Abstract
The nuclear–cytoplasmic protein transport is a critical process in cellular events. The identification of transport signals (nuclear localization signal and nuclear export signal) and their receptors has facilitated our understanding of this expanding field. Nuclear transport must be appropriately regulated to deliver proteins through the nuclear pore when their functions are required in the nucleus, and to export them into the cytoplasm when they are not needed in the nucleus. Altered nuclear transport processes have been observed in stressed cells, which would change gene expressions. Some viruses interfere with nuclear transport in host cells to evade immune defense. Moreover, certain transport factors negatively regulate nuclear protein transport in cells. Understanding the regulatory mechanisms of nuclear–cytoplasmic trafficking not only provides important information about cellular processes, but also is of use for developing specific inhibitors for transport pathways.
Highlights
In eukaryotic cells, the nuclear envelope separates the nucleus and the cytoplasm spatially and functionally
We focus on the mechanisms and roles of negative regulation of nuclear protein transport, the negative regulation exerted by transport factors themselves
Importin a/b1- and CRM1-dependent pathways, and other transport factor-mediated nuclear transport pathways would be impaired by stress treatment, indicating that cellular stress acts as a negative regulator of nuclear–cytoplasmic transport
Summary
The nuclear envelope separates the nucleus and the cytoplasm spatially and functionally. Transport factors recognize and transport cargo proteins containing these signals through the nuclear pore. Recent studies showed that other regulatory mechanisms control nuclear– cytoplasmic transport through transport factors and components of nuclear pore complexes (NPCs). Cellular stresses such as UV irradiation and heat shock have been shown to alter nuclear–cytoplasmic. NLS and NES have been identified in the primary sequences of proteins that are transported through the NPC (Jans et al 2000; Kutay & Guttinger 2005) These signals are recognized by transport factors, called importins and exportins, to be transported into or out of the nucleus (Major et al 2011).
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