7177-16-18P AID: 2112 | 17/05/2013
RID: 2498 | 14/06/2013Nonhomologous end joining is a repair mechanism occurs in higher eukaryotes. When double-strand breaks occur the broken ends are put back together by a rather inelegant but important mechanism called nonhomologous end joining (NHEJ). The first step is the recognition of the damage.
The NHEJ pathway is initiated when two very abundant proteins KU70 and KU80, bind to the broken ends, forming a heterodimer that serves two functions.
First, it prevents further damage to the ends. Nonhomologous end joining is error prone as some sequence may be lost in the repair process. The consequences of imperfect repair may be far less harmful than leaving the lesion unrepaired.
Presumably this repair pathway evolved because, unless repaired, the broken ends can degrade further, leading to loss of more genetic information.
Secondly it recruits other proteins that trim the strand ends to generate the 5' of P and 3' of –OH ends that are required for ligation.
These lesions can initiate potentially harmful chromosomal rearrangements that could lead to cell death.