| Description |
Trafficking events across the nuclear envelope (NE) require specific interactions between cargo-receptor complexes and proteins of the nuclear pore complex (NPC). Although great strides have been made to elucidate protein and RNA transport pathways, many aspects of nuclear transport, particularly how cargo interacts with components of the NPC, remain undefined. In order to better understand the interactions that drive RNA export, I have focused on further defining the association between RNA cargo and the nucleoporin Nup153, a central regulator of nuclear transport. Overexpression of a C-terminal fragment of Nup153 in somatic cells inhibited poly(A)+ RNA export suggesting that Nup153 contributes to mRNA export. Further, perturbation of Nup153 function in Xenopus oocytes demonstrated Nup153 is important for mRNA, U snRNA and 5S rRNA export. Moreover, an RNA binding domain was mapped within the N-terminus of Nup 153 and was shown to bind RNA directly. The property of RNA association is conserved in Drosophila, Xenopus and human, underscoring the importance of this domain in higher eukaryotes. Although it is clear that Nup153 function is important for RNA export, exactly how this nuclear pore protein contributes to RNA export is unknown. One way to elucidate how Nup153 interfaces with RNA in the cell is to dissect the interactions mediated by this nucleoporin. Towards this end, the goal of this dissertation is to define the molecular targets of Nup153 in order to better understand the mechanisms by which Nup153, and the pore itself, functions. Initially, I found that the RNA binding domain (RBD) of Nup153 associates with cellular RNA and further characterization of this domain revealed that Nup153 preferentially associates with single-stranded RNA in a manner that distinctly mirrors properties that relay the identity of mRNA to the nuclear export machinery. I have also defined minimal length and base composition requirements for RNA association with Nup153. In collaboration with others, I have correlated Nup153-RNA association with functional RNA export in vivo. These collaborative studies indicate that direct contact between mRNA and Nup153 may occur cooperatively with protein contacts and that this interface between Nup153, mRNA and protein is critical to mRNA export and potentially concurrent mRNP remodeling and quality control. |
