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The unfolded protein response regulator ATF6 promotes mesodermal differentiation.

ABSTRACT: ATF6 encodes a transcription factor that is anchored in the endoplasmic reticulum (ER) and activated during the unfolded protein response (UPR) to protect cells from ER stress. Deletion of the isoform activating transcription factor 6? (ATF6?) and its paralog ATF6? results in embryonic lethality and notochord dysgenesis in nonhuman vertebrates, and loss-of-function mutations in ATF6? are associated with malformed neuroretina and congenital vision loss in humans. These phenotypes implicate an essential role for ATF6 during vertebrate development. We investigated this hypothesis using human stem cells undergoing differentiation into multipotent germ layers, nascent tissues, and organs. We artificially activated ATF6 in stem cells with a small-molecule ATF6 agonist and, conversely, inhibited ATF6 using induced pluripotent stem cells from patients with ATF6 mutations. We found that ATF6 suppressed pluripotency, enhanced differentiation, and unexpectedly directed mesodermal cell fate. Our findings reveal a role for ATF6 during differentiation and identify a new strategy to generate mesodermal tissues through the modulation of the ATF6 arm of the UPR.

SUBMITTER: Kroeger H

PROVIDER: S-EPMC5957084 | biostudies-literature | 2018 Feb

REPOSITORIES: biostudies-literature

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The unfolded protein response regulator ATF6 promotes mesodermal differentiation.

Kroeger Heike H Grimsey Neil N Paxman Ryan R Chiang Wei-Chieh WC Plate Lars L Jones Ying Y Shaw Peter X PX Trejo JoAnn J Tsang Stephen H SH Powers Evan E Kelly Jeffery W JW Wiseman R Luke RL Lin Jonathan H JH

Science signaling 20180213 517

<i>ATF6</i> encodes a transcription factor that is anchored in the endoplasmic reticulum (ER) and activated during the unfolded protein response (UPR) to protect cells from ER stress. Deletion of the isoform activating transcription factor 6α (ATF6α) and its paralog ATF6β results in embryonic lethality and notochord dysgenesis in nonhuman vertebrates, and loss-of-function mutations in ATF6α are associated with malformed neuroretina and congenital vision loss in humans. These phenotypes implicate ...[more]

PMID: 29440509

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Project description:The Unfolded Protein Response (UPR) is a cascade of intracellular stress signaling from the endoplasmic reticulum (ER) that protect the cells from the stress caused by accumulation of unfolded or misfolded proteins in the ER. Activating transcription factor 6 (ATF6) is one of primary UPR transducers that remodels the stressed cells through transcriptional regulation. Although the activation mechanism and biological roles of ATF6 have been well studied, the understanding of the negative or feedback regulation of ATF6 remains elusive. In this report, we showed that ATF6 protein can be modified by small ubiquitin-like modification (SUMOylation) and that the transcriptional activity of ATF6 is negatively regulated by SUMOylation. We identified that SUMOylation of ATF6 is significantly increased in the cells expressing misfolded cystic fibrosis transmembrane conductance regulator (CFTR) encoded by the mutant human CFTR gene (dF508CFTR). Further analyses revealed two highly conserved SUMOylation motifs within the trans-activation domain of ATF6 protein of human, mouse, or rat specie. The human ATF6 protein can be SUMOylated mediated through the small ubiquitin-like modifier protein 1 (SUMO-1) and E3 SUMO-protein ligase 1 (PIAS1) at the conserved sumoylation residue Lys149 that is located at the N-terminal of the activated form of ATF6 protein. Bimolecular fluorescence complementation (BiFC) analysis confirmed that the activated ATF6 protein can be SUMOylated and that the ATF6 sumoylation occurs in the nuclei. Moreover, trans-activation reporter analysis demonstrated that SUMOylation of the ATF6 protein at the conserved residue Lys149 represses the transcriptional activity of ATF6. In summary, our study revealed a negative regulation of the UPR transducer ATF6 through post-translational SUMOylation. The information from this study will not only increase our understanding of the fine-tuning regulation of the UPR signaling but will also be informative to the modulation of the UPR for therapeutic benefits.

Dataset Information

The unfolded protein response regulator ATF6 promotes mesodermal differentiation.

Publications

The unfolded protein response regulator ATF6 promotes mesodermal differentiation.

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