J Biol Chem, Vol. 275, Issue 18, 13179-13182, May 5, 2000

ACCELERATED PUBLICATION
A Novel Lipopolysaccharide Response Element in the Bombyx mori Cecropin B Promoter^*

Kiyoko Taniai^§ and Shuichiro Tomita^¶

From the  Laboratory of Biological Defense, Department of Insect Physiology and Behavior and the ^¶ Department of Insect Genetics and Breeding, National Institute of Sericultural and Entomological Science, Tsukuba 305-8634, Japan

Cecropin B is one of the major antibacterial peptides in the silkworm, Bombyx mori. Transcription of the cecropin B gene (CecB) occurs rapidly after bacterial invasion. Using 235 base pairs (bp) of the CecB promoter region, a B-related protein and two additional DNA-binding complexes (designated F2BPI and F4BP) were identified in nuclear extracts from immunized larval fat body by the electrophoretic mobility shift assay (EMSA) (1). Further EMSA analyses indicated that the F2BPI-binding site was CATTA, and that F2BPI translocated from the cytoplasm to the nucleus after infection. In a recently 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 lipopolysaccharide (LPS), which is a major trigger of CecB expression in larvae. Truncation of the F2BPI-binding site from the promoter reduced the activation 2-fold. Deletion of either of two B motifs also reduced promoter activation 2-fold. Elimination of both the F2BPI-binding site and the B motifs resulted in the complete loss of LPS inducibility. These results indicate that the F2BPI-binding site is an LPS-responsive cis-element that is necessary for full activation of CecB.