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Aphidicolin is a reversible inhibitor of eukaryotic nuclear DNA replication. It blocks the cell cycle at early S phase. It is a specific inhibitor of DNA polymerase Alpha and Delta in eukaryotic cells and in some viruses (vaccinia [1] [2] and herpesviruses) and an apoptosis inducer in HeLa cells.
In some experiments, a researcher may want to control and synchronize the time when a group of cells progress to the next phase of the cell cycle. [5] The cells can be induced to arrest as they arrive (at different time points) at a certain phase, so that when the arrest is lifted (for instance, rescuing cell cycle progression by introducing another chemical) all the cells resume cell cycle ...
Similar to S Phase, G2 experiences a DNA damage checkpoint. The cell is once more examined for sites of DNA damage or incomplete replication, and the kinases ATR and ATM are recruited to damage sites. Activation of Chk1 and Chk2 also transpire, as well as p53 activation, to induce cell cycle arrest and halt progression into mitosis.
DNA damage checkpoint is a signal transduction pathway that blocks cell cycle progression in G1, G2 and metaphase and slows down the rate of S phase progression when DNA is damaged. It leads to a pause in cell cycle allowing the cell time to repair the damage before continuing to divide.
An arsenal of DNA repair mechanisms exists to repair various forms of damaged DNA and minimize genomic instability. Most DNA repair mechanisms require an intact DNA strand as template to fix the damaged strand. DNA damage prevents the normal enzymatic synthesis of DNA by the replication fork.
In the presence of DNA damage or replication stress (UV light, methyl methanesulfonate, hydroxyurea or aphidicolin), the POLD4/p12 subunit is rapidly degraded. The catalytic activities of p125 are different whether it is in the heterotetramer (Polδ4, with p12 [ 67 ] [ 68 ] ) or in the heterotrimer (Polδ3, without p12). [ 69 ]
RFC5 and RCF2 are also engaged in DNA damage checkpoints and DNA replication checkpoints. Replication factor C is an emergency backup factor for DNA polymerases. RFC2 gene product required for a cell cycle checkpoint. [4] RFC is a heteropentamer in budding yeast, it is encoded either by RFC1 and RFC2-5 genes.
ATR is a serine/threonine-specific protein kinase that is involved in sensing DNA damage and activating the DNA damage checkpoint, leading to cell cycle arrest in eukaryotes. [8] ATR is activated in response to persistent single-stranded DNA, which is a common intermediate formed during DNA damage detection and repair.