Electronic Thesis and Dissertation Repository

Degree

Doctor of Philosophy

Program

Biology

Supervisor

Dr. Yuhai Cui

Abstract

Nuclear pore complexes (NPCs) are vital to nuclear-cytoplasmic communication in eukaryotes. The yeast Thp1-Sac3-Cdc31-Sus1 complex, also known as the TREX-2 complex, is anchored to the NPC via the nucleoporin Nup1, and is essential for mRNA export. In this study, the Arabidopsis homolog of the yeast TREX-2 complex was discovered. Physical and functional evidence support the identification of the Arabidopsis orthologs of the yeast Thp1 and Nup1. Of three Sac3 Arabidopsis homologs, two are putative TREX-2 components. Surprisingly, none are required for mRNA export as is the yeast Sac3. Physical association with TREX-2 was observed for the two Cdc31 homologs, but not the Sus1 homolog. Interactions of the Arabidopsis homolog of DSS1, a proteasome component in yeast and animals, with both the TREX-2 and the proteasome were observed, suggesting a possible link between the two complexes. Association of UCH1 and UCH2, the Arabidopsis homologs of de-ubiquitinating protease UCH37, with the proteasome was also demonstrated. Mutation in the core components of TREX-2 resulted in an altered response to plant hormones, suggesting a possible link between the mRNA export and hormone response. The Arabidopsis ortholog of Nup1 was found to be involved in pollen development and pollen tube guidance. This study identified the plant TREX-2 and added new components to both TREX-2 and the proteasome, thus providing a foundation and new perspectives for future studies of cellular processes involving nuclear export and protein degradation.

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