title: Bacterial origin recognition complexes direct assembly of higher-order DnaA oligomeric structures.
abstract: Eukaryotic initiator proteins form origin recognition complexes (ORCs) that bind to replication origins during most of the cell cycle and direct assembly of prereplication complexes (pre-RCs) before the onset of S phase. In the eubacterium Escherichia coli, there is a temporally similar nucleoprotein complex comprising the initiator protein DnaA bound to three high-affinity recognition sites in the unique origin of replication, oriC. At the time of initiation, this high-affinity DnaA-oriC complex (the bacterial ORC) accumulates additional DnaA that interacts with lower-affinity sites in oriC, forming a pre-RC. In this paper, we investigate the functional role of the bacterial ORC and examine whether it mediates low-affinity DnaA-oriC interactions during pre-RC assembly. We report that E. coli ORC is essential for DnaA occupation of low-affinity sites. The assistance given by ORC is directed primarily to proximal weak sites and requires oligomerization-proficient DnaA. We propose that in bacteria, DnaA oligomers of limited length and stability emerge from single high-affinity sites and extend toward weak sites to facilitate their loading as a key stage of prokaryotic pre-RC assembly.
authors.affiliation: Department of Biological Sciences, Florida Institute of Technology, 150 West University Boulevard, Melbourne, FL 32901, USA.
authors.forename: Diana T
authors.initials: DT
authors.lastname: Miller
authors.forename: Julia E
authors.initials: JE
authors.lastname: Grimwade
authors.forename: Thu
authors.initials: T
authors.lastname: Betteridge
authors.forename: Tania
authors.initials: T
authors.lastname: Rozgaja
authors.forename: Julien J-C
authors.initials: JJ
authors.lastname: Torgue
authors.forename: Alan C
authors.initials: AC
authors.lastname: Leonard
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism*; D001483:Base Sequence; D001665:Binding Sites; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000378:metabolism*; D004926:Escherichia coli / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D051738:Origin Recognition Complex / Q000378:metabolism*; D011485:Protein Binding; D020836:Protein Structure, Quaternary; D018741:Replication Origin / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; C066312:DnaA protein, Bacteria; D051738:Origin Recognition Complex