Methods and assays to investigate nuclear export.

Abstract

A hallmark of eukaryotic cells is their spatial and functional separation into the nucleus and the cytoplasm by the nuclear envelope. Although this separation introduces a potent and sophisticated level of regulation not existing in prokaryotes, it also requires a highly effective and selective transport machinery. All known transport between the nucleus and the cytoplasm occurs through the nuclear pore complex (NPC) (for reviews, see Fabre and Hurt 1997; Gant et al. 1998; Pante and Aebi 1996). Theoretically, proteins with masses <40kDa can enter and leave the nucleus by passive diffusion. However, even most of the smaller proteins and nucleic acids appear to be transported by signal-mediated pathways, probably because signal-mediated trafficking is more efficient and more amenable to specific regulation than diffusion. The most prevalent nuclear export signals (NESs) found consist of a short leucine-rich stretch of amino acids in which the leucine residues are critical for function (for review, see GÖrlich and Kutay 1999; Mattaj and Englmeier 1998 and references therein). Leucine-rich NESs have been identified in an increasing number of cellular and viral proteins executing quite heterologous biological functions. As extensively reviewed in the individual chapters of this book, viruses efficiently exploit the cellular transport machinery in order to successfully parasitize the cell. This chapter will summarize existing in vitro and in vivo assay systems to study nuclear export in mammalian cells, focusing especially on novel experimental approaches. As a result of space limitation, important primary papers will not be quoted and we apologize to our colleagues for these omissions.KeywordsNuclear ExportNuclear ImportNuclear Pore ComplexNuclear Export SignalNucleocytoplasmic TransportThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.