Light-induced repair

The light-induced repair of cylobutane-type dimers by the enzyme photolyase is of major biological importance. This proceeds by ET from a flavin, and using a model system it has been shown that the electron is likely to be funneled through the DNA base stack (SchwOgler et al. 2000). 

Four major pathways for DNA repair exist that can be subdivided into two classes light-induced repair (photoreactivation) and light-independent repair (dark repair). The latter can be accomplished by three distinct mechanisms ... 

Model compounds in the study of repair of UV-light-induced DNA lesions 98EJ01245. 

Electron donation to nucleobases is a fundamental process exploited by nature to achieve the efficient repair of UV induced lesions in DNA [27, 28]. Nature developed to this end two enzymes, CPD photolyases and (6-4) photolyases, which both inject electrons into the UV damaged DNA bases [29, 30]. Both enzymes are, in many species, including plants, essential for the repair of the UV-light induced DNA lesions depicted in Scheme 1 [31]. 

Ultraviolet light induces the formation of dimers between adjacent thymines in DNA (also occasionally between other adjacent pyrimidines). The formation of thymine dimers interferes with DNA rephcation and normal gene expression. Thymine dimers are eliminated from DNA by a nucleotide excision-repair mechanism (Figure 1-2-4). 

Figure 6.46 Representation of two mechanisms of repair of DNA damage such as ultraviolet light-induced dimerization. The upper line represents cut and patch repair, the lower sister-strand exchange. Thick lines represent newly synthesized DNA. Source From Ref. 12.

Direct Repair Several types of damage are repaired without removing a base or nucleotide. The best-characterized example is direct photoreactivation of cyclobutane pyrimidine dimers, a reaction promoted by DNA photolyases. Pyrimidine dimers result from an ultraviolet light-induced reaction, and photolyases use energy derived from absorbed light to reverse the dam-... 

In bacteria, flavin adenine dinucleotide (FAD) is the prosthetic group of the photolyases that catalyze reductive repair of light-induced pyrimidine dimers in DNA. Riboflavin is the light-emitting molecule in some bioluminescent fungi and bacteria, and is the precursor for synthesis of the dimethylbenzimidazole ring of vitamin B12 (Section 10.7.3). 

N. Uchida, H. Mitani, A. Shima (1995). Multiple effects of fluorescent light on repair of ultraviolet-B-induced DNA lesions in cultured goldfish cells. Photochem. Photobiol., 61,79-83. 

Blagoev, K.B., Alexandrov, B.S., Goodwin, E.H., and Bishop, A.R. (2006) Ultra-violet light induced changes in DNA dynamics may enhance TT-dimer recognition. DNA Repair, 5, 863-867. 

Which of the following enzymes or processes can be involved in repairing DNA in E. coli damaged by UV-light-induced formation of a thymine dimer ... 

Averbeck, D., Papadopoulo, D., and Moustacchi E., Repair of 4,5, 8-trimethylpsoralen plus light-induced DNA damage in normal andFanconi s anemia cell lines. Cancer Res., 48, 2015, 1988. 

The most well-known form of ultraviolet light—induced base damage is the pyrimidine dimer. Although the hallmark repair system for this type of... 

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