ATP) containing complex that leads to initiation can therefore be formed in the absence of several of the origin DnaA binding sites including both DnaA(ATP) specific I-boxes. However, competition between I-box mutant and wild-type origins, revealed a positive role of I-boxes on initiation. On the other hand, mutations affecting DnaA-box R4 were found to be compromised for initiation and could not be augmented by an increase in cellular DnaA(ATP)/DnaA(ADP) ratio. Compared with the sites tested here, R4 therefore seems to contribute to initiation most critically.
Original languageEnglish
JournalMolecular Microbiology
Volume71
Issue number1
Pages (from-to)107-122
ISSN0950-382X
Publication statusPublished - 2009
Externally publishedYes

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