Tanaka Hiromitsu, Yamamoto Masafumi, Moriyama Yuko, Yamao Masafumi, Furukawa Seiichi, Sagisaka Aki, Nakazawa Hiroshi, Mori Hajime, Yamakawa Minoru
Innate Immunity Laboratory, National Institute of Agrobiological Sciences, Owashi 1-2, Tsukuba, Ibaraki 305-8634, Japan.
Biochim Biophys Acta. 2005 Jul 25;1730(1):10-21. doi: 10.1016/j.bbaexp.2005.05.007.
Two cDNAs encoding novel Rel proteins were cloned from the silkworm, Bombyx mori. These cDNA clones (BmRelA and BmRelB) showed identical nucleotide sequences except for the 5'-region. BmRelB cDNA derived probably from an alternatively spliced mRNA lacked 241 bp nucleotides at the 5'-region of the BmRelA cDNA, resulting in a loss of the first 52 amino acids. Expression of antibacterial peptide genes was strongly inhibited upon infection with Micrococcus luteus in transgenic silkworms in which BmRel gene expression was knocked down, suggesting that these two Rel proteins are involved in activation of antibacterial peptide genes. Co-transfection experiments indicated that BmRelB activated the Attacin gene strongly and other genes to a lesser extent, whereas BmRelA activated Lebocin 4 gene strongly and Attacin and Lebocin 3 genes very weakly. The Rel homology domain of BmRelA and BmRelB was shown to bind specifically to kappaB sites of antibacterial peptide genes. Proline-rich domains of the BmRels were necessary for activation of antibacterial peptide genes. These results illustrate that a minor structural change in Rel proteins can provoke a dramatic differential activation of antibacterial peptide genes, suggesting a novel regulatory mechanism for insect antibacterial peptide gene expression.
从家蚕（Bombyx mori）中克隆出了两个编码新型Rel蛋白的cDNA。除了5'-区域外，这些cDNA克隆（BmRelA和BmRelB）显示出相同的核苷酸序列。BmRelB cDNA可能源自选择性剪接的mRNA，在BmRelA cDNA的5'-区域缺少241个碱基对的核苷酸，导致前52个氨基酸缺失。在用黄色微球菌感染的转基因家蚕中，当BmRel基因表达被敲低时，抗菌肽基因的表达受到强烈抑制，这表明这两种Rel蛋白参与抗菌肽基因的激活。共转染实验表明，BmRelB强烈激活Attacin基因，对其他基因的激活程度较小，而BmRelA强烈激活Lebocin 4基因，对Attacin和Lebocin 3基因的激活非常弱。结果表明，BmRelA和BmRelB的Rel同源结构域能特异性结合抗菌肽基因的κB位点。BmRel的富含脯氨酸结构域对抗菌肽基因的激活是必需的。这些结果表明，Rel蛋白的微小结构变化可引发抗菌肽基因的显著差异激活，提示昆虫抗菌肽基因表达存在一种新的调控机制。
