The Escherichia Coli DatA Suppressor Mutants And Cell Cycle

The datA region is a negative regulatory element for initiation of replication and cell division in Escherichia coli. It is a high affinity binding site for the initiator protein, DnaA. The datA site affects initiation of replication and cell division by decreasing the availability of DnaA. High dose of datA inhibits the growth of a wild type cell, but the mechanism behind is not clear yet. To be able to understand the function of datA in cell cycle, we screened for datA suppressor mutants and found that purL,glgX,xapR and pcnB mutants were datA suppressors. For simplicity, these datA suppressor mutants were named datAS mutant.To understand how datAS mutant suppresses high dose of datA, the cell cycle parameters of datAS mutant of purL, xapR, glgX and pcnB were investigated. The growth rate of the datAS mutants on different media was measured. To see the interaction between DnaA and datAS mutants, double mutants of dnaATS purL,dnaATS glgX,dnaATS xapR and dnaATS pcnB were constructed. Subsequently, the temperature sensitivity of the double mutants was measured. We have found that:1) in the presence of high dosage of datA, the datAS mutants grow on different media; presence of extra datA or deletion of datA does not affect the growth rate of datAS mutants; 2) the purL and glgX cells need purine and sugar respectively; 3) the purL, pcnB, xapR and glgX cells have wildtype replication pattern, and the DnaA concentration in the mutants does not change; 4) datAS mutants grow slowly compared to the wild type cell; 5) the datAS mutants increases temperature sensitivity of dnaA46,dnaA204,dnaA508. The reason why datAS can suppress high dose of datA was discussed briefly.