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Timing of E. coli pre‐RC assembly is determined by two different growth rate‐specific mechanisms
Author(s) -
Leonard Alan C,
Torgue Julien JC,
Miller Diana T,
Grimwade Julia E
Publication year - 2007
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.21.5.a658
Subject(s) - dnaa , dna , helicase , microbiology and biotechnology , dna replication , chemistry , biophysics , biology , origin of replication , biochemistry , gene , rna
New rounds of DNA synthesis require tightly regulated conversion of pre‐existing origin recognition complexes (ORC) into pre‐replication complexes (pre‐RC) that unwind origin DNA and load DNA replicative helicase. Using DNA footprint analysis we find that two mechanisms regulating pre‐RC assembly in E. coli are growth rate‐specific. One mechanism, active only when E. coli contains multiple oriC copies during rapid growth, consists of an ORC‐binding protein (Fis) that increases the number of initiator DnaA copies required to assemble functional pre‐RC. During slow growth with one chromosomal origin, an alternate mechanism (initiator titration) becomes active. DnaA recognition sites within the downstream titration locus ( datA ) become available to compete with oriC for newly synthesized DnaA. By implementing these growth‐rate‐specific switches, E. coli ensures sufficient DnaA (origin overloading) to trigger synchronous DNA synthesis from multiple origins, but makes just enough DnaA available for proper cell cycle timing when only one copy is present. We propose that switches of this type are likely to be common in cells that are capable of both rapid and slow growth over a wide range of nutritional conditions. Supported by NIH GM54052.