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In molecular biology, [1] [2] [3] DNA replication is the biological process of producing two identical replicas of DNA from one original DNA molecule. [4] DNA replication occurs in all living organisms acting as the most essential part of biological inheritance.
Initiation of eukaryotic DNA replication is the first stage of DNA synthesis where the DNA double helix is unwound and an initial priming event by DNA polymerase α occurs on the leading strand. The priming event on the lagging strand establishes a replication fork.
More than five decades ago, Jacob, Brenner, and Cuzin proposed the replicon hypothesis to explain the regulation of chromosomal DNA synthesis in E. coli. [18] The model postulates that a diffusible, trans-acting factor, a so-called initiator, interacts with a cis-acting DNA element, the replicator, to promote replication onset at a nearby origin.
The DNA re-replication response is different from the response taken when damage is due to oxygen radical generation. Damage from oxygen radical generations leads to a response from the Myc oncogene, which phosphorylates p53 and H2AX. [16] The ATM/ATR DNA damage network will also respond to cases where there is an overexpression of Cdt1.
Since new DNA must be packaged into nucleosomes to function properly, synthesis of canonical (non-variant) histone proteins occurs alongside DNA replication. During early S-phase, the cyclin E-Cdk2 complex phosphorylates NPAT , a nuclear coactivator of histone transcription. [ 6 ]
A DNA unwinding element (DUE or DNAUE) is the initiation site for the opening of the double helix structure of the DNA at the origin of replication for DNA synthesis. [1] It is A-T rich and denatures easily due to its low helical stability, [ 2 ] which allows the single-strand region to be recognized by origin recognition complex .
Once a cellular division occurs, the pre-RC must revert back to the bORC to ensure that only one round of DNA replication occurs during division. In E. coli, there are 11 GATC sites in the oriC that undergo hemimethylation during DNA replication. The protein SeqA binds to these sites preventing remethylation and blocking the binding of DnaA to ...
DNA is read in the 3' → 5' direction, therefore, nucleotides are synthesized (or attached to the template strand) in the 5' → 3' direction. However, one of the parent strands of DNA is 3' → 5' while the other is 5' → 3'. To solve this, replication occurs in opposite directions.