Phosphorylation and Proteasome Recognition of the mRNA-Binding Protein Cth2 Facilitates Yeast Adaptation to Iron Deficiency

ABSTRACT Iron is an indispensable micronutrient for all eukaryotic organisms due to its participation as a redox cofactor in many metabolic pathways. Iron imbalance leads to the most frequent human nutritional deficiency in the world. Adaptation to iron limitation requires a global reorganization of...

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Autores principales: Antonia M. Romero, Mar Martínez-Pastor, Gang Du, Carme Solé, María Carlos, Sandra V. Vergara, Nerea Sanvisens, James A. Wohlschlegel, David P. Toczyski, Francesc Posas, Eulàlia de Nadal, María T. Martínez-Pastor, Dennis J. Thiele, Sergi Puig
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Publicado: American Society for Microbiology 2018
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spelling oai:doaj.org-article:21975898f8104989b0a38d1dcc665e652021-11-15T15:58:20ZPhosphorylation and Proteasome Recognition of the mRNA-Binding Protein Cth2 Facilitates Yeast Adaptation to Iron Deficiency10.1128/mBio.01694-182150-7511https://doaj.org/article/21975898f8104989b0a38d1dcc665e652018-11-01T00:00:00Zhttps://journals.asm.org/doi/10.1128/mBio.01694-18https://doaj.org/toc/2150-7511ABSTRACT Iron is an indispensable micronutrient for all eukaryotic organisms due to its participation as a redox cofactor in many metabolic pathways. Iron imbalance leads to the most frequent human nutritional deficiency in the world. Adaptation to iron limitation requires a global reorganization of the cellular metabolism directed to prioritize iron utilization for essential processes. In response to iron scarcity, the conserved Saccharomyces cerevisiae mRNA-binding protein Cth2, which belongs to the tristetraprolin family of tandem zinc finger proteins, coordinates a global remodeling of the cellular metabolism by promoting the degradation of multiple mRNAs encoding highly iron-consuming proteins. In this work, we identify a critical mechanism for the degradation of Cth2 protein during the adaptation to iron deficiency. Phosphorylation of a patch of Cth2 serine residues within its amino-terminal region facilitates recognition by the SCFGrr1 ubiquitin ligase complex, accelerating Cth2 turnover by the proteasome. When Cth2 degradation is impaired by either mutagenesis of the Cth2 serine residues or deletion of GRR1, the levels of Cth2 rise and abrogate growth in iron-depleted conditions. Finally, we uncover that the casein kinase Hrr25 phosphorylates and promotes Cth2 destabilization. These results reveal a sophisticated posttranslational regulatory pathway necessary for the adaptation to iron depletion. IMPORTANCE Iron is a vital element for many metabolic pathways, including the synthesis of DNA and proteins, and the generation of energy via oxidative phosphorylation. Therefore, living organisms have developed tightly controlled mechanisms to properly distribute iron, since imbalances lead to nutritional deficiencies, multiple diseases, and vulnerability against pathogens. Saccharomyces cerevisiae Cth2 is a conserved mRNA-binding protein that coordinates a global reprogramming of iron metabolism in response to iron deficiency in order to optimize its utilization. Here we report that the phosphorylation of Cth2 at specific serine residues is essential to regulate the stability of the protein and adaptation to iron depletion. We identify the kinase and ubiquitination machinery implicated in this process to establish a posttranscriptional regulatory model. These results and recent findings for both mammals and plants reinforce the privileged position of E3 ubiquitin ligases and phosphorylation events in the regulation of eukaryotic iron homeostasis.Antonia M. RomeroMar Martínez-PastorGang DuCarme SoléMaría CarlosSandra V. VergaraNerea SanvisensJames A. WohlschlegelDavid P. ToczyskiFrancesc PosasEulàlia de NadalMaría T. Martínez-PastorDennis J. ThieleSergi PuigAmerican Society for Microbiologyarticleiron deficiencyphosphorylationposttranslational regulationprotein stabilityyeastMicrobiologyQR1-502ENmBio, Vol 9, Iss 5 (2018)
institution DOAJ
collection DOAJ
language EN
topic iron deficiency
phosphorylation
posttranslational regulation
protein stability
yeast
Microbiology
QR1-502
spellingShingle iron deficiency
phosphorylation
posttranslational regulation
protein stability
yeast
Microbiology
QR1-502
Antonia M. Romero
Mar Martínez-Pastor
Gang Du
Carme Solé
María Carlos
Sandra V. Vergara
Nerea Sanvisens
James A. Wohlschlegel
David P. Toczyski
Francesc Posas
Eulàlia de Nadal
María T. Martínez-Pastor
Dennis J. Thiele
Sergi Puig
Phosphorylation and Proteasome Recognition of the mRNA-Binding Protein Cth2 Facilitates Yeast Adaptation to Iron Deficiency
description ABSTRACT Iron is an indispensable micronutrient for all eukaryotic organisms due to its participation as a redox cofactor in many metabolic pathways. Iron imbalance leads to the most frequent human nutritional deficiency in the world. Adaptation to iron limitation requires a global reorganization of the cellular metabolism directed to prioritize iron utilization for essential processes. In response to iron scarcity, the conserved Saccharomyces cerevisiae mRNA-binding protein Cth2, which belongs to the tristetraprolin family of tandem zinc finger proteins, coordinates a global remodeling of the cellular metabolism by promoting the degradation of multiple mRNAs encoding highly iron-consuming proteins. In this work, we identify a critical mechanism for the degradation of Cth2 protein during the adaptation to iron deficiency. Phosphorylation of a patch of Cth2 serine residues within its amino-terminal region facilitates recognition by the SCFGrr1 ubiquitin ligase complex, accelerating Cth2 turnover by the proteasome. When Cth2 degradation is impaired by either mutagenesis of the Cth2 serine residues or deletion of GRR1, the levels of Cth2 rise and abrogate growth in iron-depleted conditions. Finally, we uncover that the casein kinase Hrr25 phosphorylates and promotes Cth2 destabilization. These results reveal a sophisticated posttranslational regulatory pathway necessary for the adaptation to iron depletion. IMPORTANCE Iron is a vital element for many metabolic pathways, including the synthesis of DNA and proteins, and the generation of energy via oxidative phosphorylation. Therefore, living organisms have developed tightly controlled mechanisms to properly distribute iron, since imbalances lead to nutritional deficiencies, multiple diseases, and vulnerability against pathogens. Saccharomyces cerevisiae Cth2 is a conserved mRNA-binding protein that coordinates a global reprogramming of iron metabolism in response to iron deficiency in order to optimize its utilization. Here we report that the phosphorylation of Cth2 at specific serine residues is essential to regulate the stability of the protein and adaptation to iron depletion. We identify the kinase and ubiquitination machinery implicated in this process to establish a posttranscriptional regulatory model. These results and recent findings for both mammals and plants reinforce the privileged position of E3 ubiquitin ligases and phosphorylation events in the regulation of eukaryotic iron homeostasis.
format article
author Antonia M. Romero
Mar Martínez-Pastor
Gang Du
Carme Solé
María Carlos
Sandra V. Vergara
Nerea Sanvisens
James A. Wohlschlegel
David P. Toczyski
Francesc Posas
Eulàlia de Nadal
María T. Martínez-Pastor
Dennis J. Thiele
Sergi Puig
author_facet Antonia M. Romero
Mar Martínez-Pastor
Gang Du
Carme Solé
María Carlos
Sandra V. Vergara
Nerea Sanvisens
James A. Wohlschlegel
David P. Toczyski
Francesc Posas
Eulàlia de Nadal
María T. Martínez-Pastor
Dennis J. Thiele
Sergi Puig
author_sort Antonia M. Romero
title Phosphorylation and Proteasome Recognition of the mRNA-Binding Protein Cth2 Facilitates Yeast Adaptation to Iron Deficiency
title_short Phosphorylation and Proteasome Recognition of the mRNA-Binding Protein Cth2 Facilitates Yeast Adaptation to Iron Deficiency
title_full Phosphorylation and Proteasome Recognition of the mRNA-Binding Protein Cth2 Facilitates Yeast Adaptation to Iron Deficiency
title_fullStr Phosphorylation and Proteasome Recognition of the mRNA-Binding Protein Cth2 Facilitates Yeast Adaptation to Iron Deficiency
title_full_unstemmed Phosphorylation and Proteasome Recognition of the mRNA-Binding Protein Cth2 Facilitates Yeast Adaptation to Iron Deficiency
title_sort phosphorylation and proteasome recognition of the mrna-binding protein cth2 facilitates yeast adaptation to iron deficiency
publisher American Society for Microbiology
publishDate 2018
url https://doaj.org/article/21975898f8104989b0a38d1dcc665e65
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