A novel regulatory mechanism couples deoxyribonucleotide synthesis and DNA replication in Escherichia coli.
We present evidence for a complex regulatory interplay between the initiation of DNA replication and deoxyribonucleotide synthesis. In Escherichia coli, the ATP-bound DnaA protein initiates chromosomal replication. Upon loading of the beta-clamp subunit (DnaN) of the replicase, DnaA is inactivated as its intrinsic ATPase activity is stimulated by the protein Hda. The beta-subunit acts as a matchmaker between Hda and DnaA. Chain elongation of DNA requires a sufficient supply of deoxyribonucleotides (dNTPs), which are produced by ribonucleotide reductase (RNR). We present evidence suggesting that the molecular switch from ATP-DnaA to ADP-DnaA is a critical step coordinating DNA replication with increased deoxyribonucleotide synthesis. Characterization of dnaA and dnaN mutations that result in a constitutively high expression of RNR reveal this mechanism. We propose that the nucleotide bound state of DnaA regulates the transcription of the genes encoding ribonucleotide reductase (nrdAB). Accordingly, the conversion of ATP-DnaA to ADP-DnaA after initiation and loading of the beta-subunit DnaN would allow increased nrdAB expression, and consequently, coordinated RNR synthesis and DNA replication during the cell cycle.
Department of Microbiology, Harvard Medical School, Boston, MA, USA. gon@ibsm.cnrs-mrs.fr
Stéphanie
S
Gon
Johanna E
JE
Camara
Hege K
HK
Klungsøyr
Elliott
E
Crooke
Kirsten
K
Skarstad
Jon
J
Beckwith
D000244:Adenosine Diphosphate / Q000378:metabolism; D000251:Adenosine Triphosphatases / Q000378:metabolism / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000378:metabolism; D001426:Bacterial Proteins / Q000378:metabolism; D002453:Cell Cycle; D002876:Chromosomes, Bacterial / Q000235:genetics / Q000378:metabolism; D004258:DNA Polymerase III / Q000235:genetics / Q000378:metabolism; D004261:DNA Replication; D004269:DNA, Bacterial / Q000235:genetics* / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D003854:Deoxyribonucleotides / Q000096:biosynthesis*; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology; D005095:Exoribonucleases / Q000235:genetics / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D009154:Mutation / Q000235:genetics; D012264:Ribonucleotide Reductases / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic
D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; D003854:Deoxyribonucleotides; C066312:DnaA protein, Bacteria; D029968:Escherichia coli Proteins; C489683:rnr protein, E coli; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D012264:Ribonucleotide Reductases; C101139:beta subunit, DNA polymerase III; D004258:DNA Polymerase III; D005095:Exoribonucleases; D000251:Adenosine Triphosphatases; C435211:Hda protein, E coli