ABSTRACT: The oncogenic microRNA hsa-mir-155-5p targets the transcription factor ELK3 and links it to the hypoxia response and the Hypoxia Inducible Factor HIF1α
Project description:The molecular response to hypoxia is a critical cellular process implicated in cancer, and a target for drug development. The activity of the major player, HIF1α, is regulated at different levels, including the transcriptional level by the Ets factor ELK3. The molecular mechanisms of this intimate transcriptional connection remain largely unknown. Whilst investigating global ELK3-chromatin interactions, we uncovered an unexpected connection that involves the microRNA hsa-miR-155-5p, a hypoxia-inducible oncomir that targets HIF1α. One of the ELK3 chromatin binding sites, detected by Chromatin Immuno-Precipitation Sequencing (ChIP-seq) of normal Human Umbilical Vein Endothelial Cells (HUVEC), is located at the transcription start site of the MIR155HG genes that expresses hsa-miR-155-5p. We confirmed that ELK3 binds to this promoter by ChIP and QPCR. We showed that ELK3 and hsa-miR-155-5p form a double-negative regulatory loop. ELK3 depletion induced hsa-miR-155-5p expression, and hsa-miR-155-5p expression decreased ELK3 expression at the RNA level through a conserved target sequence in its 3’-UTR. We further showed that the activities of hsa-miR-155-5p and ELK3 are functionally linked. Pathway analysis indicates that both factors are implicated in related processes, including cancer and angiogenesis. hsa-miR-155-5p expression and ELK3 depletion have similar effects on expression of known ELK3 target genes, and in-vitro angiogenesis and wound closure. Bioinformatic analysis of cancer RNA-seq data shows that hsa-miR-155-5p and ELK3 expression are significantly anti-correlated, as would be expected from hsa-miR-155-5p targeting ELK3 RNA. Hypoxia (0% oxygen) down-regulates ELK3 mRNA in a microRNA and hsa-miR-155-5p dependent manner. These results tie ELK3 into the hypoxia response pathway through an oncogenic microRNA and into a circuit implicated in the dynamics of the hypoxic response. This crosstalk could be important in the development of new treatments for a range of pathologies.
Project description:The molecular response to hypoxia is a critical cellular process implicated in cancer, and a target for drug development. The activity of the major player, HIF1M-NM-1,M-BM- is regulated at different levels, including the transcriptional level by the Ets factor ELK3. The molecular mechanisms of this intimate transcriptional connection remain largely unknown. Whilst investigating global ELK3-chromatin interactions, we uncovered an unexpected connection that involves the microRNA hsa-miR-155-5p, a hypoxia-inducible oncomir that targets HIF1M-NM-1. One of the ELK3 chromatin binding sites, detected by Chromatin Immuno-Precipitation Sequencing (ChIP-seq) of normal Human Umbilical Vein Endothelial Cells (HUVEC), is located at the transcription start site of the MIR155HG genes that expresses hsa-miR-155-5p. We confirmed that ELK3 binds to this promoter by ChIP and QPCR. We showed that ELK3 and hsa-miR-155-5p form a double-negative regulatory loop. ELK3 depletion induced hsa-miR-155-5p expression, and hsa-miR-155-5p expression decreased ELK3 expression at the RNA level through a conserved target sequence in its 3M-bM-^@M-^Y-UTR. We further showed that the activities of hsa-miR-155-5p and ELK3 are functionally linked. Pathway analysis indicates that both factors are implicated in related processes, including cancer and angiogenesis. hsa-miR-155-5p expression and ELK3 depletion have similar effects on expression of known ELK3 target genes, and in-vitro angiogenesis and wound closure. Bioinformatic analysis of cancer RNA-seq data shows that hsa-miR-155-5p and ELK3 expression are significantly anti-correlated, as would be expected from hsa-miR-155-5p targeting ELK3 RNA. Hypoxia (0% oxygen) down-regulates ELK3 mRNA in a microRNA and hsa-miR-155-5p dependent manner. These results tie ELK3 into the hypoxia response pathway through an oncogenic microRNA and into a circuit implicated in the dynamics of the hypoxic response.M-BM- This crosstalk could be important in the development of new treatments for a range of pathologies. Examination of ELK3 DNA interactions in HUVEC cells under normal oxygen conditions
Project description:LncRNA Hypoxia-inducible factor 1α-antisense 1 (HIF1α-AS1) is located on the antisense strand of the important Hypoxia-inducible factor 1α (HIF1α) gene, but being transcribed in antisense direction along the HIF1α promoter. Here we used the 3’end biotinylated HIF1a-AS1 RNA and a control RNA for RNA Pulldown and searched for interacting proteins in nuclear extracts of human umbilical vein endothelial cells (HUVEC).
Project description:We studied the impact of hsa-miR-139-5p on the protein output by means of an iTRAQ-based approach. First, we established two CAL-62 isogenic cell lines expressing either the mature hsa-miR-139-5p or a non-targeting control upon a doxycycline inducible promoter (PTRE3G-tGFP, Dharmacon). Total proteins of P-tGFP-hsa-miR139-5p untreated or treated with doxycycline (1ug/ml) for 96 and 120 hours were isolated and labeled with iTRAQ® reagent 8-plex. Two independent experiments were performed.
Project description:Adaptation to low levels of O2 (hypoxia) is a universal biological feature across metazoans. Yet the underlying mechanisms how different species sense O2 deprivation remain to be deciphered. Here we functionally characterize a novel long non-coding RNA (lncRNA), LOC105369301, which we termed hypoxia-induced lncRNA for PLK1 stabilization or HILPS. HILPS exhibits appreciable basal expression exclusively in a broad range of human normal and cancer cells and is robustly induced by hypoxia inducible factor 1α (HIF1α). HILPS binds PLK1 and sequesters it from proteasome degradation. Stabilized PLK1 directly phosphorylates HIF1α and enhance its stability, constituting a positive feedforward circuit that reinforces oxygen sensing by HIF1α. HILPS inactivation triggers catastrophic adaptation defect during hypoxia in both normal and cancer cells. These findings introduce a mechanism that underlies the HIF1α identity deeply interconnected with PLK1 integrity, and identify the HILPS-PLK1-HIF1α pathway as a crucial oxygen-sensing axis in regulation of human physiological and pathogenic processes.
Project description:Clear cell renal cell carcinoma (ccRCC), the most common type of renal cancer is often associated with inactivation of the tumor suppressor gene von-Hippel Lindau (VHL), leading to stable expression of hypoxia inducible factors, HIF1α and HIF2α. Although HIF1α functions as a tumor suppressor gene, majority of ccRCCs constitutively express HIF1α, stratifying VHL-deficient ccRCCs into groups which express either both HIF1α and HIF2α (H1H2) or HIF2α exclusively (H2). MicroRNA (miRNA) profiling performed in these two ccRCC subtypes to identify novel molecular mechanisms. ccRCCs were classified into H1H2 and H2 subtypes by immunohostochemical staining of H1F1α and H1F2α expression. Five H1H2 tumor samples and eight H2 tumor samples were used for the study. Matched adjacent normal renal tissues were used as respective controls.
Project description:Hypoxia-inducible factor-1α (HIF1α) attenuates mitochondrial activity while promoting glycolysis. Paradoxically, it remains unknown why lower glycolysis is compromised in human clear cell renal cell carcinomas (ccRCC), in which HIF1α acts a tumor suppressor by inhibiting cell autonomous proliferation. Here we found that unexpectedly, HIF1α suppresses lower glycolysis after the glyceraldehyde 3-phosphate dehydrogenase (GAPDH) step, leading to reduced lactate secretion in different tumor cell types when cells encounter a limited pyruvate supply such as that typically found in the tumor microenvironment in vivo. This is because HIF1α-dependent attenuation of mitochondrial oxygen consumption increases the NADH/NAD+ ratio that suppresses the activity of NADH-sensitive GAPDH glycolytic enzyme. This is manifested when pyruvate supply is limited since pyruvate acts as an electron acceptor that prevents the increment of the NADH/NAD+ ratio. Furthermore, this anti-glycolytic function provides a molecular basis to explain how HIF1α can suppress tumor cell proliferation by increasing the NADH/NAD+ ratio.
Project description:RanBP2 type and C3HC4 type zinc finger containing protein 1 (RBCK1,) is a 58 kDa protein containing N-terminal ubiquitin like (UBL) domain, npl4 type zinc finger (NZF) domain and catalytic carbon terminal RBR domain. It is known that it has abnormal expression in tumors, making it a valuable diagnostic marker and drug target. A large number of studies have confirmed that in ER positive breast cancer, about 25%-40% of the tumor showed a visible hypoxia area. Under hypoxia, tumor cells can activate HIF1 pathway and widely activate the expression of downstream genes. Hypoxia inducible factor HIF-1 is composed of HIF-1α and HIF-1β Two subunits, The protein level of HIF-1α is precisely regulated by oxygen concentration. Here, we report RBCK1, a RING family ubiquitin ligase that regulates HIF1α, promoting ER positive breast cancer growth and inhibiting apoptosis. Deletion of RBCK1 inhibits ER positive breast cancer growth and promotes cell death. RNA sequencing analysis showed that in ER positive breast cancer, RBCK1 may be an important modifier of HIF1α signal pathway. Further experiments showed that RBCK1 and HIF1α Interacts and inhibits HIF1α polyubiquitination to inhibit HIF1α degradation in ER positive breast cancer cells. These finding reveals a novel direct HIF1α regulator and a potential therapeutic target for ER positive breast cancer.
Project description:We analyzed the expression profiles of hsa-miR-145-5p or hsa-miR-31-5p-targeting genes relating to invasion or migration after co-overexpression of hsa-miR-145-5p and 31-5p Gene expression profiles of U87 cells after co-transfection with hsa-miR-145-5p and 31-5p mimics, and U87 cells after transfection miR mimic negative control
Project description:Clear cell renal cell carcinoma (ccRCC), the most common type of renal cancer is often associated with inactivation of the tumor suppressor gene von-Hippel Lindau (VHL), leading to stable expression of hypoxia inducible factors, HIF1α and HIF2α. Although HIF1α functions as a tumor suppressor gene, majority of ccRCCs constitutively express HIF1α, stratifying VHL-deficient ccRCCs into groups which express either both HIF1α and HIF2α (H1H2) or HIF2α exclusively (H2). MicroRNA (miRNA) profiling performed in these two ccRCC subtypes to identify novel molecular mechanisms.