Enhanced repair of cyclobutane pyrimidine dimers and improved UV resistance in photolyase transgenic mice

Abstract

During evolution, placental mammals appear to have lost cyclobutane pyrimidine dimer (CPD) photolyase, an enzyme that efficiently removes UV-induced CPDs from DNA in a light-dependent manner. As a consequence, they have to rely solely on the more complex, and for this lesion less efficient, nucleotide excision repair pathway. To assess the contribution of poor repair of CPDs to various biological effects of UV, we generated mice expressing a marsupial CPD photolyase transgene. Expression from the ubiquitous beta-actin promoter allowed rapid repair of CPDs in epidermis and dermis. UV-exposed cultured dermal fibroblasts from these mice displayed superior survival when treated with photoreactivating light. Moreover, photoreactivation of CPDs in intact skin dramatically reduced acute UV effects like erythema (sunburn), hyperplasia and apoptosis. Mice expressing the photolyase from keratin 14 promoter photo reactivate CPDs in basal and early differentiating keratinocytes only. Strikingly, in these animals, the anti-apoptotic effect appears to extend to other skin compartments, suggesting the presence of intercellular apoptotic signals. Thus, providing mice with CPD photolyase significantly improves repair and uncovers the biological effects of CPD lesions.

Enhanced DDB2 Expression Protects Mice from Carcinogenic Effects of Chronic UV-B Irradiation

“…van der Horst, Erasmus University Medical Center, Rotterdam, the Netherlands; ref. 27). In the resulting construct (designated pC9648), the human K14 promoter was followed by FLAG-DDB2 fused at the 3V end to exon 2 (the last 22 bp), intron 2, exon 3, and the 3V untranslated region (including the polyadenylation signal) of the human b-globin gene.…”

Differential Role of Basal Keratinocytes in UV-Induced Immunosuppression and Skin Cancer

“…Besides the ability of RNA (20,21) and proteins (5) to absorb light at the UV wavelength, our recent findings have unequivocally pointed to DNA as the biologically most relevant target of UV radiation (12,22,35). UV induces the formation of major dimer configurations, namely the cyclobutane pyrimidine dimers (CPDs) and 6-4 photoproducts (6-4PPs), generated by covalent bonds between two adjacent pyrimidines, that interfere with biological processes (e.g., transcription and replication) critical for cell viability (28).…”

“…To unravel the contribution of the individual classes of photolesions (i.e., CPDs versus 6-4PPs) to the deleterious outcome of UV exposure in the skin, we have previously generated transgenic mice that ubiquitously express either the Potorous tridactylus CPD photolyase (␤-act-CPD-PL) or the Arabidopsis thaliana 6-4PP photolyase (␤-act-6-4PP-PL) from the ␤-actin promoter (35). Light-dependent removal of CPDs and/or 6-4PPs from the skin provided ample evidence that CPDs, rather than 6-4PPs, are mostly responsible for the majority of the adverse effects upon UV exposure, including sunburn, mutagenesis, and skin cancer (21,33).…”

DNA photolyases of Chrysodeixis chalcites nucleopolyhedrovirus are targeted to the nucleus and interact with chromosomes and mitotic spindle structures

“…Pyrimidine dimers can be repaired by several pathways, including photoreactivation (for a review, see Essen & Klar, 2006), nucleotide excision repair (NER) (reviewed by Schul et al, 2002) and base excision repair (reviewed by Kimura et al, 2004). Photoreactivation is the simplest and fastest DNA repair pathway, and uses only visible light as an energy source and involves a single enzyme, either a CPD or a (6-4)PP photolyase.…”