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DNA replication - Escherichia coli K-12 MG1655
A complex network of interacting proteins and enzymes is required for DNA replication. Generally, DNA replication follows a multistep enzymatic pathway. At the DNA replication fork, a DNA helicase (DnaB or MCM complex) precedes the DNA synthetic machinery and unwinds the duplex parental DNA in cooperation with the SSB or RPA. On the leading strand, replication occurs continuously in a 5 to 3 direction, whereas on the lagging strand, DNA replication occurs discontinuously by synthesis and joining of short Okazaki fragments. In prokaryotes, the leading strand replication apparatus consists of a DNA polymerase (pol III core), a sliding clamp (beta), and a clamp loader (gamma delta complex). The DNA primase (DnaG) is needed to form RNA primers. Normally, during replication of the lagging-strand DNA template, an RNA primer is removed either by an RNase H or by the 5 to 3 exonuclease activity of DNA pol I, and the DNA ligase joins the Okazaki fragments. In eukaryotes, three DNA polymerases (alpha, delta, and epsilon) have been identified. DNA primase forms a permanent complex with DNA polymerase alpha. PCNA and RFC function as a clamp and a clamp loader. FEN 1 and RNase H1 remove the RNA from the Okazaki fragments and DNA ligase I joins the DNA.
09120 Genetic Information Processing; 09124 Replication and repair
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eco03030  DNA replication

Ortholog table
eco_M00260  DNA polymerase III complex, bacteria [PATH:eco03030]
Escherichia coli K-12 MG1655 [GN:eco]
b1842  holE; DNA polymerase III, theta subunit [KO:K02345] [EC:]
b0215  dnaQ; DNA polymerase III epsilon subunit [KO:K02342] [EC:]
b0184  dnaE; DNA polymerase III alpha subunit [KO:K02337] [EC:]
b0470  dnaX; DNA polymerase III/DNA elongation factor III, tau and gamma subunits [KO:K02343] [EC:]
b1099  holB; DNA polymerase III, delta prime subunit [KO:K02341] [EC:]
b0640  holA; DNA polymerase III, delta subunit [KO:K02340] [EC:]
b4372  holD; DNA polymerase III, psi subunit [KO:K02344] [EC:]
b4259  holC; DNA polymerase III, chi subunit [KO:K02339] [EC:]
b3701  dnaN; DNA polymerase III, beta subunit [KO:K02338] [EC:]
b4052  dnaB; replicative DNA helicase [KO:K02314] [EC:]
b3066  dnaG; DNA primase [KO:K02316] [EC:2.7.7.-]
b4059  ssb; single-stranded DNA-binding protein [KO:K03111]
b0214  rnhA; ribonuclease HI, degrades RNA of DNA-RNA hybrids [KO:K03469] [EC:]
b0183  rnhB; ribonuclease HII, degrades RNA of DNA-RNA hybrids [KO:K03470] [EC:]
b3863  polA; 5' to 3' DNA polymerase and 3' to 5'/5' to 3' exonuclease [KO:K02335] [EC:]
b2411  ligA; DNA ligase, NAD(+)-dependent [KO:K01972] [EC:]
b3647  ligB; DNA ligase, NAD(+)-dependent [KO:K01972] [EC:]
Stillman B.
Smart machines at the DNA replication fork.
Cell 78:725-8 (1994)
Waga S, Stillman B.
The DNA replication fork in eukaryotic cells.
Annu Rev Biochem 67:721-51 (1998)
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