Differential expression and regulation by 20-hydroxyecdysone of mosquito ultraspiracle isoforms.
Differential expression and regulation by 20-hydroxyecdysone of mosquito ultraspiracle isoforms.
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DOI：
10.1006/dbio.1999.9575
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发表时间：
2000-02
影响因子：
2.7
通讯作者：
Sheng-fu Wang;Chao Li;Jinsong Zhu;K. Miura;R. Miksicek;A. Raikhel
中科院分区：
文献类型：
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作者：
Sheng-fu Wang;Chao Li;Jinsong Zhu;K. Miura;R. Miksicek;A. Raikhel
Ultraspiracle (USP) 是脊椎动物视黄醇 X 受体的昆虫同源物，是蜕皮类固醇受体 (EcR) 的必需二聚化伴侣。埃及伊蚊中有两种 USP 亚型：USP-A 和 USP-B，具有不同的 N 末端。在脂肪体和卵巢中，USP-A mRNA 在卵黄发生前期和晚期高度表达，对应于低蜕皮类固醇滴度的时期，而 USP-B mRNA 在卵黄发生期表现出最高水平，与高蜕皮类固醇滴度相关。值得注意的是，20-羟基蜕皮酮 (20E) 在体外脂肪体培养中对 USP 亚型转录物具有相反的作用。这种类固醇激素上调 USP-B 转录，它的存在是维持 USP-B 高水平表达所必需的。相反，20E 抑制 USP-A 转录的激活。尽管 EcR.USP-A 识别相同的蜕皮类固醇响应元件，但 EcR.USP-B 与它们结合的亲和力比 EcR.USP-A 高两倍。同样，EcR.USP-B 对 CV-1 细胞中报告基因的反式激活作用比 EcR.USP-A 强两倍。这些结果表明，在蚊子对 20E 的卵黄发生反应期间，USP-B 充当 EcR 的主要异二聚化伴侣。
Ultraspiracle (USP), the insect homologue of the vertebrate retinoid X receptor, is an obligatory dimerization partner for the ecdysteroid receptor (EcR). Two USP isoforms, USP-A and USP-B, with distinct N-termini, occur in the mosquito Aedes aegypti. In the fat body and ovary, USP-A mRNA is highly expressed during the pre- and late vitellogenic stages, corresponding to a period of low ecdysteroid titer, while USP-B mRNA exhibits its highest levels during the vitellogenic period, correlating with a high ecdysteroid titer. Remarkably, 20-hydroxyecdysone (20E) has opposite effects on USP isoform transcripts in in vitro fat body culture. This steroid hormone upregulates USP-B transcription and its presence is required to sustain a high level of USP-B expression. In contrast, 20E inhibits activation of USP-A transcription. Although EcR.USP-A recognizes the same ecdysteroid-responsive elements, EcR.USP-B binds them with an affinity twofold higher than that of EcR.USP-A. Likewise, EcR.USP-B transactivates a reporter gene in CV-1 cells twofold more strongly than EcR.USP-A. These results suggest that USP-B functions as a major heterodimerization partner for EcR during the vitellogenic response to 20E in the mosquito.