Project description:The purpose of the study was to examine the role of the IRE1a-XBP1 pathway during Th2 lymphocyte activation and differentiation. In vitro Th2 cells were treated with 4μ8c, a drug that specifically inhibits IRE1a endonuclease activity, and transcriptomes were compared.
Project description:The IRE1a-XBP1 pathway, a conserved adaptive response to the unfolded protein response, is indispensable for development of the secretory cells. It maintains endoplasmic reticulum homeostasis by enhancing protein folding and the secretory capacity of the cells. Here, we used a modified ChIP-seq protocol (ChIPmentation) to investigate the genome-wide binding events of the transcription factor XBP1 in differentiated mouse Th2 cells.
Project description:IRE1a and XBP1 are key regulators of the unfolded protein response (UPR). XBP1 ablation causes profound hypolipidemia in mice, and triggers feedback activation of its upstream enzyme IRE1a, instigating regulated IRE1-dependent decay (RIDD), an mRNA degradation mechanism dependent on IRE1a's endoribonuclease activity. Comprehensive microarray analysis of XBP1 and/or IRE1a deficient liver identified genes involved in lipogenesis and lipoprotein metabolism as RIDD substrates, which might contribute to the suppression of plasma lipid levels by activated IRE1a. To identify RIDD substrate mRNAs and direct XBP1 targets in the liver, we performed a comprehensive comparative microarray analysis of three groups of RNA samples: WT and XBP1 deficient mice, WT and IRE1a deficient mice untreated or injected with tunicamycin, and XBP1 deficient mice injected with luciferase or IRE1a siRNA.
Project description:IRE1a and XBP1 are key regulators of the unfolded protein response (UPR). XBP1 ablation causes profound hypolipidemia in mice, and triggers feedback activation of its upstream enzyme IRE1a, instigating regulated IRE1-dependent decay (RIDD), an mRNA degradation mechanism dependent on IRE1a's endoribonuclease activity. Comprehensive microarray analysis of XBP1 and/or IRE1a deficient liver identified genes involved in lipogenesis and lipoprotein metabolism as RIDD substrates, which might contribute to the suppression of plasma lipid levels by activated IRE1a.
Project description:The inositol-requiring enzyme-1a (IRE1a), through its key effector transcription factor X-box binding protein-1 (XBP1), regulates cell fate and malignancy in a tissue and cell-specific manner. Here, we define the transcriptional perturbations associated with induction of XBP1 (encoded by the XBP1S gene generated by IRE1a) eficiency in patient derived human AML cells. Beyond its classical role in activating genes involved in restoring cellular proteostasis during the unfolded protein response (UPR), our transcriptome analysis reveal XBP1-dependent regulation of genes involved in diverse biological processes required for HSC homeostasis and acute myeloid leukemia (AML) development.
Project description:IRE1a is a critical modulator of the unfolded protein response. Its RNAse activity generates the mature transcript for the XBP1 transcription factor and also degrades other ER associated mRNAs in a process termed Regulated IRE1a Dependent mRNA Decay or RIDD. To determine if IRE1a is critical in the response to oncogenic Ras we used ShRNA to knockdown Ire1a or Xbp1 in primary mouse epidermal keratinocytes transduced with a v-HRAS retrovirus.
Project description:The inositol-requiring enzyme-1a (IRE1a), through its key effector transcription factor X-box binding protein-1 (XBP1), regulates cell fate and malignancy in a tissue and cell-specific manner. Here, we define the transcriptional perturbations associated with IRE1a deficiency in normal murine hematopoieitic stem cell (HSC) progenitors and HSC progenitors expressing Flt3 internal tandem duplication (FLT3-ITD) allele, a myeloid leukemia oncogne. Beyond its classical role in activating genes involved in restoring cellular proteostasis during the unfolded protein response (UPR), our transcriptome analysis reveal XBP1-dependent regulation of genes involved in diverse biological processes required for HSC homeostasis and acute myeloid leukemia (AML) development.
Project description:Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has killed over 6 million individuals worldwide and continues to spread in countries where vaccines are not yet widely available, or its citizens are hesitant to become vaccinated. Therefore, it is critical to unravel the molecular mechanisms that allow SARS-CoV-2 and other coronaviruses to infect and overtake the host machinery of human cells. Coronavirus replication triggers endoplasmic reticulum (ER) stress and activation of the unfolded protein response (UPR), a key host cell pathway widely believed essential for viral replication. We examined the master UPR sensor IRE1a kinase/RNase and its downstream transcription factor effector XBP1s, which is processed through an IRE1a-mediated mRNA splicing event, in human lung-derived cells infected with betacoronaviruses. We found human respiratory coronavirus OC43 (HCoV-OC43), Middle East respiratory syndrome coronavirus (MERS-CoV), and murine coronavirus (MHV) all induce ER stress and strongly trigger the kinase and RNase activities of IRE1a as well as XBP1 splicing. In contrast, SARS-CoV-2 only partially activates IRE1a through autophosphorylation, but its RNase activity fails to splice XBP1. Moreover, while IRE1a was dispensable for replication in human cells for all coronaviruses tested, it was required for maximal expression of genes associated with several key cellular functions, including the interferon signaling pathway, during SARS-CoV-2 infection. Our data suggest that SARS-CoV-2 actively inhibits the RNase of autophosphorylated IRE1a, perhaps as a strategy to eliminate detection by the host immune system.