A nuclear pore complex (NPC) is a large protein assembly that mediates the nucleocytoplasmic exchange of molecules. During the cell cycle, NPCs assemble, disassemble, and dynamically change their distribution on assembled nuclear envelope (NE), whereas in post-mitosis, NPCs are extremely stable. Extensive studies on its components, structure, and building blocks allow the study of its assembly and disassembly at the molecular level. Depending on the location that the initial components of this structure are built (e.g. chromatin versus double lipid bilayers of the nuclear envelope), the regulation and the mechanism of the assembly differ. Moreover, cell cycle dynamics of NPC are linked with INM proteins, lamins, lipid membranes, and the cell cycle signal, which show that NPC dynamics are highly regulated processes.

•SpHikeshi/Opi10 interacts with the S. pombe Hsp70 homolog Ssa2.•SpHikeshi/Opi10 imports Ssa2 in a HeLa-reconstituted nuclear transport system.•SpHikeshi/Opi10 is not required for cell survival in S. pombe after heat stress.•SpHikeshi/Opi10 depletion affects gene expression under optimal conditions.•SpHikeshi/Opi10 is required for cell growth in S. pombe during glucose deprivation.Human Hikeshi (HsHikeshi) is a nuclear import carrier for Hsp70s and is required for cell survival after heat shock. The Hikeshi homolog in Schizosaccharomyces pombe (SpHikeshi/Opi10) localizes to the nuclear rim, interacts with the Hsp70 homolog Ssa2, and mediates its nuclear import in a reconstituted mammalian nuclear transport system. However, SpHikeshi/Opi10 is not required for heat stress response and survival after heat stress. Instead, SpHikeshi/Opi10 is required for the normal expression of stress response genes under optimal conditions and for cell growth during glucose deprivation. Here, the functions of SpHikeshi/Opi10 are discussed and compared to the functions of HsHikeshi.

Pom121 is one of the integral membrane components of the nuclear pore complex (NPC) in vertebrate cells. Unlike rodent cells carrying a single POM121 gene, human cells possess multiple POM121 gene loci on chromosome 7q11.23, as a consequence of complex segmental-duplications in this region during human evolution. In HeLa cells, two “full-length” Pom121 are transcribed and translated by two distinct genetic loci. RNAi experiments showed that efficient depletion of both Pom121 proteins significantly reduces assembled NPCs on nuclear envelope. Pom121-depletion also induced clustering of NPCs, indicating its role on maintenance of NPC structure/organization.