Abstract
Nuclear export of messenger RNA (mRNA) through the nuclear pore complex (NPC) is an indispensable step to ensure protein translation in the cytoplasm of eukaryotic cells. mRNA is not translocated on its own, but it forms ribonuclear particles (mRNPs) in association with proteins that are crucial for its metabolism, some of which; like Mex67/MTR2-NXF1/NXT1; are key players for its translocation to the cytoplasm. In this review, I will summarize our current body of knowledge on the basic characteristics of mRNA export through the NPC. To be granted passage, the mRNP cargo needs to bind transport receptors, which facilitate the nuclear export. During NPC transport, mRNPs undergo compositional and conformational changes. The interactions between mRNP and the central channel of NPC are described; together with the multiple quality control steps that mRNPs undergo at the different rings of the NPC to ensure only proper export of mature transcripts to the cytoplasm. I conclude by mentioning new opportunities that arise from bottom up approaches for a mechanistic understanding of nuclear export.
Highlights
Nuclear export of messenger RNA through the nuclear pore complex (NPC) is an indispensable step to ensure protein translation in the cytoplasm of eukaryotic cells. messenger RNAs (mRNAs) is not translocated on its own, but it forms ribonuclear particles in association with proteins that are crucial for its metabolism, some of which; like Mex67/MTR2-NXF1/NXT1; are key players for its translocation to the cytoplasm
This strongly suggests that the presence of a population of NXF1 at the NPC is required for mRNA export independently of NXF1 loading on mRNA, which is further supported by an elegant rescue experiment where a Nup116-Mex67 fusion protein rescued deletion of Mex67 alone [113]
The crew of proteins involved in mRNA export have been mostly elucidated, as well as many of the molecular mechanisms involved
Summary
The passage of mRNAs to the cytoplasm occurs through the nuclear pore complexes (NPCs) that, with their ~125 MDa, make the cellular largest protein complex, spanning the double nuclear envelope. Elucidating in detail the molecular mechanisms underlying how mRNA production, export and regulation are linked to RBPs represents a very difficult task This is due to the large variety of RBPs, to their RNA sequence specificity or lack thereof, to the variety of mRNAs, and because of the extremely high number of possible combinatorial interactions between mRNAs and RBPs [6]. Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations This huge set lies in the 3D organization of the mRNPs. Recent years have provided key new insights into mRNP morphology, but mostly in the context of translation [7,8]. This review intends to highlight recent findings related to mRNP maturation into export-competent complexes, the key interactions with members of the nuclear pore complex (recapitulated in Table 1), and the perspective of novel approaches relating to questions on the mRNA export process. A multisubunit complex, anchored to the NPC basket
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