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Determinants of Amyloid Formation for the Yeast Termination Factor Nab3

Low complexity protein sequences are often intrinsically unstructured and many have the potential to polymerize into amyloid aggregates including filaments and hydrogels. RNA-binding proteins are unusually enriched in such sequences raising the question as to what function these domains serve in RNA...

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Autores principales: O’Rourke, Thomas W., Reines, Daniel
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Public Library of Science 2016
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4783047/
https://www.ncbi.nlm.nih.gov/pubmed/26954508
http://dx.doi.org/10.1371/journal.pone.0150865
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author O’Rourke, Thomas W.
Reines, Daniel
author_facet O’Rourke, Thomas W.
Reines, Daniel
author_sort O’Rourke, Thomas W.
collection PubMed
description Low complexity protein sequences are often intrinsically unstructured and many have the potential to polymerize into amyloid aggregates including filaments and hydrogels. RNA-binding proteins are unusually enriched in such sequences raising the question as to what function these domains serve in RNA metabolism. One such yeast protein, Nab3, is an 802 amino acid termination factor that contains an RNA recognition motif and a glutamine/proline rich domain adjacent to a region with structural similarity to a human hnRNP. A portion of the C-terminal glutamine/proline-rich domain assembles into filaments that organize into a hydrogel. Here we analyze the determinants of filament formation of the isolated low complexity domain as well as examine the polymerization properties of full-length Nab3. We found that the C-terminal region with structural homology to hnRNP-C is not required for assembly, nor is an adjacent stretch of 16 glutamines. However, reducing the overall glutamine composition of this 134-amino acid segment from 32% to 14% destroys its polymerization ability. Importantly, full-length wildtype Nab3 also formed filaments with a characteristic cross-β structure which was dependent upon the glutamine/proline-rich region. When full length Nab3 with reduced glutamine content in its low complexity domain was exchanged for wildtype Nab3, cells were not viable. This suggests that polymerization of Nab3 is normally required for its function. In an extension of this idea, we show that the low complexity domain of another yeast termination factor, Pcf11, polymerizes into amyloid fibers and a hydrogel. These findings suggest that, like many other RNA binding proteins, termination factors share a common biophysical trait that may be important for their function.
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spelling pubmed-47830472016-03-23 Determinants of Amyloid Formation for the Yeast Termination Factor Nab3 O’Rourke, Thomas W. Reines, Daniel PLoS One Research Article Low complexity protein sequences are often intrinsically unstructured and many have the potential to polymerize into amyloid aggregates including filaments and hydrogels. RNA-binding proteins are unusually enriched in such sequences raising the question as to what function these domains serve in RNA metabolism. One such yeast protein, Nab3, is an 802 amino acid termination factor that contains an RNA recognition motif and a glutamine/proline rich domain adjacent to a region with structural similarity to a human hnRNP. A portion of the C-terminal glutamine/proline-rich domain assembles into filaments that organize into a hydrogel. Here we analyze the determinants of filament formation of the isolated low complexity domain as well as examine the polymerization properties of full-length Nab3. We found that the C-terminal region with structural homology to hnRNP-C is not required for assembly, nor is an adjacent stretch of 16 glutamines. However, reducing the overall glutamine composition of this 134-amino acid segment from 32% to 14% destroys its polymerization ability. Importantly, full-length wildtype Nab3 also formed filaments with a characteristic cross-β structure which was dependent upon the glutamine/proline-rich region. When full length Nab3 with reduced glutamine content in its low complexity domain was exchanged for wildtype Nab3, cells were not viable. This suggests that polymerization of Nab3 is normally required for its function. In an extension of this idea, we show that the low complexity domain of another yeast termination factor, Pcf11, polymerizes into amyloid fibers and a hydrogel. These findings suggest that, like many other RNA binding proteins, termination factors share a common biophysical trait that may be important for their function. Public Library of Science 2016-03-08 /pmc/articles/PMC4783047/ /pubmed/26954508 http://dx.doi.org/10.1371/journal.pone.0150865 Text en © 2016 O’Rourke, Reines http://creativecommons.org/licenses/by/4.0/ This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/) , which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
spellingShingle Research Article
O’Rourke, Thomas W.
Reines, Daniel
Determinants of Amyloid Formation for the Yeast Termination Factor Nab3
title Determinants of Amyloid Formation for the Yeast Termination Factor Nab3
title_full Determinants of Amyloid Formation for the Yeast Termination Factor Nab3
title_fullStr Determinants of Amyloid Formation for the Yeast Termination Factor Nab3
title_full_unstemmed Determinants of Amyloid Formation for the Yeast Termination Factor Nab3
title_short Determinants of Amyloid Formation for the Yeast Termination Factor Nab3
title_sort determinants of amyloid formation for the yeast termination factor nab3
topic Research Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4783047/
https://www.ncbi.nlm.nih.gov/pubmed/26954508
http://dx.doi.org/10.1371/journal.pone.0150865
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