The nucleus is bound by an envelope consisting of the inner and outer nuclear membranes (INM and ONM), which is physically tethered to the cytoskeleton. In mammalian cells, INM-localized ion channels establish gradients between the nucleoplasm and perinuclear space, which in turn plays a role in signaling cascades. Nuclear import and export of proteins and other “cargo” is mediated passively by diffusion, or actively by a variety of cargo-selective transporters (KAPs, EXPs), which are largely conserved in yeast (Xpo), plants and animals, through envelope-spanning nuclear pore complexes (NPC), composed of dozens of proteins. Nuclear-shuttle proteins (hatched cargo) engage in multiple rounds of import and export. Protein and nucleic acid-protein complexes within the nucleus play roles in a plethora of physiologically relevant processes including, but not limited to, gene silencing (RISC complex), proteolysis (Proteasome), protein synthesis (Ribosome assembly), nucleolar functions (nucleolus), RNA processing (nuclear bodies) and chromatin organization, regulation, and transcription. In plants, many of the components of the nucleome are undefined and uncharacterized. Moreover, fundamental aspects of nuclear architecture in plants, like the presence of a nuclear lamina, remain equivocal.
Nucleome: The full complement of proteins that are trafficked to, into, and occasionally out of, the nucleus, in addition to those proteins that mediate nucleocytoplasmic transport per se
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