DnaA Protein Regulates Expression Of The UvrB And GyrA Gene In E.Coli

Escherichia coli has been widely used in the research fields of mol-ecular biology, biochemistry and genetics as a model organism of a sing-le cell. Better understanding of the E. coli cellular processes including DNA replication, cell cycle control and gene expression will shed light on the regulation of cell cycle of both normal and cancer cells. DnaA is also a transcription factor, regulating the expression of dnaA、mioC and the nrdAB gene or operon through binding to DnaA-box in the promoter regi-on of these genes.In this study, in order to understand the role of DnaA in the regulation of the E. coli cell cycle, we investigated the regulatory effects of DnaA on the expression of uvrB, gyrA and seqA gene. The lacZ reporter gene was inserted into the downstream of the uvrB, gyrA and seqA gene on chromosome by using one-step inactivation, resulting in the generation of WRH37、WRH28and WRH10E.Coli strain. Additionally, the seqAp, gyrAp, uvrBp3and uvrBp1-3promoters were respectively inserted into the front of lacZ gene on pTAC3953vecter.Under different DnaA conditions, the gene expression of uvrB, gyrA and seqA was measured through β-galactosidase activity using Miller method.The results show that DnaA345mutant protein or datA plasmid derepresses the expression of uvrB gene, but excess DnaA represses the expression, indicating that DnaA regulates uvrB gene expression. Interestingly, the promoter activity of uvrBpl-2containing LexA binding site was much more active compared to the uvrBp3in the dnaA345mutant. DnaA345protein increased the gyrA expression, suggesting that DnaA may be involved in the control of the gyrA expression. However, DnaA do not affect the expression of the seqA gene.