Nucleotide excision repair: ERCC1 and TFIIH complexes

DNA is the carrier of genetic information in living organisms. The information stored in the nucleotide sequence of DNA is transmitted to the offspring by generating identical copies of the parental DNA molecules. Damage in DNA can cause loss of genetic information. Nevertheless, the DNA is continuously subject to alterations, and its instability is likely one of the major factors in mutagenesis. The structure of DNA can be modified spontaneously by hydrolysis, oxidation, or by environmental factors such as ultra-violet (UV) light, X-rays, or numerous chemical agents. Replication of unrepaired DNA can cause genetic changes, which may affect proper functioning of proteins encoded by that DNA. As a result cellular malfunction, onset of carcinogenesis, inborn defects, or even cell death can occur. In addition, DNA damage can interfere with other essential metabolizing processes, like recombination or transcription, with deleterious consequences for the cell. In order to maintain the integrity of DNA, all organisms have evolved a complex network of mechanisms to prevent or repair DNA damage. The different pathways known are able to handle distillct classes of DNA damage.