Bacterial origin recognition complexes direct assembly of higher-order DnaA oligomeric structures.
- Publication Type:
- Journal Article
- Citation:
- Proc Natl Acad Sci U S A, 2009, 106 (44), pp. 18479 - 18484
- Issue Date:
- 2009-11-03
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| Filename | Description | Size | |||
|---|---|---|---|---|---|
 | 2008008310OK.pdf | 1.17 MB |
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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.
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