Figure 2

Schematic representation of the RanGTP-dependent RNA export pathways in yeast (see [4]for a full description). Nuclear export of miRNA, rRNA, snRNA, and tRNA has been shown to follow the RanGTP-dependent exportin model. The nuclear export receptors, exportins, bind nuclear cargo together with RanGTP in the nucleus to form a ternary complex (RNA-exportin-RanGTP) that is translocated to the cytoplasm. The complex dissociates in the cytoplasm upon hydrolysis of RanGTP to release the cargo molecule. Different exportins are preferentially involved with the different RNA export pathways. Exportin t (XPOt) is involved with tRNA export, Exportin 5 (XPO5) in miRNA export whereas Exportin 1 (XPO1) is in charge of snRNA and rRNA export, as shown in the corresponding box. In the case of snRNA and rRNA export, additional adaptors are needed. After GTP hydrolysis in the cytoplasm, the import receptor, NTF2, carries RanGDP into the nucleus, where nucleotide exchange occurs by RCC1 to generate RanGTP.