Autoregulation of the dnaA gene of Escherichia coli K12

Atlung, Tove; Clausen, Erik; Hansen, Flemming

doi:10.1007/bf00425729

Cited by 187 publications

(125 citation statements)

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“…Our current investigation supports this interpretation; purified DnaA protein binds to the dnaA promoter region in vitro. Thus, as in E. coli (2,6,20) and B. subtilis (39), the S. lividans dnaA gene seems to be autoregulated by its own product. However, in P. putida, expression of the dnaA gene is apparently not autoregulated (17).…”

Section: Discussionmentioning

confidence: 85%

Minimal requirements of the Streptomyces lividans 66 oriC region and its transcriptional and translational activities

Zakrzewska‐Czerwińska

Majka

Schrempf

1995

J Bacteriol

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Deletion analysis of a previously constructed minichromosome revealed that a stretch of DNA which is longer than 623 bp but shorter than 837 bp is required for autonomous replication of the Streptomyces lividans chromosome. Each of the dnaA and dnaN genes flanking the oriC region is individually transcribed from two promoters. Within the intergenic, nontranslatable region between the dnaA and dnaN genes, five main transcripts and several less abundant transcripts of various lengths as well as one of the promoters were identified. The introduction of additional DnaA boxes in S. lividans led to a significant increase in dnaA gene transcripts and to an enhanced level of the DnaA (73-kDa) protein. In summary, the data suggest that dnaA gene transcription is autoregulated and that initiation of the S. lividans chromosome is tightly controlled.The replication of several bacterial chromosomes was found to be initiated at the origin of replication, oriC. The features of oriC and, with a few exceptions, the arrangement of genes in its vicinity are remarkably similar among eubacteria (25, 38). Sequence analyses revealed that the origins of various eubacteria contain highly conserved segments which are separated by variable spacer regions. The DnaA box motifs (TTATC/AC AC/AA) (36) constituting the binding sites for the initiator protein DnaA are prominent in the conserved parts of oriC regions from various bacteria. The only relevant variation is an A-to-G exchange at the third position of the DnaA box motif within GC-rich DNA present in gram-positive bacteria such as Micrococcus luteus (10) and Streptomyces lividans (42). Most eubacteria contain a block of genes, dnaA-dnaN-recF-gyrB (10, 38), encoding the initiator protein DnaA, the ␤-subunit of DNA polymerase III holoenzyme, a product for recombination, and the ␤-subunit of DNA gyrase, respectively. Within most bacteria, oriC is situated close to the dnaA gene. In Escherichia coli, the arrangement of the dnaA region matches that in other bacteria; however, this region is located about 42 kb away from oriC (35).Procaryotic chromosomal replication has been best studied in E. coli. Its DnaA protein is a basic protein of 52 kDa to which ATP binds. About 10 to 40 ATP-DnaA molecules interact with four DnaA boxes within oriC (19,36). According to a current model (14), the newly synthesized DnaA protein is titrated by these DnaA boxes. As soon as the number of DnaA molecules exceeds the number of boxes, initiation is supposed to occur. A high number of GATC sites which can be methylated by the Dam methyltransferase have been found in the oriC region of E. coli, as well as in other members of the family Enterobacteriaceae (44), and GANTC sites are present in the Caulobacter crescentus oriC (43).Contrary to many bacteria, Streptomyces species grow as substrate mycelia which differentiate to aerial mycelia and spores upon depletion of nutrients. Depending on the species, the size of the GC-rich Streptomyces chromosome ranges between 6.6 and 8 Mb (18,32). Recently, we identified the...

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Section: Discussionmentioning

confidence: 85%

Minimal requirements of the Streptomyces lividans 66 oriC region and its transcriptional and translational activities

Zakrzewska‐Czerwińska

Majka

Schrempf

1995

J Bacteriol

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“…DnaA did complex with the repA2 promoter probe, probably at the predicted DnaA box 158 bp upstream of the repA2 translational start site. DnaA has been implicated as a transcription factor as it autoregulates dnaA gene expression (Atlung et al, 1985) and either represses or activates expression from several other genes (Messer & Weigel, 1997). Thus the DnaA-binding site upstream of the repA2B2C2 operon may be biologically relevant such that expression of the pSymA genes encoded in the replicator region are transcriptionally coordinated with chromosome replication.…”

Section: Dnaa Binds To Predicted Binding Sites In the Heme-y02793 Intmentioning

confidence: 99%

The Sinorhizobium meliloti chromosomal origin of replication

2006

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The predicted chromosomal origin of replication (oriC) from the alfalfa symbiont Sinorhizobium meliloti is shown to allow autonomous replication of a normally non-replicating plasmid within S. meliloti cells. This is the first chromosomal replication origin to be experimentally localized in the Rhizobiaceae and its location, adjacent to hemE, is the same as for oriC in Caulobacter crescentus, the only experimentally characterized alphaproteobacterial oriC. Using an electrophoretic mobility shift assay and purified S. meliloti DnaA replication initiation protein, binding sites for DnaA were mapped in the S. meliloti oriC region. Mutations in these sites eliminated autonomous replication. S. meliloti that expressed DnaA from a plasmid lac promoter was observed to form pleomorphic filamentous cells, suggesting that cell division was perturbed. Interestingly, this cell phenotype is reminiscent of differentiated bacteroids found inside plant cells in alfalfa root nodules.

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“…A number of experimental observations have led to speculation that DnaA is involved in coupling DNA initiation to the oriC/mass ratio of a cell (2). However, this view of DnaA as the cell cycle oscillator is the subject of an ongoing debate in the literature (8).…”

mentioning

confidence: 99%

Escherichia coli Fis and DnaA proteins bind specifically to the nrd promoter region and affect expression of an nrd-lac fusion

1994

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The Escherichia coli nrd operon contains the genes encoding the two subunits of ribonucleoside diphosphate reductase. The regulation of the nrd operon has been observed to be very complex. The specific binding of two proteins to the nrd regulatory region and expression of mutant nrd-lac fusions that do not bind these proteins are described. A partially purified protein from an E. coli cell extract was previously shown to bind to the promoter region and to regulate transcription of the nrd operon (C. K. Tuggle and J. A. Fuchs, J. Bacteriol. 172:1711-1718, 1990 starved cells. The protein extract from a thymine-starved culture protected several sites in the promoter region from DNase I digestion (47). Here, we report the identity of this protein as the E. coli factor for inversion stimulation (Fis).Fis is an 11.2-kDa protein initially identified by its ability to stimulate Hin-, Gin-, and Cin-mediated DNA inversion (18,23,25). The involvement of Fis in other site-specific recombinations, including excision and integration recombination reactions of bacteriophage X DNA, was also demonstrated (3,4,44). Fis has also been shown to be a transcriptional activator at rRNA and tRNA promoters in E. coli (6,38). In vitro footprinting experiments show protection of specific sites in the E. coli oriC sequence by Fis (17), and examination of DNA synthesis in fis gyrB double mutants indicates a synergistic involvement of Fis and DNA gyrase in the initiation of DNA replication at oriC (14).The fis gene has been cloned, sequenced, and mapped to 72 min on the E. coli chromosome (23,26). The gene encodes an 11,239-Da, 98-amino-acid polypeptide. The fis operon promoter has been located 1 kb upstream of the fis start codon (36), and Fis synthesis is autoregulated. Transcription of fis is controlled as part of the stringent response. A degenerate consensus binding site for Fis has been proposed: (G/T) nnYRnn(A/T)nnYRnn(C/A) (where Y is a pyrimidine, R is a purine, and n is any nucleotide) (22). However, local DNA topology and the ability of the DNA duplex to bend, accommodating the helix-turn-helix DNA-binding domains of the Fis dimer, appear to be more important in determining Fis binding at any given site (51) than the sequence per se. In activating transcription of stable RNA operons in E. coli, binding of Fis to upstream activating sequences lowers the dissociation constant of the RNA polymerase-promoter complex (34).

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Autoregulation of the dnaA gene of Escherichia coli K12

Cited by 187 publications

References 49 publications

Minimal requirements of the Streptomyces lividans 66 oriC region and its transcriptional and translational activities

Minimal requirements of the Streptomyces lividans 66 oriC region and its transcriptional and translational activities

The Sinorhizobium meliloti chromosomal origin of replication

Escherichia coli Fis and DnaA proteins bind specifically to the nrd promoter region and affect expression of an nrd-lac fusion

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