DNA photolyases are enzymes which mediate the light-dependent repair (photoreactivation) of UV-induced damage products in DNA by direct reversal of base damage rather than via excision repair pathways. Arabidopsis thaliana contains two photolyases specific for photoreactivation of either cyclobutane pyrimidine dimers (CPDs) or pyrimidine (6-4)pyrimidones (6-4PPs), the two major UV-B-induced pho...

UV inactivation, photoreactivation, and dark repair of Escherichia coli and Cryptosporidium parvum were investigated with the endonuclease sensitive site (ESS) assay, which can determine UV-induced pyrimidine dimers in the genomic DNA of microorganisms. In a 99.9% inactivation of E. coli, high correlation was observed between the dose of UV irradiation and the number of pyrimidine dimers induce...

A genetic screen for mutants of Arabidopsis that are hypersensitive to UV light was developed and used to isolate a new mutant designated uvhl. UV hypersensitivity in uvhl was due to a single recessive trait that is probably located on chromosome 3. Although isolated as hypersensitive to an acute exposure to UV-C light, uvhl was also hypersensitive to UV-B wavelengths, which are present in sunl...

There is accumulating evidence suggesting that expression of genes for repair of UV damage to DNA in mammals and fish is regulated developmentally. Therefore, the activity of excision repair and photoreactivation in vivo in young larvae of Drosophila melanogaster was examined in a strain carrying the mutation mus201 that was unable to carry out excision repair. The photoreactivation activity in...

Halobacterium is one of the few known Archaea that tolerates high levels of sunlight in its natural environment. Photoreactivation is probably its most important strategy for surviving UV irradiation and we have shown that both of the major UV photoproducts, cyclobutane pyrimidine dimers (CPDs) and (6-4) photoproducts, can be very efficiently repaired by photoreactivation in this organism. Ther...

The uvr mutations of Escherichia coli K-12 decrease the ability of cells to survive ultraviolet light (UV), to excise pyrimidine dimers from their deoxyribonucleic acid and to reactivate bacteriophage exposed to UV. The rec mutations decrease the ability of the cells to survive UV and to undergo genetic recombination. Certain rec mutations, including recA1, rec-12, recA13, and rec-56, are neces...

A sufficient dose of ultraviolet light (2,0537 A) inactivates most microorganisms. Exposure of inactivated cells to suitable visible light results in the recovery of a large portion of the cells from their otherwise fatal ultraviolet-induced injury. The discovery of light-induced recovery (Kelner, 1949) and its confirmation for bacteriophage by Dulbecco (1949) gives us fresh hope for solving th...