Project description:To investigate selectivity of mRNA oxidation, total RNA and oxidized RNA isolated from Neuro 2a cells before and after H2O2 treatment were employed for microarray analysis. It was found that selective oxidation of mRNA already occurs under normal culture conditions but was increased by H2O2, especially in a subset of mRNAs related to certain functions. Moreover, mRNA oxidation level is also related to its abundance or stability (half-life time). This shows for the first time that mRNA oxidation is associated with RNA homeostasis including function, stability and abundance depending on cellular redox status in a genome-wide scale.
Project description:To investigate selectivity of mRNA oxidation, total RNA and oxidized RNA isolated from Neuro 2a cells before and after H2O2 treatment were employed for microarray analysis. It was found that selective oxidation of mRNA already occurs under normal culture conditions but was increased by H2O2, especially in a subset of mRNAs related to certain functions. Moreover, mRNA oxidation level is also related to its abundance or stability (half-life time). This shows for the first time that mRNA oxidation is associated with RNA homeostasis including function, stability and abundance depending on cellular redox status in a genome-wide scale. Neuro 2a cells received hydrogen peroxide treatment or no treatment as a control. Samples were applied for RNA extraction and ARP labeling, which could bind with apurinic/apyrimidinic sites, and then a pull-down process to isolate oxidized RNA. Total RNA and oxidized RNA were used for subsequent transcriptomic profiling. 4 types of samples were analyzed: Basal-total: untreated N2a cells labeled with ARP, but not processed for the pull-down assay. Ox-total: hydrogen peroxide-treated N2a cells labeled with ARP, but not processed for the pull-down assay. Basal-ARP: untreated N2a cells labeled with ARP, and processed for the pull-down assay. ARP-derivatized RNA, which is also oxidized RNA, was concentrated and used for the microarray analysis. Ox-ARP: hydrogen peroxide-treated N2a cells labeled with ARP, and processed for the pull-down assay. ARP-derivatized RNA, which is also oxidized RNA, was concentrated and used for the microarray analysis.
Project description:Anaerobic activation of benzene is expected to represent a novel biochemistry of environmental significance but research into the mechanisms has been stymied by a lack of a genetically tractable pure culture which unequivocally does not use molecular oxygen to activate benzene. Geobacter metallireducens grew in a medium in which benzene was the sole electron donor and Fe(III) was the sole electron acceptor with a stoichiometry of benzene loss and Fe(III) reduction consistent with benzene oxidation to carbon dioxide coupled with Fe(III) reduction. Phenol labeled with 18O was produced when the medium was labeled with H218O, as expected for a true anaerobic conversion of benzene to phenol. Gene expression patterns indicated that benzene was metabolized through a phenol intermediate rather than benzoate or toluene. Deletion of ppcB, which encodes a subunit of the phenylphosphate carboxylase, an enzyme required for phenol metabolism, inhibited metabolism of benzene. Deleting genes specific for benzoate or toluene metabolism did not. Comparison of gene expression patterns in cells grown on benzene versus cells grown on phenol revealed genes specifically expressed in benzene-grown cells. Deletion of one of these, Gmet_3376, inhibited anaerobic benzene oxidation, but not the metabolism of phenol, benzoate, or toluene. The availability of a genetically tractable pure culture that can anaerobically convert benzene to phenol with oxygen derived from water should significantly accelerate elucidation of the mechanisms by which benzene can be activated in the absence of molecular oxygen. Total RNA from three separate cultures of G. metallireducens grown with 250 µM benzene three separate cultures of G. metallireducens grown with 500 µM phenol three separate cultures of G. metallireducens grown with 1 mM benzoate three separate cultures of G. metallireducens grown with 500 µM toluene three separate cultures of G. metallireducens grown with 10 mM acetate were used to study [1] Anaerobic oxidation of benzene by G. metallireducens (Benzene vs. acetate, Benzene vs. benzoate, Benzene vs. phenol, Benzene vs. toluene) [2] Anaerobic oxidation of benzoate by G. metallireducens (Benzoate vs. acetate) [3] Anaerobic oxidation of phenol by G. metallireducens (Phenol vs. acetate) [4] Anaerobic oxidation of toluene by G. metallireducens (Toluene vs. acetate) Each chip measures the expression level of 3,627 genes from G. metallireducens DSM 7210 with nine 45-60-mer probe pairs (PM/MM) per gene, with three-fold technical redundancy.
Project description:Investigation of whole genome gene expression level changes in anaerobic, nitrate-dependent Fe(II) oxidation in the chemolithoautotrophic bacterium Thiobacillus denitrificans Here we report on a study to identify genes associated with nitrate-dependent Fe(II) oxidation by whole-genome transcriptional (microarray) assays including the use of FeCO3, Fe2+, and U(IV) oxides as electron donors under denitrifying conditions. A 25 chip study using total RNA recovered from wild-type T. denitrificans was cultivated at 30oC under strictly anaerobic conditions with growth medium that contained 20 mM thiosulfate, 20 mM nitrate, and 30 mM bicarbonate (pH ~7) and exposed to 8 treatments. Each chip measures the expression level of 2832 ORFs with N 24-mer probe pairs (PM/MM) per gene, with three-fold technical redundancy.
Project description:Cellular senescence is a stress-induced irreversible cell cycle arrest involved in tumor suppression and aging. Many stresses, such as telomere shortening and oncogene activation, induce senescence by damaging nuclear DNA. However, the mechanisms linking DNA damage to senescence remain unclear. Here, we show that DNA damage response (DDR) signaling to mitochondria triggers senescence. A genome-wide siRNA screen implicated the outer mitochondrial transmembrane protein BNIP3 in senescence induction. We found that BNIP3 is a substrate of the DDR kinase ATM and contributes to an increase in the number of mitochondrial cristae upon DNA damage. Stable isotope labeling metabolomics indicated that this increase in cristae enhances the oxidation of fatty acids to acetyl-CoA. Notably, pharmacological activation of fatty acid oxidation alone induced senescence both in vitro and in vivo. Our findings suggest that mitochondrial energy metabolism plays a critical role in senescence induction and is a potential intervention target to control senescence.
Project description:Apurinic/apyrimidinic (AP) sites are a class of highly mutagenic and toxic DNA lesions arising in the genome from a number of exogenous and endogenous sources. Repair of AP lesions takes place predominantly by the base excision pathway (BER). However, among chemically heterogeneous AP lesions formed in DNA, some are resistant to the endonuclease APE1 and thus refractory to BER. Here, we employed two types of reporter constructs accommodating synthetic APE1-resistant AP lesions to investigate the auxiliary repair mechanisms in human cells. By combined analyses of recovery of the transcription rate and suppression of transcriptional mutagenesis at specifically positioned AP lesions, we demonstrate that nucleotide excision repair pathway (NER) efficiently removes BER-resistant AP lesions and significantly enhances the repair of APE1-sensitive ones. Our results further indicate that core NER components XPA and XPF are equally required and that both global genome (GG-NER) and transcription coupled (TC-NER) subpathways contribute to the repair.
Project description:Mitochondrial DNA (mtDNA) modifications play an emerging role in innate immunity and inflammatory diseases. Nonetheless, relatively little is known regarding the locations of mtDNA modifications. Such information is critically important for deciphering their roles in mtDNA instability, mtDNA-mediated immune and inflammatory responses, and mitochondrial disorders. The affinity probe-based enrichment of lesion-containing DNA represents a key strategy for sequencing DNA modifications. Existing methods are limited in the enrichment specificity of abasic (AP) sites, a prevalent DNA modification and repair intermediate. Herein, we devise a novel approach, termed dual chemical labeling-assisted sequencing (DCL-seq), for mapping AP sites. DCL-seq features two designer compounds for enriching and mapping AP sites specifically at single-nucleotide resolution. For proof of principle, we mapped AP sites in mtDNA from HeLa cells under different biological conditions. The resulting AP site maps coincide with mtDNA regions with low TFAM (mitochondrial transcription factor A) coverage and with potential G-quadruplex-forming sequences. In addition, we demonstrated the broader applicability of the method in sequencing other DNA modifications in mtDNA, such as N7-methyl-2'-deoxyguanosine and N3-methyl-2'-deoxyadenosine, when coupled with a lesion-specific repair enzyme. Together, DCL-seq holds the promise to sequence multiple DNA modifications in various biological samples.