{"id":{"repo_id":"tenn-hsc","oai_identifier":"oai:dc.uthsc.edu:dissertations-1411"},"canonical_url":"https://search.dev.ndltd.org/etd/tenn-hsc/oai:dc.uthsc.edu:dissertations-1411","repository":{"repo_id":"tenn-hsc","name":"University of Tennessee Health Science Center","base_url":"https://dc.uthsc.edu/do/oai/"},"display":{"title":"The Nucleolar Protein Nucleophosmin Undergoes Liquid-Liquid Phase Separation with Arginine-Rich Nucleolar Proteins through Weak, Multivalent Electrostatic Interactions","abstract":"Nucleoli are nuclear membrane-less organelles that are the sites for ribosome biogenesis and serve as sensors of cellular stress. Weak, multivalent protein-protein interactions and interactions between disordered, low complexity domains (LCDs) and rRNA have been shown to promote liquid-liquid phase separation (LLPS) in vitro, suggesting a basis for the liquid-like behavior of nucleoli. Nucleophosmin (NPM1), a multifunctional and highly abundant nucleolar protein, exhibits structural features associated with LLPS suggesting a role in nucleolar organization. Specifically, NPM1 forms a pentamer through its N-terminal oligomerization domain and can bind to rRNA through its C-terminal nucleic acid binding domain. Multiple acidic tracts throughout NPM1, two within an intrinsically disordered region (IDR), confer additional multivalency and mediate interactions with proteins that contain multiple arginine-rich motifs (R-proteins). Using a variety of techniques, we have identified several nucleolar R-proteins which bind to and phase separate with NPM1. Here we show that the liquid-like properties of NPM1 droplets can be tuned by modulating the extent of electrostatic interactions within the droplet. We propose that a hierarchy of R-motifs, varying in valency and affinity, within nucleolar R-proteins exists which leads to a heterogeneous network of interactions between proteins and rRNA within nucleoli, thus promoting formation of a dynamic liquid-like phase conducive to ribosome biogenesis and other nucleolar functions.","abstract_html":"Nucleoli are nuclear membrane-less organelles that are the sites for ribosome biogenesis and serve as sensors of cellular stress. Weak, multivalent protein-protein interactions and interactions between disordered, low complexity domains (LCDs) and rRNA have been shown to promote liquid-liquid phase separation (LLPS) in vitro, suggesting a basis for the liquid-like behavior of nucleoli. Nucleophosmin (NPM1), a multifunctional and highly abundant nucleolar protein, exhibits structural features associated with LLPS suggesting a role in nucleolar organization. Specifically, NPM1 forms a pentamer through its N-terminal oligomerization domain and can bind to rRNA through its C-terminal nucleic acid binding domain. Multiple acidic tracts throughout NPM1, two within an intrinsically disordered region (IDR), confer additional multivalency and mediate interactions with proteins that contain multiple arginine-rich motifs (R-proteins). Using a variety of techniques, we have identified several nucleolar R-proteins which bind to and phase separate with NPM1. Here we show that the liquid-like properties of NPM1 droplets can be tuned by modulating the extent of electrostatic interactions within the droplet. We propose that a hierarchy of R-motifs, varying in valency and affinity, within nucleolar R-proteins exists which leads to a heterogeneous network of interactions between proteins and rRNA within nucleoli, thus promoting formation of a dynamic liquid-like phase conducive to ribosome biogenesis and other nucleolar functions.","abstract_has_math":false,"creators":["Cika, Jaclyn Alicia"],"institution":null,"degree_name":"Master of Science (MS)","degree_level":"Thesis","degree_discipline":"Biomedical Sciences","degree_department":null,"school":null,"contributors":["Richard Kriwacki, Ph.D."],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2016,"date_issued":"2016-12-01T08:00:00Z","date_published":"2016-12-01T08:00:00Z","updated_at":"2026-07-24T05:00:33Z","subjects":["Membrane-less organelle","Nucleolus","Phase Separation","Structural Biology","Biological Phenomena, Cell Phenomena, and Immunity","Medical Cell Biology","Medical Sciences","Medicine and Health Sciences"],"languages":[],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"https://dc.uthsc.edu/dissertations/411","outbound_label":"Repository record","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Richard Kriwacki, Ph.D."]},{"key":"dc:creator","label":"Author","values":["Cika, Jaclyn Alicia"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.available","label":"Dc Date Available","values":["2017-01-25T08:00:00Z"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Biomedical Sciences"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Thesis"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Master of Science (MS)"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Membrane-less organelle","Nucleolus","Phase Separation","Structural Biology","Biological Phenomena, Cell Phenomena, and Immunity","Medical Cell Biology","Medical Sciences","Medicine and Health Sciences"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["https://dc.uthsc.edu/dissertations/411"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["Nucleoli are nuclear membrane-less organelles that are the sites for ribosome biogenesis and serve as sensors of cellular stress. Weak, multivalent protein-protein interactions and interactions between disordered, low complexity domains (LCDs) and rRNA have been shown to promote liquid-liquid phase separation (LLPS) in vitro, suggesting a basis for the liquid-like behavior of nucleoli. Nucleophosmin (NPM1), a multifunctional and highly abundant nucleolar protein, exhibits structural features associated with LLPS suggesting a role in nucleolar organization. Specifically, NPM1 forms a pentamer through its N-terminal oligomerization domain and can bind to rRNA through its C-terminal nucleic acid binding domain. Multiple acidic tracts throughout NPM1, two within an intrinsically disordered region (IDR), confer additional multivalency and mediate interactions with proteins that contain multiple arginine-rich motifs (R-proteins). Using a variety of techniques, we have identified several nucleolar R-proteins which bind to and phase separate with NPM1. Here we show that the liquid-like properties of NPM1 droplets can be tuned by modulating the extent of electrostatic interactions within the droplet. We propose that a hierarchy of R-motifs, varying in valency and affinity, within nucleolar R-proteins exists which leads to a heterogeneous network of interactions between proteins and rRNA within nucleoli, thus promoting formation of a dynamic liquid-like phase conducive to ribosome biogenesis and other nucleolar functions."]},{"key":"dc:title","label":"Title","values":["The Nucleolar Protein Nucleophosmin Undergoes Liquid-Liquid Phase Separation with Arginine-Rich Nucleolar Proteins through Weak, Multivalent Electrostatic Interactions"]}]}],"canonical_facts":{"dc:contributor":["Richard Kriwacki, Ph.D."],"dc:creator":["Cika, Jaclyn Alicia"],"dc:date.available":["2017-01-25T08:00:00Z"],"dc:description.abstract":["Nucleoli are nuclear membrane-less organelles that are the sites for ribosome biogenesis and serve as sensors of cellular stress. Weak, multivalent protein-protein interactions and interactions between disordered, low complexity domains (LCDs) and rRNA have been shown to promote liquid-liquid phase separation (LLPS) in vitro, suggesting a basis for the liquid-like behavior of nucleoli. Nucleophosmin (NPM1), a multifunctional and highly abundant nucleolar protein, exhibits structural features associated with LLPS suggesting a role in nucleolar organization. Specifically, NPM1 forms a pentamer through its N-terminal oligomerization domain and can bind to rRNA through its C-terminal nucleic acid binding domain. Multiple acidic tracts throughout NPM1, two within an intrinsically disordered region (IDR), confer additional multivalency and mediate interactions with proteins that contain multiple arginine-rich motifs (R-proteins). Using a variety of techniques, we have identified several nucleolar R-proteins which bind to and phase separate with NPM1. Here we show that the liquid-like properties of NPM1 droplets can be tuned by modulating the extent of electrostatic interactions within the droplet. We propose that a hierarchy of R-motifs, varying in valency and affinity, within nucleolar R-proteins exists which leads to a heterogeneous network of interactions between proteins and rRNA within nucleoli, thus promoting formation of a dynamic liquid-like phase conducive to ribosome biogenesis and other nucleolar functions."],"dc:identifier":["https://dc.uthsc.edu/dissertations/411"],"dc:subject":["Membrane-less organelle","Nucleolus","Phase Separation","Structural Biology","Biological Phenomena, Cell Phenomena, and Immunity","Medical Cell Biology","Medical Sciences","Medicine and Health Sciences"],"dc:title":["The Nucleolar Protein Nucleophosmin Undergoes Liquid-Liquid Phase Separation with Arginine-Rich Nucleolar Proteins through Weak, Multivalent Electrostatic Interactions"],"thesis:degree_discipline":["Biomedical Sciences"],"thesis:degree_level":["Thesis"],"thesis:degree_name":["Master of Science (MS)"]},"updated_at":"2026-07-24T05:00:33Z"}