Xu Yishi, Victorio Carla Bianca Luena, Ng Qimei, Prabakaran Mookkan, Tan Yee-Joo, Chua Kaw Bing
Temasek Life Sciences Laboratory, 1 Research Link, National University of Singapore, Singapore 117604, Singapore.
Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University Health System, National University of Singapore, Singapore 119228, Singapore.
Emerg Microbes Infect. 2016 Oct 12;5(10):e109. doi: 10.1038/emi.2016.110.
The Saffold virus (SAFV) genome is translated as a single long polyprotein precursor and co-translationally cleaved to yield 12 separate viral proteins. Little is known about the activities of SAFV proteins although their homologs in other picornaviruses have already been described. To further support research on functions and activities of respective viral proteins, we investigated the spatio-temporal distribution of SAFV proteins in Vero and HEp-2 cells that had been either transfected with plasmids that express individual viral proteins or infected with live SAFV. Our results revealed that, with the exception of the Leader (L) protein, all viral proteins were localized in the cytoplasm at all the time points assayed. The L protein was found in the cytoplasm at an early time point but was subsequently translocated to the nucleus of HEp-2, but not Vero, cells. This was observed in both transfected and infected cells. Further mutational analysis of L protein revealed that Threonine 58 of the Ser/Thr-rich domain of L protein is crucial for protein trafficking between the cytoplasm and nucleus in HEp-2 cells. These findings contribute to a deeper understanding and stimulate investigation of the differetial cellular responses of HEp-2 cells in comparison to other mammalian cell lines during SAFV infection.
萨福尔德病毒（SAFV）基因组作为一个单一的长多蛋白前体进行翻译，并在共翻译过程中被切割，产生12种不同的病毒蛋白。尽管SAFV蛋白在其他小RNA病毒中的同源物已经有过描述，但对SAFV蛋白的活性了解甚少。为了进一步支持对各个病毒蛋白的功能和活性的研究，我们研究了在转染了表达单个病毒蛋白的质粒或感染了活SAFV的Vero细胞和HEp-2细胞中SAFV蛋白的时空分布。我们的结果显示，除了前导（L）蛋白外，所有病毒蛋白在所有检测的时间点都定位于细胞质中。L蛋白在早期时间点位于细胞质中，但随后转移到HEp-2细胞而非Vero细胞的细胞核中。在转染细胞和感染细胞中均观察到这一现象。对L蛋白的进一步突变分析表明，L蛋白富含丝氨酸/苏氨酸结构域的苏氨酸58对于HEp-2细胞中蛋白在细胞质和细胞核之间的转运至关重要。这些发现有助于更深入地理解，并激发对SAFV感染期间HEp-2细胞与其他哺乳动物细胞系不同细胞反应的研究。
