UVB IRRADIATION UP-REGULATION OF THE DROSOPHILA-1731 RETROTRANSPOSON LTR REQUIRES THE SAME SHORT SEQUENCE OF U3 REGION IN A HUMAN EPITHELIAL-CELL LINE AS IN DROSOPHILA CELLS

Phylogenetic analysis of the retrotransposon and retrovirus suggests a n evolutionary relationship between them and indicates that transactiv ation of the long terminal repeat (LTR)-containing retroelements could be ubiquitous. Using constructs expressing a reporter gene under the control of the entire or deleted LTR of 1731, which is a retrotranspos able element of Drosophila melanogaster, we were able to show that the UVB-irradiation activation of the 1731-LTR requires the same short se quence of U3 region in a human epithelial cell line as in Schneider's Drosophila cell line (S2). This sequence is similar to the binding seq uence of the members of the nuclear factor-kappa B (NF-kappa B)/rel fa mily. In addition, human colonic carcinoma cells (HT29), in response t o UVB-irradiation, produce some extracellular factor(s) that activates the 1731-LTR in nonirradiated cells.