ABSTRACT
CONTENTS 16.1 Introduction ............................................................................................................................. 261 16.2 Nuclear Pore Complex (NPC) and Its Regulation During Mitosis ........................................ 262
16.2.1 Identifi cation of the First NPC Proteins (Nups) from Filamentous Fungi Through Genetic Analysis of Mitotic Regulation ..................................................... 262
16.2.2 Mitotic Restructuring of the Aspergillus nidulans NPC .......................................... 264 16.2.3 Transmembrane Nups Remain at the Nuclear Envelope (NE) During Mitosis ........... 266 16.2.4 Structural Core of the NPC Remains at the NE During Mitosis ..................................... 266 16.2.5 FG Repeat Nups and Other Peripheral Nups Disperse from the Structural
Core of the NPC During Mitosis ............................................................................... 267 16.2.6 Gle1, a Predicted Peripheral Nup, Does Not Disperse from the Nuclear
Envelope During Mitosis ........................................................................................... 267 16.2.7 An-Nup2 Locates to DNA During Mitosis . .............................................................. 268 16.2.8 In Aspergillus nidulans, the RanGTP Gradient Could Shift from Across
the NE to Around DNA During Mitosis ................................................................... 268 16.2.9 Mitosis in Aspergillus nidulans Is an Evolutionary Intermediate Between
the Closed Mitosis of Yeasts and Open Mitosis of Higher Eukaryotes .................... 270 16.3 Soluble Nuclear Transporters of Aspergillus nidulans ........................................................... 271
16.3.1 Importin β-Like Super Family .................................................................................. 272 16.3.2 Nuclear Export Pathway and Its Regulation During
Transcriptional Control ............................................................................................. 273 16.3.3 Ntf2 and TAP/Nxt1 Transporters .............................................................................. 274
16.4 Conclusions and Future Directions for Research ................................................................... 274 Acknowledgments .............................................................................................................................. 274 References .......................................................................................................................................... 274
16.1 Introduction One of the defi ning features of eukaryotes is the sequestering of their genomes within nuclei. The nucleus is separated from the cytoplasm by the nuclear envelope (NE), which consists of lipid inner and outer membranes. The outer membrane is contiguous with the endoplasmic reticulum.1 In higher eukaryotes the nuclear lamina, consisting of intermediate fi lament like proteins, resides near the inner nuclear membrane and is thought to provide rigidity and the generally oval shape of the nucleus.2 Given that transcription is partitioned within nuclei, whereas protein translation occurs in the cytoplasm, it is essential to transport both RNA and protein in and out of nuclei. Such transport between the nucleoplasm and cytoplasm occurs through nuclear pore complexes (NPC), massive structures that provide regulated conduits through the NE. The NPC has a conserved overall structure and is constructed from multiple copies of ~30 NPC proteins termed nucleoporins, commonly abbreviated to Nups.3,4 The central transport channel of the NPC is formed by transmembrane Nups in combination with a conserved core multiNup
subcomplex. Other peripheral Nups reside in the central transport channel while some locate on either the nuclear or cytoplasm face of the NPC structure1 (Fig. 16.1a). Transport through the NPC is specifi c for cargoes containing nuclear localization sequences and nuclear export sequences. These targeting motifs bind specifi c soluble transporters, which then mediate interactions between the cargo and the NPC for active transport through the transport channel of the NPC. However, small inert molecules (<40 kD) can pass through the NPC by diffusion.
