Tanaka H, Sagisaka A, Suzuki N, Yamakawa M
Insect-Microbe Research Unit, National Institute of Agrobiological Sciences, Ibaraki, Japan.
Division of Insect Sciences, National Institute of Agrobiological Sciences, Ibaraki, Japan.
Insect Mol Biol. 2016 Oct;25(5):566-79. doi: 10.1111/imb.12244. Epub 2016 May 26.
E26 transformation-specific (Ets) family transcription factors are known to play roles in various biological phenomena, including immunity, in vertebrates. However, the mechanisms by which Ets proteins contribute to immunity in invertebrates remain poorly understood. In this study, we identified a cDNA encoding BmEts2, which is a putative orthologue of Drosophila Yan and human translocation-ets-leukemia/Ets-variant gene 6, from the silkworm Bombyx mori. Expression of the BmEts2 gene was significantly increased in the fat bodies of silkworm larvae in response to injection with Escherichia coli and Staphylococcus aureus. BmEts2 overexpression dramatically repressed B. mori Rels (BmRels)-mediated promoter activation of antimicrobial peptide genes in silkworm cells. Conversely, gene knockdown of BmEts2 significantly enhanced BmRels activity. In addition, two κB sites located on the 5' upstream region of cecropin B1 were found to be involved in the repression of BmRels-mediated promoter activation. Protein-competition analysis further demonstrated that BmEts2 competitively inhibited binding of BmRels to κB sites. Overall, BmEts2 acts as a repressor of BmRels-mediated transactivation of antimicrobial protein genes by inhibiting the binding of BmRels to κB sites.
已知E26转化特异性（Ets）家族转录因子在包括脊椎动物免疫在内的各种生物学现象中发挥作用。然而，Ets蛋白在无脊椎动物免疫中发挥作用的机制仍知之甚少。在本研究中，我们从家蚕中鉴定出一个编码BmEts2的cDNA，它是果蝇Yan和人类易位-ets-白血病/Ets-变异基因6的推定直系同源物。用大肠杆菌和金黄色葡萄球菌注射后，家蚕幼虫脂肪体中BmEts2基因的表达显著增加。BmEts2的过表达显著抑制了家蚕细胞中家蚕Rels（BmRels）介导的抗菌肽基因启动子激活。相反，BmEts2基因敲低显著增强了BmRels活性。此外，在家蚕抗菌肽B1的5'上游区域发现的两个κB位点参与了对BmRels介导的启动子激活的抑制。蛋白质竞争分析进一步表明，BmEts2竞争性抑制BmRels与κB位点的结合。总体而言，BmEts2通过抑制BmRels与κB位点的结合，作为BmRels介导的抗菌蛋白基因反式激活的阻遏物。
