A novel lipopolysaccharide response element in the Bombyx mori cecropin B promoter

Cecropin B is one of the major antibacterial peptides in the silkworm, Bomb yx mori. Transcription of the cecropin B gene (CecB) occurs rapidly after b acterial invasion. Using 235 base pairs (bp) of the CecB promoter region, a kappa B-related protein and two additional DNA-binding complexes (designat ed F2BPI and F4BP) were identified in nuclear extracts from immunized larva l fat body by the electrophoretic mobility shift assay (EMSA) (1). Further EMSA analyses indicated that the F2BPI-binding site was CATTA, and that F2B PI translocated from the cytoplasm to the nucleus after infection. In a rec ently established B. mori cell line, NISES-BoMo-DZ, 235 bp of CecB promoter linked to a reporter luciferase was activated 6-fold by stimulation with l ipopolysaccharide (LPS), which is a major trigger of CecB expression in lar vae. Truncation of the F2BPI-binding site from the promoter reduced the act ivation 2-fold. Deletion of either of two kappa B motifs also reduced promo ter activation 2-fold. Elimination of both the F2BPI-binding site and the k appa B motifs resulted in the complete loss of LPS inducibility. These resu lts indicate that the F2BPI-binding site is an LPS-responsive cis-element t hat is necessary for full activation of CecB.