scholarly journals SCFCdc4-mediated Degradation of the Hac1p Transcription Factor Regulates the Unfolded Protein Response inSaccharomyces cerevisiae

2007 ◽  
Vol 18 (2) ◽  
pp. 426-440 ◽  
Author(s):  
Bhupinder Pal ◽  
Nickie C. Chan ◽  
Leon Helfenbaum ◽  
Kaeling Tan ◽  
William P. Tansey ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Unfolded Protein Response ◽  
Rna Polymerase Ii ◽  
Nuclear Localization ◽  
Leucine Zipper ◽  
Nuclear Localization Sequence ◽  
Basic Leucine Zipper ◽  
Unfolded Protein ◽  
Yeast Genes ◽  
Protein Response

The Saccharomyces cerevisiae basic leucine zipper transcription factor Hac1p is synthesized in response to the accumulation of unfolded polypeptides in the lumen of the endoplasmic reticulum (ER), and it is responsible for up-regulation of ∼5% of all yeast genes, including ER-resident chaperones and protein-folding catalysts. Hac1p is one of the most short-lived yeast proteins, having a half-life of ∼1.5 min. Here, we have shown that Hac1p harbors a functional PEST degron and that degradation of Hac1p by the proteasome involves the E2 ubiquitin-conjugating enzyme Ubc3/Cdc34p and the SCFCdc4E3 complex. Consistent with the known nuclear localization of Cdc4p, rapid degradation of Hac1p requires the presence of a functional nuclear localization sequence, which we demonstrated to involve basic residues in the sequence29RKRAKTK35. Two-hybrid analysis demonstrated that the PEST-dependent interaction of Hac1p with Cdc4p requires Ser146 and Ser149. Turnover of Hac1p may be dependent on transcription because it is inhibited in cell mutants lacking Srb10 kinase, a component of the SRB/mediator module of the RNA polymerase II holoenzyme. Stabilization of Hac1p by point mutation or deletion, or as the consequence of defects in components of the degradation pathway, results in increased unfolded protein response element-dependent transcription and improved cell viability under ER stress conditions.

scholarly journals The Unfolded Protein Response Transducer Ire1p Contains a Nuclear Localization Sequence Recognized by Multiple β Importins

2006 ◽  
Vol 17 (12) ◽  
pp. 5309-5323 ◽  
Author(s):  
Laurence Goffin ◽  
Sadanand Vodala ◽  
Christine Fraser ◽  
Joanne Ryan ◽  
Mark Timms ◽  
...  
Keyword(s):  
Unfolded Protein Response ◽  
Nuclear Localization ◽  
Nuclear Localization Sequence ◽  
Binding Studies ◽  
Linker Region ◽  
Unfolded Protein ◽  
Localization Sequence ◽  
The Unfolded Protein Response ◽  
Protein Response

The Ire1p transmembrane receptor kinase/endonuclease transduces the unfolded protein response (UPR) from the endoplasmic reticulum (ER) to the nucleus in Saccharomyces cerevisiae. In this study, we analyzed the capacity of a highly basic sequence in the linker region of Ire1p to function as a nuclear localization sequence (NLS) both in vivo and in vitro. This 18-residue sequence is capable of targeting green fluorescent protein to the nucleus of yeast cells in a process requiring proteins involved in the Ran GTPase cycle that facilitates nuclear import. Mutagenic analysis and importin binding studies demonstrate that the Ire1p linker region contains overlapping potential NLSs: at least one classical NLS (within sequences 642KKKRKR647 and/or 653KKGR656) that is recognized by yeast importin α (Kap60p) and a novel βNLS (646KRGSRGGKKGRK657) that is recognized by several yeast importin β homologues. Kinetic binding data suggest that binding to importin β proteins would predominate in vivo. The UPR, and in particular ER stress-induced HAC1 mRNA splicing, is inhibited by point mutations in the Ire1p NLS that inhibit nuclear localization and also requires functional RanGAP and Ran GEF proteins. The NLS-dependent nuclear localization of Ire1p would thus seem to be central to its role in UPR signaling.

Sequencing of Argonaute-bound miRNA/mRNA hybrids reveals regulation of the unfolded protein response by microRNA-320a

2021 ◽  
Author(s):  
Christopher J Fields ◽  
Lu Li ◽  
Nicholas M Hiers ◽  
Tianqi Li ◽  
Peike Sheng ◽  
...  
Keyword(s):  
Colorectal Cancer ◽  
Er Stress ◽  
Unfolded Protein Response ◽  
Cancer Cells ◽  
Rna Polymerase Ii ◽  
Mirna Biogenesis ◽  
Unfolded Protein ◽  
Colorectal Cancer Cells ◽  
The Unfolded Protein Response ◽  
Protein Response

MicroRNAs (miRNA) are short non-coding RNAs widely implicated in gene regulation. Most metazoan miRNAs utilize the RNase III enzymes Drosha and Dicer for biogenesis. One notable exception is the RNA polymerase II transcription start sites (TSS) miRNAs whose biogenesis does not require Drosha. The functional importance of the TSS-miRNA biogenesis is uncertain. To better understand the function of TSS-miRNAs, we applied a modified Crosslinking, Ligation, and Sequencing of Hybrids on Argonaute (AGO-qCLASH) to identify the targets for TSS-miRNAs in HCT116 colorectal cancer cells with or without DROSHA knockout. We observed that miR-320a hybrids dominate in TSS-miRNA hybrids identified by AGO-qCLASH. Targets for miR-320a are enriched in the eIF2 signaling pathway, a downstream component of the unfolded protein response. Consistently, in miR-320a mimic- and antagomir- transfected cells, differentially expressed genes are enriched in eIF2 signaling. Within the AGO-qCLASH data, we identified the endoplasmic reticulum (ER) chaperone Calnexin as a direct miR-320a target, thus connecting miR-320a to the unfolded protein response. During ER stress, but not amino acid deprivation, miR-320a up-regulates ATF4, a critical transcription factor for resolving ER stress. Our study investigates the targetome of the TSS-miRNAs in colorectal cancer cells and establishes miR-320a as a regulator of unfolded protein response.

scholarly journals Inhibition of IRE1α-mediated XBP1 mRNA cleavage by XBP1 reveals a novel regulatory process during the unfolded protein response

2017 ◽  
Vol 2 ◽  
pp. 36 ◽  
Author(s):  
Fiona Chalmers ◽  
Bernadette Sweeney ◽  
Katharine Cain ◽  
Neil J. Bulleid
Keyword(s):  
Transcription Factor ◽  
Unfolded Protein Response ◽  
Target Genes ◽  
Feedback Mechanism ◽  
Ribonuclease Activity ◽  
Stable Cell Line ◽  
Factor X ◽  
Unfolded Protein ◽  
Xbp1 Mrna ◽  
Protein Response

Background: The mammalian endoplasmic reticulum (ER) continuously adapts to the cellular secretory load by the activation of an unfolded protein response (UPR).  This stress response results in expansion of the ER, upregulation of proteins involved in protein folding and degradation, and attenuation of protein synthesis.  The response is orchestrated by three signalling pathways each activated by a specific signal transducer, either inositol requiring enzyme α (IRE1α), double-stranded RNA-activated protein kinase-like ER kinase (PERK) or activating transcription factor 6 (ATF6).  Activation of IRE1α results in its oligomerisation, autophosphorylation and stimulation of its ribonuclease activity.  The ribonuclease initiates the splicing of an intron from mRNA encoding the transcription factor, X-box binding protein 1 (XBP1), as well as degradation of specific mRNAs and microRNAs. Methods: To investigate the consequence of expression of exogenous XBP1, we generated a stable cell-line expressing spliced XBP1 mRNA under the control of an inducible promotor.  Results: Following induction of expression, high levels of XBP1 protein were detected, which allowed upregulation of target genes in the absence of induction of the UPR.  Remarkably under stress conditions, the expression of exogenous XBP1 repressed splicing of endogenous XBP1 mRNA without repressing the activation of PERK.  Conclusions: These results illustrate that a feedback mechanism exists to attenuate activation of the Ire1α ribonuclease activity in the presence of XBP1.

scholarly journals The Saccharomycescerevisiae Isw2p-Itc1p Complex RepressesINO1 Expression and Maintains Cell Morphology

2001 ◽  
Vol 183 (17) ◽  
pp. 4985-4993 ◽  
Author(s):  
Minetaka Sugiyama ◽  
Jun-Ichi Nikawa
Keyword(s):  
Leucine Zipper ◽  
Suppressor Gene ◽  
Dominant Negative ◽  
Gene Products ◽  
Truncated Form ◽  
Basic Leucine Zipper ◽  
Multicopy Suppressor ◽  
Unfolded Protein ◽  
The Unfolded Protein Response ◽  
Protein Response

ABSTRACT In the yeast Saccharomyces cerevisiae, IRE1 encodes a bifunctional protein with transmembrane kinase and endoribonuclease activities. HAC1 encodes a transcription factor which has a basic leucine zipper domain. Both gene products play a crucial role in the unfolded protein response. Mutants in which one of these genes is defective also show the inositol-auxotrophic (Ino−) phenotype, but the reason for this has not been clear. To investigate the mechanism underlying the Ino−phenotype, we screened a multicopy suppressor gene which can suppress the Ino− phenotype of the Δhac1 strain. We obtained a truncated form of the ITC1 gene that has a defect in its 3′ region. Although the truncated form ofITC1 clearly suppressed the Ino− phenotype of the Δhac1 strain, the full-lengthITC1 had a moderate effect. The gene products ofITC1 and ISW2 are known to constitute a chromatin-remodeling complex (T. Tsukiyama, J. Palmer, C. C. Landel, J. Shiloach, and C. Wu, Genes Dev. 13:686–697, 1999). Surprisingly, the deletion of either ITC1 orISW2 in the Δhac1 strain circumvented the inositol requirement and caused derepression of INO1even under repression conditions, i.e., in inositol-containing medium. These data indicate that the Isw2p-Itc1p complex usually repressesINO1 expression and that overexpression of the truncated form of ITC1 functions in a dominant negative manner inINO1 repression. It is conceivable that the repressor function of this complex is regulated by the C-terminal region of Itc1p.

scholarly journals Palmitate deranges erythropoietin production via transcription factor ATF4 activation of unfolded protein response

2018 ◽  
Vol 94 (3) ◽  
pp. 536-550 ◽  
Author(s):  
Thitinun Anusornvongchai ◽  
Masaomi Nangaku ◽  
Tzu-Ming Jao ◽  
Chia-Hsien Wu ◽  
Yu Ishimoto ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Unfolded Protein Response ◽  
Unfolded Protein ◽  
Erythropoietin Production ◽  
Protein Response

Abstract 3760: Atherogenic Affects Of Arsenic: Role Of Endoplasmic Reticulum Stress And Unfolded Protein Response

Circulation ◽  
2008 ◽  
Vol 118 (suppl_18) ◽  
Author(s):  
Petra Haberzettl ◽  
Elena Vladykovskaya ◽  
Oleg Barski ◽  
Srinivas Sithu ◽  
Stanley D’Souza ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Unfolded Protein Response ◽  
Atherosclerotic Lesion ◽  
The United States ◽  
Hazardous Substance ◽  
Dependent Manner ◽  
Lesion Formation ◽  
Chemical Chaperone ◽  
Unfolded Protein ◽  
Protein Response

Arsenic is a global water contaminant and EPA has listed arsenic as a high priority hazardous substance in the United States. Epidemiological studies suggest that chronic arsenic ingestion increases cardiovascular disease in humans, particularly, carotid atherosclerosis. However, mechanisms of arsenic-induced atherogenesis are unknown. We examined the effect of arsenic exposure on early lesion formation in apoE-null mice maintained on water supplemented with (0, 1, 5 and 50 ppm; 3–16 weeks of age) sodium arsenite. Arsenic, did not affect plasma cholesterol but decreased the triglycerides by 18±4 % (P<0.05). NMR analysis of the lipoproteins showed a significant decrease in the abundance of large VLDL particle (>60 nm diameter). Despite a significant decrease in plasma triglyceride, atherosclerotic lesion formation was significantly increased (2– 4 fold; P<0.05 for all doses) in the aortic sinus and the aortic arch of the arsenic-fed mice in a dose dependent manner. Immunohistochemical analysis showed significant increase in the accumulation of macrophages, expression of MCP-1 and unfolded protein response (UPR) dependent activating transcription factor (ATF)-4 and ATF3, in the lesions of arsenic (1ppm) exposed mice. In vitro , arsenic (5–25 μM), significantly increased the expression of ICAM-1, transmigration of differentiated monocytes and expression of the pro-inflammatory cytokine IL-8 in vascular endothelial cells (vEC). Arsenic, also increased the expression of ER-chaperones Grp 78, HERP and calnexin (2– 6 fold; P<0.01). Examination of the effect of arsenic on UPR showed that arsenic, induced the splicing of IRE-1 dependent, bZIP transcription factor XBP-1(alarm phase) and increased the phosphorylation of eIF2α (PERK mediated adaptive phase) by 3 fold (P<0.01) in vEC. Arsenic also induced the expression of the downstream effecter proteins of eIF2α-ATF3 (8 fold; P<0.01) and pro-apoptotic protein CHOP (4 fold; P<0.01) in vEC. Chemical chaperone, phenyl butyric acid (PBA), attenuated the arsenic-induced expression of ATF3 (>90%; P<0.001) and CHOP (>90%; P<0.001). These data suggest that ER-stress and UPR could exacerbate arsenic-induced vascular inflammation and promote atherogenesis.

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