Core promoter regulates the expression of cathepsin B gene in the fat body of Bombyx mori

• A 142 bp region in the BmCatB promoter was main tissue-specificity related region.
• EcREs are up-regulated in the regulatory of the BmCatB promoter.

Bombyx mori cathepsin B (BmCatB) is involved in the programmed cell death of the fat body during B. mori metamorphosis. For a better understanding of the functional regulatory mechanism, the promoter region of BmCatB in the transcriptional regulation has been identified and analyzed in the present study. BmCatB promoter region performed by the 5′ truncation or mutagenesis of EcREs was inserted in the pFA3Luc-A3RL double fluorescence expression vector to activate the fireflies luciferase (FLuc) gene. The results indicated that the dual-luciferase activity of BmCatB gene in the silkworm larval fat body is regulated by the length of promoter. Site-directed mutagenesis of EcRE experiment has shown that the EcREs are up-regulated significantly in the regulation of the BmCatB promoter. A 142 bp region (− 1165 to − 1023) and EcREs are the mainly fat-body tissue-specificity related region and could function as a core promoter element.

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