We observed previously that cisplatin-resistant HeLa cells were cross-resistant to UV light due to accumulation of DDB2, a protein implicated in DNA repair. More recently, we found that cFLIP, which represents an anti-apoptotic protein whose level is induced by DDB2, was implicated in preventing apoptosis induced by deathreceptor signaling. In the present study, we investigated whether DDB2 has a protective role against UV irradiation and whether cFLIP is also involved in this process. Methods: We explored the role of DDB2 in mediating UV resistance in both human cells and Drosophila. To do so, DDB2 was overexpressed by using a full-length. | Sun et al. Journal of Biomedical Science 2010 17 27 http content 17 1 27 a NSC The cost of publication In Journal of Blomodlcal Science Is bome by the National Science Council Taiwan JOURNAL OF BIOMEDICAL SCIENCE RESEARCH Open Access Damaged DNA-binding protein 2 DDB2 protects against UV irradiation in human cells and Drosophila Nian-Kang Sun21 2 Chun-Ling Sun21 Chia-Hua Lin 1 Li-Mai Pai1 and Chuck CKChao 1 Abstract Background We observed previously that cisplatin-resistant HeLa cells were cross-resistant to UV light due to accumulation of DDB2 a protein implicated in DNA repair. More recently we found that cFLIP which represents an anti-apoptotic protein whose level is induced by DDB2 was implicated in preventing apoptosis induced by deathreceptor signaling. In the present study we investigated whether DDB2 has a protective role against UV irradiation and whether cFLIP is also involved in this process. Methods We explored the role of DDB2 in mediating UV resistance in both human cells and Drosophila. To do so DDB2 was overexpressed by using a full-length open reading frame cDNA. Conversely DDB2 and cFLIP were suppressed by using antisense oligonucleotides. Cell survival was measured using a colony forming assay. Apoptosis was monitored by examination of nuclear morphology as well as by flow cytometry and Western blot analyses. A transcription reporter assay was also used to assess transcription of cFLIP Results We first observed that the cFLIP protein was upregulated in UV-resistant HeLa cells. In addition the cFLIP protein could be induced by stable expression of DDB2 in these cells. Notably the anti-apoptotic effect of DDB2 against UV irradiation was largely attenuated by knockdown of cFLIP with antisense oligonucleotides in HeLa cells. Moreover overexpression of DDB2 did not protect against UV in VA13 and XP-A cell lines which both lack cFLIP. Interestingly ectopic expression of human DDB2 in Drosophila dramatically inhibited UV-induced fly .
