ABSTRACT
N6-Methyldeoxyadenine (6mA) has been rediscovered as a DNA modification with potential biological function in metazoans. However, the physiological function and regulatory mechanisms regarding the establishment, maintenance and removal of 6mA in eukaryotes are still poorly understood. Here we show that genomic 6mA levels change in response to pathogenic infection in Caenorhabditis elegans (C. elegans). We further identify METL-9 as the methyltransferase that catalyzes DNA 6mA modifications upon pathogen infection. Deficiency of METL-9 impairs the induction of innate immune response genes and renders the animals more susceptible to pathogen infection. Interestingly, METL-9 functions through both 6mA-dependent and -independent mechanisms to transcriptionally regulate innate immunity. Our findings reveal that 6mA is a functional DNA modification in immunomodulation in C. elegans.
Subject(s)
Caenorhabditis elegans Proteins , Caenorhabditis elegans , Animals , Caenorhabditis elegans/genetics , Methyltransferases/genetics , DNA Methylation , DNA/genetics , Immunity, Innate , Caenorhabditis elegans Proteins/genetics , Caenorhabditis elegans Proteins/metabolismABSTRACT
The mTOR complex 1 (mTORC1) controls cell growth in response to amino acid levels1. Here we report SAR1B as a leucine sensor that regulates mTORC1 signalling in response to intracellular levels of leucine. Under conditions of leucine deficiency, SAR1B inhibits mTORC1 by physically targeting its activator GATOR2. In conditions of leucine sufficiency, SAR1B binds to leucine, undergoes a conformational change and dissociates from GATOR2, which results in mTORC1 activation. SAR1B-GATOR2-mTORC1 signalling is conserved in nematodes and has a role in the regulation of lifespan. Bioinformatic analysis reveals that SAR1B deficiency correlates with the development of lung cancer. The silencing of SAR1B and its paralogue SAR1A promotes mTORC1-dependent growth of lung tumours in mice. Our results reveal that SAR1B is a conserved leucine sensor that has a potential role in the development of lung cancer.
Subject(s)
Leucine/metabolism , Mechanistic Target of Rapamycin Complex 1/metabolism , Monomeric GTP-Binding Proteins/metabolism , Signal Transduction , Animals , Caenorhabditis elegans/genetics , Caenorhabditis elegans/metabolism , Caenorhabditis elegans/physiology , Caenorhabditis elegans Proteins/genetics , Caenorhabditis elegans Proteins/metabolism , Conserved Sequence , GTP Phosphohydrolases/genetics , GTP Phosphohydrolases/metabolism , HEK293 Cells , Humans , Leucine/deficiency , Longevity/genetics , Lung Neoplasms/genetics , Lung Neoplasms/metabolism , Mechanistic Target of Rapamycin Complex 1/agonists , Mice , Monomeric GTP-Binding Proteins/chemistry , Monomeric GTP-Binding Proteins/deficiency , Monomeric GTP-Binding Proteins/genetics , Multiprotein Complexes/metabolism , Nuclear Proteins/metabolism , Protein Binding , Tumor Suppressor Proteins/metabolism , Xenograft Model Antitumor AssaysABSTRACT
Ethylene is an important phytohormone that promotes the ripening of fruits and senescence of flowers thereby reducing their shelf lives. Specific ethylene biosynthesis inhibitors would help to decrease postharvest loss. Here, we identify pyrazinamide (PZA), a clinical drug used to treat tuberculosis, as an inhibitor of ethylene biosynthesis in Arabidopsis thaliana, using a chemical genetics approach. PZA is converted to pyrazinecarboxylic acid (POA) in plant cells, suppressing the activity of 1-aminocyclopropane-1-carboxylic acid oxidase (ACO), the enzyme catalysing the final step of ethylene formation. The crystal structures of Arabidopsis ACO2 in complex with POA or 2-Picolinic Acid (2-PA), a POA-related compound, reveal that POA/2-PA bind at the active site of ACO, preventing the enzyme from interacting with its natural substrates. Our work suggests that PZA and its derivatives may be promising regulators of plant metabolism, in particular ethylene biosynthesis.
