Fantappié Marcelo R, Osman Ahmed, Ericsson Christer, Niles Edward G, LoVerde Philip T
Department of Microbiology and Immunology, Witebsky Center for Microbial Pathogenesis and Immunology, School of Medicine and Biomedical Sciences, 138 Farber Hall, State University of New York, Buffalo, NY 14214, USA.
Mol Biochem Parasitol. 2003 Sep;131(1):45-54. doi: 10.1016/s0166-6851(03)00188-9.
Drosophila (SINA) and human Seven in Absentia (SIAH-1 and SIAH-2) have been implicated in ubiquitin-mediated proteolysis of different target proteins. Using the Schistosoma mansoni nuclear receptor SmRXR2 as bait in a yeast two-hybrid system, we identified a DNA fragment that encodes part of the schistosome homologue of the Seven in Absentia protein (SmSINA). Screening of S. mansoni cDNA expression library resulted in the isolation of a cDNA containing the full-length coding region of SmSINA. SmSINA contains the characteristic structural features of other SINA proteins including a conserved N-terminal RING finger domain and a cysteine-rich C-terminus. We demonstrate that SmSINA associates with SmRXR2 and SmRXR1 both in vivo and in vitro, and define the binding domains in SmRXR2 and SmRXR1 that mediate their interaction. Schistosome SINA co-localizes with SmRXR2 and SmRXR1 in vitelline cells. In addition, we show that SmSINA stimulates the ubiquination of both SmRXR2 and SmRXR1 in vitro. Our findings suggest that SmSINA regulates ubiquitination and ubiquitin-induced degradation of schistosome nuclear receptors (RXR1 and RXR2) via the ubiquitin-proteasome pathway.
果蝇（SINA）和人类的“缺失七蛋白”（SIAH - 1和SIAH - 2）与不同靶蛋白的泛素介导的蛋白水解有关。在酵母双杂交系统中，以曼氏血吸虫核受体SmRXR2作为诱饵，我们鉴定出一个编码“缺失七蛋白”血吸虫同源物（SmSINA）部分序列的DNA片段。对曼氏血吸虫cDNA表达文库进行筛选，分离得到一个包含SmSINA全长编码区的cDNA。SmSINA具有其他SINA蛋白的特征性结构特点，包括保守的N端环指结构域和富含半胱氨酸的C端。我们证明SmSINA在体内和体外均能与SmRXR2和SmRXR1结合，并确定了SmRXR2和SmRXR1中介导它们相互作用的结合结构域。血吸虫SINA在卵黄细胞中与SmRXR2和SmRXR1共定位。此外，我们还表明SmSINA在体外能刺激SmRXR2和SmRXR1的泛素化。我们的研究结果表明，SmSINA通过泛素 - 蛋白酶体途径调节血吸虫核受体（RXR1和RXR2）的泛素化及泛素诱导的降解。
