State Key Laboratory of Silkworm Genome Biology, Biological Science Research Center, Southwest University, Beibei, Chongqing 400715, China.
College of Biotechnology, Southwest University, Beibei, Chongqing 400715, China.
Int J Biol Macromol. 2019 May 1;128:28-39. doi: 10.1016/j.ijbiomac.2019.01.092. Epub 2019 Jan 22.
Juvenile hormone (JH) and 20-hydroxyecdysone (20E) are the most important hormones in silkworm and play vital roles in silkworm development, metamorphosis, and silk protein synthesis. Fibroin modulator binding protein-1 (FMBP-1) is a novel transcription factor regulating fibroin heavy chain (fib-H) transcription in Bombyx mori. The roles of JH and 20E on FMBP-1 transcription are less known. Here, we show FMBP-1 transcription is repressed by juvenile hormone analog (JHA) and activated by 20E. We identify two Krüppel homolog 1 (Kr-h1) binding sites (KBS1 and KBS2) and an E74A binding site (EBS) in the promoter of FMBP-1. We demonstrate Kr-h1 directly binds to KBS1 and KBS2 to repress FMBP-1 transcription, and 20E promotes FMBP-1 transcription through E74A. In the presence of JH and 20E, E74A abolishes the repression of Kr-h1 and activates FMBP-1 transcription through direct binding to EBS between KBS1 and KBS2 in FMBP-1 promoter. Further, JHA and 20E treatment and RNA interference confirm the effects of JH and 20E on FMBP-1 transcription in vivo, thus affecting fib-H transcription. Our results reveal the molecular mechanism of FMBP-1 transcription regulated by the cross-talk between JH and 20E in Bombyx mori, and provide novel insights into FMBP-1 transcriptional regulation and silk protein synthesis.
保幼激素（JH）和 20-羟基蜕皮酮（20E）是家蚕最重要的激素，在家蚕发育、变态和丝蛋白合成中发挥重要作用。丝素调制结合蛋白-1（FMBP-1）是一种新型转录因子，调节家蚕丝素重链（fib-H）转录。JH 和 20E 对 FMBP-1 转录的作用知之甚少。在这里，我们发现 FMBP-1 转录受保幼激素类似物（JHA）抑制，被 20E 激活。我们在家蚕 FMBP-1 启动子中鉴定了两个 Krüppel 同源物 1（Kr-h1）结合位点（KBS1 和 KBS2）和一个 E74A 结合位点（EBS）。我们证明 Kr-h1 直接结合 KBS1 和 KBS2 抑制 FMBP-1 转录，20E 通过 E74A 促进 FMBP-1 转录。在 JH 和 20E 的存在下，E74A 消除了 Kr-h1 的抑制作用，并通过直接结合 FMBP-1 启动子中 KBS1 和 KBS2 之间的 EBS 激活 FMBP-1 转录。此外，JHA 和 20E 处理和 RNA 干扰实验证实了 JH 和 20E 对 FMBP-1 转录的体内影响，从而影响 fib-H 转录。我们的结果揭示了 JH 和 20E 在家蚕中相互作用调控 FMBP-1 转录的分子机制，为 FMBP-1 转录调控和丝蛋白合成提供了新的见解。
