bims-nucpor Biomed News
on Nuclear pore complex and nucleoporins in stress, aging and disease
Issue of 2022–12–25
two papers selected by
Sara Mingu, Johannes Gutenberg University
  1. A nuclear pore complex-associated regulation of SUMOylation in meiosis.
  2. A minimal construct of nuclear-import receptor Karyopherin-β2 defines the regions critical for chaperone and disaggregation activity.
  1. Genes Cells. 2022 Dec 23.
    A nuclear pore complex-associated regulation of SUMOylation in meiosis.
    Hui-Ju Yang, Haruhiko Asakawa, Fu-An Li, Tokuko Haraguchi, Hsiu-Ming Shih, Yasushi Hiraoka.
      The nuclear pore complex (NPC) provides a permeable barrier between the nucleoplasm and cytoplasm. In a subset of NPC constituents that regulate meiosis in the fission yeast Schizosaccharomyces pombe, we found that nucleoporin Nup132 (homolog of human Nup133) deficiency resulted in transient leakage of nuclear proteins during meiosis I, as observed in the nup132 gene-deleted mutant. The nuclear protein leakage accompanied the liberation of the small ubiquitin-like modifier (SUMO)-specific ubiquitin-like protease 1 (Ulp1) from the NPC. Ulp1 retention at the nuclear pore prevented nuclear protein leakage and restored normal meiosis in a mutant lacking Nup132. Furthermore, using mass spectrometry analysis, we identified DNA topoisomerase 2 (Top2) and RCC1-related protein (Pim1) as the target proteins for SUMOylation. SUMOylation levels of Top2 and Pim1 were altered in meiotic cells lacking Nup132. HyperSUMOylated Top2 increased the binding affinity at the centromeres of nup132 gene-deleted meiotic cells. The Top2-12KR sumoylation mutant was less localized to the centromeric regions. Our results suggest that SUMOylation of chromatin-binding proteins is regulated by the NPC-bound SUMO-specific protease and is important for the progression of meiosis. This article is protected by copyright. All rights reserved.
    Keywords:  Meiosis; Nuclear pore complex; SENP2; Sumoylation; Topoisomerase; Ulp1
    DOI:  https://doi.org/10.1111/gtc.13003
  2. J Biol Chem. 2022 Dec 15. pii: S0021-9258(22)01249-2. [Epub ahead of print] 102806
    A minimal construct of nuclear-import receptor Karyopherin-β2 defines the regions critical for chaperone and disaggregation activity.
    Charlotte M Fare, Kevin Rhine, Andrew Lam, Sua Myong, James Shorter.
      Karyopherin-β2 (Kapβ2) is a nuclear-import receptor that recognizes proline-tyrosine nuclear localization signals (PY-NLSs) of diverse cytoplasmic cargo for transport to the nucleus. Kapβ2 cargo include several disease-linked RNA-binding proteins (RBPs) with prion-like domains (PrLDs), such as FUS, TAF15, EWSR1, hnRNPA1, and hnRNPA2. These RBPs with PrLDs are linked via pathology and genetics to debilitating degenerative disorders, including amyotrophic lateral sclerosis (ALS), frontotemporal dementia (FTD), and multisystem proteinopathy (MSP). Remarkably, Kapβ2 prevents and reverses aberrant phase transitions of these cargo, which is cytoprotective. However, the molecular determinants of Kapβ2 that enable these activities remain poorly understood, particularly from the standpoint of nuclear-import receptor architecture. Kapβ2 is a super-helical protein comprised of 20 HEAT repeats. Here, we design truncated variants of Kapβ2 and assess their ability to antagonize FUS aggregation and toxicity in yeast and FUS condensation at the pure protein level and in human cells. We find that HEAT repeats 8-20 of Kapβ2 recapitulate all salient features of Kapβ2 activity. By contrast, Kapβ2 truncations lacking even a single cargo-binding HEAT repeat display reduced activity. Thus, we define a minimal Kapβ2 construct for delivery in adeno-associated viruses as a potential therapeutic for ALS/FTD, MSP, and related disorders.
    Keywords:  FUS; chaperone; disaggregase; nuclear-import receptor; nucleocytoplasmic transport; phase separation
    DOI:  https://doi.org/10.1016/j.jbc.2022.102806
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