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

人CRM1(HCRM1)是Exportin家族的成员之一，具有与富含亮氨酸的NES受体和支持HTLV-1Rex和蛋白多聚体的双重功能。为了研究Rex-CRM1相互作用和Rex多聚化的机制，我们重点研究了Rex功能受损的大鼠细胞。我们克隆了大鼠CRM1(RCRM1)的编码基因，并与hCRM1的Rex功能进行了比较。我们的结果表明，rCRM1不能有效地支持Rex的功能，因为它诱导Rex多聚化的能力很弱，尽管它与Rex NES结合很强。通过对人和大鼠CRM1序列的详细比较，然后构建嵌合体和突变的CRM1蛋白，我们能够确定与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多聚化的能力与有效的NES结合是分开的，这意味着CRM1与REX之间的相互作用比通过REX的NES区域的简单结合更高。我们还发现CRM1支持HIV Rev蛋白的多聚体。REV蛋白的羧基末端稳定了NES区与CRM1的相互作用，从而导致了REV蛋白的高效多聚化。

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.