Ingvild Flåtten from Kirsten Skarstad's group at the Department of Molecular Cell Biology at the Institute for Cancer Research is first author on an article recently published in "PLOS Genetics" (journal impact factor 8.2). In this paper they demonstrate the DnaA protein is not the limiting factor for initiation of replication in Escherichia coli.
The authors summarize the findings:
Cell cycle regulation of the bacterium Escherichia coli has been studied for many years and its understanding is complicated by the fact that overlapping replication cycles occur during growth in rich media. Under such conditions cells initiate several copies of the chromosome. The active form of the CDC6-like DnaA protein is required for initiation of synchronous and well timed replication cycles and is in a sense the motor of the cell cycle machine. It has long been debated whether it is the accumulation of enough ATP-DnaA that triggers initiation and determines the replication frequency. We have in this work constructed a strain where the “accumulation of ATP-DnaA triggers initiation” model could be tested. Our results suggest that although ATP-DnaA is the main actor in initiation of replication, its accumulation does not control the time of initiation and that the current model requires some modification. We suggest that cell cycle regulation in E. coli has similarities to that of eukaryotes in that origins are “licenced” to initiate by a cell cycle motor and that the precise timing depends signaling from other factors.
Flåtten I, Fossum-Raunehaug S, Taipale R, Martinsen S, Skarstad K (2015)
The DnaA Protein Is Not the Limiting Factor for Initiation of Replication in Escherichia coli
PLoS Genet, 11 (6), e1005276