Overexpression of the dnaA gene in Escherichia coli B/r: chromosome and minichromosome replication in the presence of rifampin.
AUTOR(ES)
Pierucci, O
RESUMO
The replication of chromosomes and minichromosomes in Escherichia coli B/r was examined under conditions in which the dnaA gene product was overproduced. Increased levels of the DnaA protein were achieved by thermoinduction of the dnaA gene, under the control of the lambda pL promoter, or by cellular maintenance of multicopy plasmids carrying the dnaA gene under the control of its own promoters. Previous work has shown that overproduction of DnaA protein stimulates replication of the chromosomal origin, oriC, but that the newly initiated forks do not progress along the length of the chromosome (T. Atlung, K. V. Rasmussen, E. Clausen, and F. G. Hansen, p. 282-297, in M. Schaechter, F. C. Neidhardt, J. L. Ingraham, and N. O. Kjeldgaard, ed., The Molecular Biology of Bacterial Growth, 1985). In the present study, it was found that overproduction of DnaA protein caused both a two- to threefold increase in the amount of residual chromosome replication and an extended synthesis of minichromosome DNA in the presence of rifampin. The amount of residual chromosome replication was consistent with the appearance of functional replication forks on the majority of the chromosomes. Since the rate of DNA accumulation and the cellular DNA/mass ratios were not increased significantly by overexpression of the dnaA gene, we concluded that the addition of rifampin either enabled stalled replication forks to proceed beyond oriC or enabled new forks to initiate on both chromosomes and minichromosomes, or both.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=212037Documentos Relacionados
- Initiation of chromosome replication in dnaA and dnaC mutants of Escherichia coli B/r F.
- Kinetics of minichromosome replication in Escherichia coli B/r.
- Expression of accumulated capacity for initiation of chromosome and minichromosome replication in dnaA mutants of Escherichia coli.
- Genetic Analysis of the Leucine Region in Escherichia coli B/r: Gene-Enzyme Assignments
- Chromosome Replication and the Division Cycle of Escherichia coli B/r