Kapitskaya M, Wang S, Cress D E, Dhadialla T S, Raikhel A S
Department of Entomology, Michigan State University, East Lansing 48824, USA.
Mol Cell Endocrinol. 1996 Aug 9;121(2):119-32. doi: 10.1016/0303-7207(96)03847-6.
We report the cloning and characterization of two isoforms of the Ultraspiracle homologue (AaUSP) from the mosquito, Aedes aegypti. The 2.33-kb AaUSPa cDNA has an open reading frame (ORF) of 484 amino acids encoding a polypeptide of 54 kDa, whereas the 2.14-kb AaUSPb ORF of 459 amino acids encodes a 51.3 kDa polypeptide. The AaUSPa and AaUSPb proteins differ only in the N-terminal portion of the variable A/B domain. The AaUSP DNA-binding domain shares 92% and 97% identities with the respective domains of the Drosophila (DmUSP) and Bombyx (BmUSP) Ultraspiracles. However, the AaUSP ligand-binding domain is only 57% and 52% identical to those of DmUSP and BmUSP, respectively. In spite of the relatively low level of sequence conservation, electrophoretic mobility shift assay (EMSA) and hormone-binding assay clearly demonstrated that the products of the AaUSPa and AaUSPb cDNAs are functional heterodimeric partners of the mosquito ecdysteroid receptor. In vitellogenic tissues, each of the two AaUSP isoforms is expressed differently: the AaUSPa is predominant in the fat body and the AaUSPb in the ovary. The kinetics of ovarian AaUSP mRNA coincide with those of the ecdysteroid receptor, being elevated during the previtellogenic period and shortly after the onset of vitellogenesis. In contrast, the level of the AaUSP in the fat body remains relatively constant throughout most of the vitellogenic cycle.
我们报道了从埃及伊蚊中克隆和鉴定出的超气门同源物（AaUSP）的两种亚型。2.33 kb的AaUSPa cDNA具有一个484个氨基酸的开放阅读框（ORF），编码一个54 kDa的多肽，而2.14 kb的AaUSPb的459个氨基酸的ORF编码一个51.3 kDa的多肽。AaUSPa和AaUSPb蛋白仅在可变A/B结构域的N端部分有所不同。AaUSP的DNA结合结构域与果蝇（DmUSP）和家蚕（BmUSP）的超气门各自的结构域分别具有92%和97%的同一性。然而，AaUSP的配体结合结构域与DmUSP和BmUSP的配体结合结构域分别只有57%和52%的同一性。尽管序列保守性相对较低，但电泳迁移率变动分析（EMSA）和激素结合分析清楚地表明，AaUSPa和AaUSPb cDNA的产物是埃及伊蚊蜕皮甾体受体的功能性异二聚体伴侣。在卵黄发生组织中，两种AaUSP亚型的表达各不相同：AaUSPa在脂肪体中占主导，而AaUSPb在卵巢中占主导。卵巢AaUSP mRNA的动力学与蜕皮甾体受体的动力学一致，在前卵黄发生期和卵黄发生开始后不久升高。相比之下，在大多数卵黄发生周期中，脂肪体中AaUSP的水平保持相对恒定。
