Poster abstracts

Poster number 18 submitted by Mahesh Chemudupati

Nuclear export factors Gle1 and Nup42 are targeted to the nuclear envelope via two different mechanisms during interphase and mitosis

Mahesh Chemudupati (Department of Molecular Genetics, Ohio State University), Aysha H. Osmani (Department of Molecular Genetics, Ohio State University), Stephen A. Osmani (Department of Molecular Genetics, Ohio State University)

Abstract:
Nucleo-cytoplasmic transport is regulated by nuclear pore complexes (NPCs), which are proteinaceous conduits embedded in the nuclear envelope (NE). During mitosis in the model fungus Aspergillus nidulans, peripheral NPC proteins (Nups) disperse from the core NPC structure opening the nuclear pores thereby abolishing active transport and allowing diffusion in and out of mitotic nuclei. Paradoxically, two highly conserved peripheral Nups, Gle1 and Nup42 do not disperse from nuclei during mitosis. Intriguingly, both these proteins are involved in nuclear export, Gle1 being an mRNA export factor whereas Nup42 has roles in export of protein and mRNA. To ask how Gle1 remains at nuclei during mitosis, affinity purifications were performed and revealed that Gle1 co-purifies with a protein designated AN0162, which has a predicted C-terminal transmembrane (TM) domain. AN0162 locates in a manner identical to Gle1 at the NE during interphase and mitosis. We further find that deletion of AN0162, or removal of its TM domain, does not affect the NE localization of Gle1 during interphase but causes its dispersal from the NE specifically during mitosis. Gle1 and AN0162 also co-purify with Nup42. Deletion of AN0162 causes the mitotic-specific dispersal of Nup42 indicating that, like Gle1, Nup42 is located at nuclei via one mechanism during interphase and another, AN0162-dependent mechanism during mitosis. Why a mitotic-specific mechanism exists to retain these two nuclear export factors at nuclei during mitosis remains an open question. However, the nuclei of cells lacking AN0162 have a distinctive round shape, unlike the normal wild type oblong architecture, suggesting correct nuclear targeting of export factors to mitotic nuclei is required to maintain normal nuclear morphology during interphase.

Keywords: mitosis, cell-cycle, nuclear transport