STANDARD_NAME SIMBULAN_UV_RESPONSE_IMMORTALIZED_DN SYSTEMATIC_NAME M3732 COLLECTION C2:CGP MSIGDB_URL https://www.gsea-msigdb.org/gsea/msigdb/human/geneset/SIMBULAN_UV_RESPONSE_IMMORTALIZED_DN NAMESPACE HUMAN_SEQ_ACCESSION DESCRIPTION_BRIEF Genes down-regulated in response to UVB radiation in HFK cells (keratinocytes) immortalized by overexpression of HPV E6 and E7 viral oncogenes. DESCRIPTION_FULL Solar ultraviolet B (UVB) acts as both an initiator and promoter in models of multistage skin carcinogenesis. We found that, whereas UVB induces apoptosis in human papillomavirus-16 E6/7-immortalized keratinocytes, it inhibits markers of differentiation in human foreskin keratinocytes (HFK). Potential mechanisms for this differential response were examined by DNA microarray, which revealed that UVB alters the expression of three of the four human inhibitor of differentiation/DNA binding (Id) proteins that comprise a class of helix-loop-helix family of transcription factors involved in proliferation, differentiation, apoptosis, and carcinogenesis. These results were verified by RT-PCR and immunoblot analysis of control and UVB-irradiated primary and immortalized keratinocytes. Whereas Id1 was downregulated in both cell types, Id2 expression was upregulated in primary HFK, but not immortalized cells. In contrast, Id3 expression was significantly increased only in immortalized cells. The differential expression pattern of Id2 in response to UVB was recapitulated in reporter constructs containing the 5' regulatory regions of this gene. Id2 promoter activity increased in response to UVB in HFK, but not in immortalized cells. To identify the regulatory elements in the Id2 promoter that mediate transcriptional activation by UVB in HFK, promoter deletion/mutation analysis was performed. Deletion analysis revealed that transactivation involves a 166 bp region immediately upstream to the Id2 transcriptional start site and is independent of c-Myc. The consensus E twenty-six (ETS) binding site at -120 appears to mediate UVB transcriptional activation of Id2 because point mutations at this site completely abrogated this response. Chromatin immunoprecipitation and electrophoretic mobility-shift assays verified that the Id2 promoter interacts with known Id2 promoter (ETS) binding factors Erg1/2 and Fli1, but not with c-Myc; and this interaction is enhanced after UVB exposure. Similar to the effects of UVB exposure, ectopic expression of Id2 protein in primary HFK resulted in inhibition of differentiation, as shown by decreased levels of the terminal differentiation marker keratin K1 and inhibition of involucrin crosslinking. Reduction of Id2 expression by small interfering RNAs attenuated the UVB-induced inhibition of differentiation in these cells. These results suggest that UVB-induced inhibition of differentiation of primary HFK is at least, in part, due to the upregulation of Id2, and that upregulation of Id2 by UVB might predispose keratinocytes to carcinogenesis by preventing their normal differentiation program. PMID 16007217 GEOID AUTHORS Simbulan-Rosenthal CM,Trabosh V,Velarde A,Chou FP,Daher A,Tenzin F,Tokino T,Rosenthal DS CONTRIBUTOR Leona Saunders CONTRIBUTOR_ORG MSigDB Team EXACT_SOURCE Table 1: E6/E7-immortalized HFK: Fold delta < 0 FILTERED_BY_SIMILARITY EXTERNAL_NAMES_FOR_SIMILAR_TERMS EXTERNAL_DETAILS_URL SOURCE_MEMBERS AB000220,AF049910,AF051160,AF058696,D30783,J02973,L02320,L21990,L34155,M10905,M13929,M33336,M64174,M73554,M80899,M83216,M86667,S66213,U41387,U43195,U43916,U53204,X00588,X04434,X14787,X17033,X59618,X63629,X68060,X77956,X93921 GENE_SYMBOLS SEMA3C,TACC1,PTP4A1,NBN,EREG,THBD,RDX,SF3A2,LAMA3,FN1,MYC,PRKAR1A,JAK1,CCND1,AHNAK,CALD1,NAP1L1,ITGA6,DDX21,ROCK1,EMP1,PLEC,EGFR,IGF1R,THBS1,ITGA2,RRM2,CDH3,TOP2B,ID1,DUSP7 FOUNDER_NAMES