Regulation Mechanism of Gene Expression by Insect Juvenile Hormone and Identification of Juvenile Hormone Receptor

昆虫幼虫激素（JH）是昆虫调节变态、滞育、多态性、繁殖等的重要激素。JH的作用方式的分子机制已被研究，并被证明可以调节这些生理现象相关基因的表达。然而，JH受体尚未被鉴定和分离。用PCR方法从家蚕中分离出一种编码新型孤儿受体（GRF）的cDNA，该受体与家蚕bFTZ-F1和脊椎动物生殖细胞核因子最密切相关。在大多数组织中检测到主要的GRF mRNA为8 kb的转录本，其数量随循环外甾体浓度而延迟。GRF的表达模式与果蝇早期晚期基因DHR3的家蝇同源基因相似，在所有阶段和组织中均先于bFTZ-F1表达。因此，GRF蛋白可能在许多组织中都是必需的，但在时间上受到限制，这表明GRF在激素诱导的转录级联中具有明确的功能。GRF蛋白在体外通过50 -TCA延伸与单雌激素受体半位点AGGTCA结合，因此是孤儿受体bFTZ-F1和DHR39的潜在共同调节剂。

Insect juvenile hormone (JH) is an important hormone for insect to regulate metamorphosis, diapause, polymorphism, reproduction and so on. Molecular mechanism of mode of action of JH have been studied, and shown to regulate the expression of genes related to those physiological phenomena. However, JH receptor has not been identified and isolated.A PCR approach has been used to isolate, form Bombyx mori, a cDNA encoding a novel orphan receptor (GRF) that is most closely related to Bombyx bFTZ-F1 and to the vertebrate germ cell nuclear factor. The major GRF mRNA is detected in most tissues as an 8-kb transcript whose amount follows the circulating ecdysteroid concentration with a delay. The expression pattern of GRF is similar to that of the Bombyx homologue of the Drosophila early late gene DHR3, and precedes that of bFTZ-F1 in all stages and tissues examined. The GRF protein is thus likely to be required in many tissues, but in a temporally restricted manner suggesting that GRF has a well-defined function in the ecdysteroid-induced transcription cascade. The GRF protein binds in vitro to a single oestrogen receptor half-site AGGTCA preceded by a 50 -TCA extension, and is therefore a potential co-regulator of the orphan receptors bFTZ-F1 and DHR39.