Abstract
Over the last two decades, multiple studies have explored the mechanisms governing mRNA export out of the nucleus, a crucial step in eukaryotic gene expression. During transcription and processing, mRNAs are assembled into messenger ribonucleoparticles (mRNPs). mRNPs are then exported through nuclear pore complexes (NPCs), which are large multiprotein assemblies made of several copies of a limited number of nucleoporins. A considerable effort has been put into the dissection of mRNA export through NPCs at both cellular and molecular levels, revealing the conserved contributions of a subset of nucleoporins in this process, from yeast to vertebrates. Several reports have also demonstrated the ability of NPCs to sort out properly-processed mRNPs for entry into the nuclear export pathway. Importantly, changes in mRNA export have been associated with post-translational modifications of nucleoporins or changes in NPC composition, depending on cell cycle progression, development or exposure to stress. How NPC modifications also impact on cellular mRNA export in disease situations, notably upon viral infection, is discussed.
Highlights
One of the defining hallmarks of eukaryotic cells is the compartmentalization of their genome, which enables the fine-tuning of gene expression processes, from mRNA synthesis and processing in the nucleus to translation in the cytoplasm
Exchanges of molecules between the two compartments exclusively rely on nuclear pore complexes (NPCs), which are multiprotein assemblies composed of multiple copies of ~30 different nucleoporins (Nups; Figure 1) and whose estimated mass is 60 MDa in yeast and 125 MDa in vertebrates
Multiple approaches have been used to characterize the main steps of mRNA export through NPCs and the nucleoporins involved in this process
Summary
One of the defining hallmarks of eukaryotic cells is the compartmentalization of their genome, which enables the fine-tuning of gene expression processes, from mRNA synthesis and processing in the nucleus to translation in the cytoplasm. The meshwork formed enables either the passive diffusion of small molecules or the selective transport of larger molecules (proteins and ribonucleoparticles) harboring nuclear localization or export signals (NLS/NES). These sequences are recognized by transport receptors (importins/exportins), which can dynamically interact with FG repeats [3]. Recent reviews have paid attention to the molecular mechanisms underlying mRNP assembly and export and to their tight connections with mRNA transcription, processing and nuclear organization, in yeast and/or in metazoans [4,5,6,7,8,9]. Nucleoporins (Nups) or NPC-associated proteins with a reported contribution to mRNA export are indicated in bold (see Table 1).
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