bims-nucpor 2022-10-16 papers

Issue of 2022–10–16
three papers selected by
Sara Mingu, Johannes Gutenberg University

Mol Biol Cell. 2022 Oct 12. mbcE22010027

Insights into the role of Nup62 and Nup93 in assembling cytoplasmic ring and central transport channel of the nuclear pore complex.

Pankaj K Madheshiya, Ekta Shukla, Jyotsana Singh, Shrankhla Bawaria, Mohammed Yousuf Ansari, Radha Chauhan.

The nuclear pore complex (NPC) is a highly modular assembly of 34 distinct nucleoporins (Nups), to form a versatile transport channel between the nucleus and cytoplasm. Among them, Nup62 is known as an essential component for nuclear transport while, Nup93 for the proper nuclear envelope assembly. These Nups constitute various NPC subcomplexes: such as central transport channel (CTC), cytoplasmic ring (CR) and inner ring (IR). However, how they play their role in the NPC assembly and transport activity is not clear. Here we delineated the interacting regions, conducted biochemical reconstitution and structural characterization of the mammalian CR complex to reveal its intrinsic dynamic behaviour and a distinct '4' shaped architecture resembling the CTC complex. Our in vitro reconstitution data demonstrate that Nup62 coiled-coil domain is critical to form both Nup62322-525•Nup88517-742 and Nup62322-525•Nup88517-742•Nup214693-926 heterotrimers and both can bind to the Nup931-150. We therefore propose that the Nup93 act as a 'sensor' to bind to Nup62 shared heterotrimers including Nup62•Nup54 heterotrimer of the CTC, which was not shown previously as an interacting partner. Altogether, our biochemical study suggests that the Nup62 via its coiled-coil domain is central to form compositionally distinct yet structurally similar heterotrimers, and the Nup93 binds these diverse heterotrimers non-selectively.

DOI: https://doi.org/10.1091/mbc.E22-01-0027

Mol Cell. 2022 Oct 06. pii: S1097-2765(22)00908-X. [Epub ahead of print]

Nuclear mRNA metabolism drives selective basket assembly on a subset of nuclear pore complexes in budding yeast.

Pierre Bensidoun, Taylor Reiter, Ben Montpetit, Daniel Zenklusen, Marlene Oeffinger.

To determine which transcripts should reach the cytoplasm for translation, eukaryotic cells have established mechanisms to regulate selective mRNA export through the nuclear pore complex (NPC). The nuclear basket, a substructure of the NPC protruding into the nucleoplasm, is thought to function as a stable platform where mRNA-protein complexes (mRNPs) are rearranged and undergo quality control prior to export, ensuring that only mature mRNAs reach the cytoplasm. Here, we use proteomic, genetic, live-cell, and single-molecule resolution microscopy approaches in budding yeast to demonstrate that basket formation is dependent on RNA polymerase II transcription and subsequent mRNP processing. We further show that while all NPCs can bind Mlp1, baskets assemble only on a subset of nucleoplasmic NPCs, and these basket-containing NPCs associate a distinct protein and RNA interactome. Taken together, our data point toward NPC heterogeneity and an RNA-dependent mechanism for functionalization of NPCs in budding yeast through nuclear basket assembly.

Keywords: Mlp1; NPC heterogeneity; basket accessory interactome; mRNA export; mRNA processing; nuclear basket; nuclear compartmentalization; nuclear pore complex; nucleolus; poly(A) transcripts

DOI: https://doi.org/10.1016/j.molcel.2022.09.019

Cells. 2022 Sep 22. pii: 2957. [Epub ahead of print]11(19):

Bioinformatics and Functional Analysis of a New Nuclear Localization Sequence of the Influenza A Virus Nucleoprotein.

Nhan L T Nguyen, Nelly Panté.

Influenza viruses deliver their genome into the nucleus of infected cells for replication. This process is mediated by the viral nucleoprotein (NP), which contains two nuclear localization sequences (NLSs): NLS1 at the N-terminus and a recently identified NLS2 (212GRKTR216). Through mutagenesis and functional studies, we demonstrated that NP must have both NLSs for an efficient nuclear import. As with other NLSs, there may be variations in the basic residues of NLS2 in different strains of the virus, which may affect the nuclear import of the viral genome. Although all NLS2 variants fused to the GFP mediated nuclear import of GFP, bioinformatics showed that 98.8% of reported NP sequences contained either the wild-type sequence 212GRKTR216 or 212GRRTR216. Bioinformatics analyses used to study the presence of NLS2 variants in other viral and nuclear proteins resulted in very low hits, with only 0.4% of human nuclear proteins containing putative NLS2. From these, we studied the nucleolar protein 14 (NOP14) and found that NLS2 does not play a role in the nuclear import of this protein but in its nucleolar localization. We also discovered a functional NLS at the C-terminus of NOP14. Our findings indicate that NLS2 is a highly conserved influenza A NP sequence.

Keywords: NLS; NOP14; influenza A virus; nuclear import; nuclear localization sequence; nucleolar protein 14; nucleoprotein

DOI: https://doi.org/10.3390/cells11192957