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A double-strand break repair model refers to the various models of pathways that cells undertake to repair double strand-breaks (DSB). DSB repair is an important cellular process, as the accumulation of unrepaired DSB could lead to chromosomal rearrangements, tumorigenesis or even cell death. [ 1 ]
[48] γH2AX (H2AX phosphorylated on serine 139) can be detected as soon as 20 seconds after irradiation of cells (with DNA double-strand break formation), and half maximum accumulation of γH2AX occurs in one minute. [48] The extent of chromatin with phosphorylated γH2AX is about two million base pairs at the site of a DNA double-strand break.
The RecBCD pathway is the main recombination pathway used in many bacteria to repair double-strand breaks in DNA, and the proteins are found in a broad array of bacteria. [63] [64] [65] These double-strand breaks can be caused by UV light and other radiation, as well as chemical mutagens.
Non-homologous end joining (NHEJ) is a pathway that repairs double-strand breaks in DNA. It is called "non-homologous" because the break ends are directly ligated without the need for a homologous template, in contrast to homology directed repair (HDR), which requires a homologous sequence to guide repair.
In mammalian females the period of arrest may last for years. During this period of arrest, oocytes are subject to spontaneous DNA damage including double-strand breaks. However, the oocytes can efficiently repair DNA double-strand breaks, allowing the restoration of genetic integrity and the protection of offspring health. [8]
Bile acids cause DNA damage, including oxidative DNA damage, double-strand DNA breaks, aneuploidy and chromosome breakage. [55] High-normal levels of the bile acid deoxycholic acid cause apoptosis in human colon cells, [ 56 ] but may also lead to colon cancer if repair and apoptotic defenses are insufficient.
A double-strand break is a kind of DNA damage in which both strands in the double helix are severed. DSBs only occur during DNA replication of the cell cycle.Furthermore, DSBs can lead to genome rearrangements and instability. [3]
Recombination, in this model, is initiated by a double-strand break (or gap) shown in the DNA molecule (chromatid) at the top of the figure. Other types of DNA damage may also initiate recombination. For instance, an inter-strand cross-link (caused by exposure to a cross-linking agent such as mitomycin C) can be repaired by HRR.