Determining Factors Influencing Nuclear Envelope and Nuclear Pore Complex Structure.

Abstract

The cell’s nuclear envelope (NE) has pores that are stabilized by nuclear pore complexes (NPC), large proteinaceous structures whose function is to mediate transport between the nucleus and cytoplasm. Although the transport process is well studied, the mechanism of NPC assembly from its protein constituents (nucleoporins) is less understood. To investigate NPC biogenesis, I investigated mutants that result in defective NPCs in Saccharomyces cerevisiae. First, I examined mutants in the GPI anchor pathway (gpi1) that resulted in mislocalized nucleoporins by testing two models: gpi1 mutants cause either misregulation of N-linked glycosylation or alter membrane properties. To test the models, I combined gpi1 mutants with a nucleoporin mutant that is susceptible to disruption of glycosylation or with mutants in membrane bending proteins. Select double mutant of each class rescued the growth phenotype of the single mutants. These results indicate that both of the models play a role in NPC assembly.

Secondly, we found the proteasome, a complex responsible for degrading proteins is involved in NPC assembly. In order to further investigate interactions between the NPC and the proteasome, I combined the proteasomal mutant with 3 classes of nuclear pore assembly (npa) mutants to test for synergistic interactions. Positive interactions were observed as the proteasome mutant rescued a temperature sensitive npa mutant providing further evidence for the role of the proteasome in NPC assembly