Decreased Levels of (6–4) Photoproduct Excision Repair in Hybrid Fish of the Genus Xiphophorus


  • Posted on the website on 29 March 2004

*To whom correspondence should be addressed: Department of Carcinogenesis, The University of Texas M.D. Anderson Cancer Center, P.O. Box 389, Smithville, TX 78957, USA. Fax: 512-237-2437; e-mail:


Selected hybridization in the fish genus Xiphophorus has been used for many years to study the genetics of malignant melanoma. Because DNA damage caused by ultraviolet radiation is implicated in the etiology of sunlight-induced melanoma, the heritability of mechanisms that mitigate DNA damage is a matter of some interest. We examined nucleotide excision repair of the two major types of DNA-damage induced by sunlight; the cyclobutane pyrimidine dimer (CPD) and the pyrimidine (6–4) pyrimidone dimer [(6–4)PD]. In most cases, removal of the (6–4) PD was more rapid than the CPD, and in many cases, the F1 hybrid showed reduced repair efficiency compared with the parental species. These data demonstrate reduced function in multienzyme hybrid systems and provide molecular support for potential reduced fitness in hybrid fish under conditions of environmental stress.