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Global transcriptome changes in HepG2 cells exposed to copper

ABSTRACT: Our hypothesis is that copper modulates the activity of multiple intracellular signal transduction pathways to affect transcription. We have previously shown that copper activates transcription through both metal- and oxidative stress-responsive signal transduction pathways. Since the global molecular mechanisms underlying copper toxicity have not been well elucidated in humans, we have profiled transcriptome changes in HepG2 cells exposed to 100, 200, 400 and 600 uM copper for 4, 8, 12 and 24 hours using a human oligonucleotide microarray. Differentially expressed genes were identified, and integrated into biological and functional pathways through Gene Ontology analysis. Global gene expression profile was overlaid onto biomolecular interaction networks and signal transduction cascades using pathway mapping and interactome identification. Keywords: copper toxicity, HepG2 cells, copper concentrations: 100, 200, 400 and 600 uM, exposure times: 4, 8, 12, and 24 h, expression profiles of copper-responsive genes

ORGANISM(S): Homo sapiens

PROVIDER: GSE9539 | GEO | 2009/06/25

SECONDARY ACCESSION(S): PRJNA103353

REPOSITORIES: GEO

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Project description:Purpose: CsoR, a copper responsive negative regulator of Mycobacterium tuberculosis has been shown to respond to copper and bind to its own regulon in in vitro experiments. Here we examine the role of CsoR in vivo by examining the impact of deletion of csoR on the host transcriptome. Methods: csoR was knocked out of M. tuberculosis H37Rv using the specialized transduction method developed by Bardarov et al (2002), followed by removal of the hygromycin marker with plasmid pYUB870. Both wild type and confirmed csoR knockout were grown in copper free Sauton's media to late log phase before harvesting for transcriptomic studies. RNA was extracted using a modified Trizol method prior to DNAse treatment and rRNA depletion. Sequencing was done on an Illumina HiSeq 2000, filtered for quality using the FASTX-Toolkit, and mapped using Bowtie, and counts per locus generated with BedTools in the Galaxy platform. Differential expression analysis was carried out in edgeR with significantly differentially expressed genes being identified as those with ≥|2| fold differential expression between ΔcsoR and wild type strains, and an FDR < 0.05. Results: We found that 223 genes were differentially expressed between the ΔcsoR and wild type strains, 52 induced and 71 repressed. Differential expression of 10 of these genes, 6 induced and 4 repressed, was confirmed by qRT-PCR using SYBR green methodology. The only copper responsive genes identified were those within the csoR operon: csoR, Rv0968, ctpV, Rv0970, suggesting that csoR may only regulate its own operon in response to copper. Genes in the RicR regulon, another copper responsive transcriptional regulator, were not significantly differentially expressed, but some of these copper inducible genes were slightly down regulated suggesting that copper levels may be lower in the mutant strain as compared to wild type. Notably, 44 of the 48 members of the dosR regulon, responsive to hypoxic and NO stress, were induced in the mutant vs wild type suggesting that csoR is necessary for maintaining homeostasis, likely through copper regulation, within the cell. Conclusions: We have shown that CsoR is likely only directly regulating its own operon in response to copper, however it is required to maintain homeostasis, preventing a hypoxia-type stress response in the absense of copper.

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Global transcriptome changes in HepG2 cells exposed to copper

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