A novel transcript for DNA repair gene Ercc1 in mouse skin.

The nucleotide excision repair pathway deals with UV-induced DNA damage. The tissue that receives by far the greatest exposure to UV is the skin and we have investigated the possibility that expression of the nucleotide excision repair gene, Ercc1, may display different properties in the skin to deal with a more demanding role in that tissue. ERCC1, in a complex with XPF, is the structure--specific endonuclease responsible for incising 5' to the UV-induced lesion. We identified a novel Ercc1 mRNA in mouse skin that originates from an alternative upstream promoter. Levels of this skin-specific transcript were low in embryonic skin and increased rapidly after birth, but there was no induction by UV, either in adult skin, or in a cultured keratinocyte model. Levels of the skin-specific Ercc1 transcript were higher in albino than pigmented mouse strains, but there was no difference in ERCC1 protein levels and the expression of the skin-specific transcript was found to be determined by the Ercc1 gene sequence rather than by coat pigmentation. Using an Ercc1 transgene the promoter for the skin-specific transcript was mapped to a region around 400 bp upstream of the normal promoter, where a transposable element with known promoter activity was found in albino but not in pigmented strains.