Cellular cofactors involved in transport of mRNAs of complex retroviruses and hepatitis B virus

人类CRM1 （hCRM1）是输出蛋白家族的一员，具有双重功能，作为富含亮氨酸的NES的受体和支持HTLV-1 Rex和蛋白的多聚。为了研究Rex- crm1相互作用和Rex多化的机制，我们重点研究了大鼠细胞中受损的Rex功能。我们克隆了一个编码大鼠CRM1的cDNA (rCRM1)，并与hCRM1在Rex功能上进行了比较。我们的研究结果表明，rCRM1不能有效地支持Rex功能，因为它诱导Rex多聚化的能力较差，尽管它与Rex NES结合强烈。通过对人类和大鼠CRM1序列的详细比较，以及嵌合体和突变CRM1蛋白的构建，我们确定了与Rex NES结合和Rex多聚化至关重要的氨基酸。这些结果表明，CRM1支持Rex多化的能力与有效的NES结合是可分离的，这意味着CRM1与Rex之间的相互作用比通过Rex的NES区域的简单关联更高阶。我们还发现CRM1支持HIV Rev蛋白的多聚。Rev蛋白的羧基末端稳定了NES区域与CRM1的相互作用，从而导致Rev蛋白的高效多聚。

Human CRM1 (hCRM1), a member of exportin family, has dual functions as a receptor for leucine-rich NES and in supporting the multimerization of HTLV-1 Rex and protein. To investigate the mechanism of Rex-CRM1 interaction and multimerization of Rex, we focused on impaired Rex function in rat cells. We cloned a cDNA encoding rat CRM1 (rCRM1) and compared with hCRM1 in Rex function. Our results indicate that rCRM1 does not support Rex function efficiently because of a poor ability to induce Rex multimerization, although it binds strongly to the Rex NES.Detailed comparison of human and rat CRM1 sequences, followed by construction of chimera and mutant CRM1 proteins allowed us to identify the amino acids critical for binding to the Rex NES and for Rex multimerization. These results suggested that the capacity of CRM1 to support Rex multimerization is separable from efficient NES binding, implying a higher order interaction between CRM1 and Rex than simple association via the NES region of Rex.We also found CRM1 supports multimerization of HIV Rev protein. Carboxy terminal of Rev protein stabilizes the interaction of NES region with CRM1, consequently leading to efficient multimerization of Rev proteins.