bims-nucpor 2021-06-20 papers

Issue of 2021–06–20
three papers selected by
Sara Mingu, Johannes Gutenberg University

Dev Cell. 2021 Jun 09. pii: S1534-5807(21)00444-5. [Epub ahead of print]

Inherited nuclear pore substructures template post-mitotic pore assembly.

Yi-Ying Chou, Srigokul Upadhyayula, Justin Houser, Kangmin He, Wesley Skillern, Gustavo Scanavachi, Song Dang, Anwesha Sanyal, Kazuka G Ohashi, Giuseppe Di Caprio, Alex J B Kreutzberger, Tegy John Vadakkan, Tom Kirchhausen.

Nuclear envelope assembly during late mitosis includes rapid formation of several thousand complete nuclear pore complexes (NPCs). This efficient use of NPC components (nucleoporins or "NUPs") is essential for ensuring immediate nucleocytoplasmic communication in each daughter cell. We show that octameric subassemblies of outer and inner nuclear pore rings remain intact in the mitotic endoplasmic reticulum (ER) after NPC disassembly during prophase. These "inherited" subassemblies then incorporate into NPCs during post-mitotic pore formation. We further show that the stable subassemblies persist through multiple rounds of cell division and the accompanying rounds of NPC mitotic disassembly and post-mitotic assembly. De novo formation of NPCs from newly synthesized NUPs during interphase will then have a distinct initiation mechanism. We postulate that a yet-to-be-identified modification marks and "immortalizes" one or more components of the specific octameric outer and inner ring subcomplexes that then template post-mitotic NPC assembly during subsequent cell cycles.

Keywords: FIB-SEM; cell division; endoplasmic reticulum; inheritance; lattice light-sheet microscopy; live cell imaging; mitosis; nuclear envelope; nuclear pore complex; spinning disk confocal microscopy

DOI: https://doi.org/10.1016/j.devcel.2021.05.015

Cold Spring Harb Perspect Biol. 2021 Jun 14. pii: a039438. [Epub ahead of print]

The Nuclear Pore Complex as a Transcription Regulator.

Michael Chas Sumner, Jason Brickner.

The nuclear pore complex (NPC) is a highly conserved channel in the nuclear envelope that mediates mRNA export to the cytosol and bidirectional protein transport. Many chromosomal loci physically interact with nuclear pore proteins (Nups), and interactions with Nups can promote transcriptional repression, transcriptional activation, and transcriptional poising. Interaction with the NPC also affects the spatial arrangement of genes, interchromosomal clustering, and folding of topologically associated domains. Thus, the NPC is a spatial organizer of the genome and regulator of genome function.

DOI: https://doi.org/10.1101/cshperspect.a039438

Cell Rep. 2021 Jun 15. pii: S2211-1247(21)00595-7. [Epub ahead of print]35(11): 109236

Correct dosage of X chromosome transcription is controlled by a nuclear pore component.

Jennifer R Aleman, Terra M Kuhn, Pau Pascual-Garcia, Janko Gospocic, Yemin Lan, Roberto Bonasio, Shawn C Little, Maya Capelson.

Dosage compensation in Drosophila melanogaster involves a 2-fold transcriptional upregulation of the male X chromosome, which relies on the X-chromosome-binding males-specific lethal (MSL) complex. However, how such 2-fold precision is accomplished remains unclear. Here, we show that a nuclear pore component, Mtor, is involved in setting the correct levels of transcription from the male X chromosome. Using larval tissues, we demonstrate that the depletion of Mtor results in selective upregulation at MSL targets of the male X, beyond the required 2-fold. Mtor and MSL components interact genetically, and depletion of Mtor can rescue the male lethality phenotype of MSL components. Using RNA fluorescence in situ hybridization (FISH) analysis and nascent transcript sequencing, we find that the effect of Mtor is not due to defects in mRNA export but occurs at the level of nascent transcription. These findings demonstrate a physiological role for Mtor in the process of dosage compensation, as a transcriptional attenuator of X chromosome gene expression.

Keywords: MSL; Megator; Mtor; X chromosome; dosage compensation; nuclear pore complex; nucleoporin; transcription

DOI: https://doi.org/10.1016/j.celrep.2021.109236