DNA repair in man

DNA repair in man can be described in general terms, but details are still obscure. Excision repair of base damage has a general similarity to the mechanism of the bacterial uvr ABC exonuclease, but the individual roles of at least 15 genes that regulate mammalian excision repair are as yet unknown. The differential repair of specific regions of DNA and of specific genes is highlighted by the clustered mode of repair characteristic of xeroderma pigmentosum group C and by the rapid repair of the dihydrofolate reductase gene. Cloning of genes that specify repair in man is proceeding slowly, in part, because of confusion by genes that produce only partial correction or nonspecific changes in sensitivity and by phenotypic reversion. In human cells, DNA damage-inducible genes are recognized that may overlap the spectra of other stress-induced proteins, but the relationship of these to any error-prone or recA-like system is unknown and unlikely. Four diseases, xeroderma pigmentosum, ataxia telangiectasia, Cockayne syndrome, and Fanconi anemia, have well-documented and significantly increased sensitivities to DNA-damaging agents, and each has recognizable though complex abnormalities in processing DNA damage. In addition, a wide variety of diseases and cellular processes have been ascribed to an association with DNA damage and repair, but the accuracy and significance of these associations are hard to identify.