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Title: Self-interaction of NPM1 modulates multiple mechanisms of liquid–liquid phase separation

Nucleophosmin (NPM1) is an abundant, oligomeric protein in the granular component of the nucleolus with roles in ribosome biogenesis. Pentameric NPM1 undergoes liquid–liquid phase separation (LLPS) via heterotypic interactions with nucleolar components, including ribosomal RNA (rRNA) and proteins which display multivalent arginine-rich linear motifs (R-motifs), and is integral to the liquid-like nucleolar matrix. Here we show that NPM1 can also undergo LLPS via homotypic interactions between its polyampholytic intrinsically disordered regions, a mechanism that opposes LLPS via heterotypic interactions. Using a combination of biophysical techniques, including confocal microscopy, SAXS, analytical ultracentrifugation, and single-molecule fluorescence, we describe how conformational changes within NPM1 control valency and switching between the different LLPS mechanisms. We propose that this newly discovered interplay between multiple LLPS mechanisms may influence the direction of vectorial pre-ribosomal particle assembly within, and exit from the nucleolus as part of the ribosome biogenesis process.
Authors:
 [1] ;  [2] ; ORCiD logo [3] ;  [4] ;  [5] ; ORCiD logo [5] ;  [1] ;  [1] ;  [5] ; ORCiD logo [6]
  1. St. Jude Children’s Research Hospital, Memphis, TN (United States). Dept. of Structural Biology
  2. St. Jude Children’s Research Hospital, Memphis, TN (United States). Dept. of Structural Biology; Univ. of Tennessee Health Sciences Center, Memphis, TN (United States). Integrative Biomedical Sciences Program
  3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Biology and Biomedical Sciences Group. Biology and Soft Matter Division
  4. St. Jude Children’s Research Hospital, Memphis, TN (United States). Dept. of Structural Biology. Molecular Interaction Analysis Shared Resource
  5. Scripps Research Inst., La Jolla, CA (United States). Dept. of Integrative Structural and Computational Biology
  6. St. Jude Children’s Research Hospital, Memphis, TN (United States). Dept. of Structural Biology; Univ. of Tennessee Health Sciences Center, Memphis, TN (United States). Dept. of Microbiology, Immunology and Biochemistry
Publication Date:
Grant/Contract Number:
AC05-00OR22725; P30 CA021765; P30 CA21765; 5RO1GM115634; RO1 GM066833
Type:
Accepted Manuscript
Journal Name:
Nature Communications
Additional Journal Information:
Journal Volume: 9; Journal ID: ISSN 2041-1723
Publisher:
Nature Publishing Group
Research Org:
St. Jude Children’s Research Hospital, Memphis, TN (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Scripps Research Inst., La Jolla, CA (United States)
Sponsoring Org:
USDOE Office of Science (SC); National Inst. of Health (NIH) (United States); American Lebanese Syrian Associated Charities (ALSAC) (United States)
Country of Publication:
United States
Language:
English
Subject:
59 BASIC BIOLOGICAL SCIENCES; intrinsically disordered proteins; molecular conformation; SAXS; single-molecule biophysics; supramolecular assembly
OSTI Identifier:
1427597