Disease relevance of oriC

• Versatile use of oriC plasmids for functional genomics of Mycoplasma capricolum subsp. capricolum [1].
• In E. coli, replication initiates at a genetically unique origin, oriC [2].
• A protein that stimulates the enzymatic replication of duplex DNAs of recombinant phages and plasmids bearing the Escherichia coli origin of replication (oriC) has been isolated from an extract of E. coli [3].
• From a comparison of this sequence with oriC sequences of five enteric bacteria, we derived a consensus sequence of bacterial origins that function in E. coli [4].
• The chromosomal replication origin (oriC) of Vibrio harveyi has been isolated on a plasmid and shown to function as an origin in Escherichia coli [4].

High impact information on oriC

• Initiation is promoted by full methylation of GATC sites clustered in oriC; sequestration is specific to the hemimethylated forms generated by replication [5].
• At a ratio of 10-20 monomers per oriC plasmid, the binding blocks initiation by preventing the opening of the 13-mer region by dnaA protein [6].
• A particular outer membrane fraction previously defined as possessing specific affinity for the hemimethylated form of the origin of replication of the E. coli chromosome (oriC) is shown to inhibit the initiation of DNA synthesis at this site on hemimethylated DNA templates in vitro [7].
• The E. coli cell surface specifically prevents the initiation of DNA replication at oriC on hemimethylated DNA templates [7].
• The key inactivation step appears to be membrane inhibition of DnaA initiator protein binding to oriC [7].

Chemical compound and disease context of oriC

• A 16 bp BgI II fragment was deleted in vitro from the minimal origin of replication of the Escherichia coli chromosome, oriC, and was replaced by a 10 kb R1 miniplasmid, pKN1562, containing the basic R1 replicon and a kanamycin resistance gene [8].
• The replication of both ColE1-type plasmids and plasmids bearing the origin of replication of the Escherichia coli chromosome (oriC) has been shown to be inhibited by hemimethylation of adenine residues within GATC sequences [9].
• Among the phospholipids in E. coli membrane, cardiolipin showed the strongest inhibition of DnaA binding to oriC [10].
• Cyclothialidine also inhibited the in vitro DNA replication directed from oriC of E. coli [11].
• A DnaA protein, K178T, in which the central lysine was changed to the smaller amino acid threonine, was able to initiate DNA replication from P1 oriR, but was unable to initiate replication from E. coli oriC or F oriS in vivo [12].

Biological context of oriC

• Hda-deficient cells were very sensitive to variations in the cellular level of DnaA, and DnaA overproduction led to uncontrolled initiation of replication from oriC, causing severe growth retardation or cell death [13].
• Our results suggest that the selection of the infrequent events of homologous recombination could be enhanced by the use of oriC plasmids derived from related mollicute species [1].
• To examine whether methylation of the GATC sites present in the dnaA promoter region is responsible for the strict temporal coordination of initiation events at oriC as measured by the synchrony of initiation, we introduced point mutations eliminating three (TGW1) and five (TGW2) of the six GATC sites present in the dnaA promoter region [14].
• In this study, oriC plasmids were evaluated in M. capricolum subsp. capricolum as genetic tools for (i) expression of heterologous proteins and (ii) gene inactivation by homologous recombination [1].
• Loss of the integrated plasmid results in a temperature- and rich-medium-sensitive strain that replicates the chromosome from oriC and oriX [15].

Anatomical context of oriC

• The binding of hemimethylated oriC to Escherichia coli membranes has been implicated in the prevention of premature reinitiation at newly replicated chromosomal origins in a reaction that involves the SeqA protein [16].
• In the case of oriC plasmids, this inhibition was previously shown to be mediated by the specific affinity of the hemimethylated origin DNA for an outer cell membrane fraction [9].

Associations of oriC with chemical compounds

• Similar periodic formation of the oriC complex was also observed when DNA elongation was inhibited by addition of nalidixic acid to the culture [17].
• Guanine at position 3 determines DnaA-ATP preference, and changing this base to thymine at both I sites allows DnaA-ADP to bind and open oriC, although DNA strand separation is not precisely localized in the AT-rich region [18].
• It is essentially the same as that described for the replication of oriC plasmid DNA [Fuller, R.S., Kaguni, J.M. & Kornberg, A. (1981) Proc. Natl. Acad. Sci. USA 78, 7370-7374] [19].
• Cardiolipin binding of nucleotide-free dnaA protein prevents binding of ATP and initiation of oriC replication [20].
• Because a region near the N terminus of DnaA is required for self-oligomerization and the loading of DnaB helicase at oriC, we asked if these functions are separable or interdependent by substituting many conserved amino acids in this region with alanine to identify essential residues [21].

Physical interactions of oriC

• Hemi-methylated oriC DNA binding activity found in non-specific acid phosphatase [22].

Other interactions of oriC

• This interaction stimulates DnaA protein binding to the chromosome replication origin (oriC) and the mioC promoter region, protects DnaA protein from thermal inactivation, releases ADP but not ATP bound to DnaA protein, and restores normal DNA replication activity and ATPase activity in inactive ADP-DnaA protein preparations [23].
• Overexpression of mutant forms of MreB inhibited cell division, caused abnormal MreB filament morphology and induced severe localization defects of the nucleoid and of the oriC and terC chromosomal regions [24].
• The Escherichia coli DNA replication origin (oriC) and the adjacent asparagine synthetase gene (asnA) have been inserted into the duplex replicative form DNA of the single-stranded phage vector M13Goril [25].
• Site specific binding to hemimethylated oriC, of the heavy density membrane obtained from seqA mutant, could be restored by addition of a low amount of His-tagged SeqA protein [26].
• The oriC origin of replication from p beta 5 was replaced by the rep origin from pSC101 and named p beta 6 [27].

Analytical, diagnostic and therapeutic context of oriC

• Integration of mini-R1 into oriC was verified by Southern blotting and by analysis of the R1 incompatibility phenotype [8].
• Electron microscopy has shown that plasmid replication begins at or near oriC from which it progresses bidirectionally to completion [28].
• Using DNase footprinting and surface plasmon resonance we show that binding to ATP-DnaA boxes in the AT-rich region of oriC of E.coli requires binding to the 9mer DnaA box R1 [29].
• We find that interaction of DnaA protein with oriC DNA is needed to stabilize DnaA protein during this rejuvenation process [30].
• Mutations in the left half of oriC, in DnaA boxes M, R2 or R3 or in the Fis or IHF binding sites caused moderate asynchrony of the initiation of chromosome replication, as measured by flow cytometry [31].

References