| DNA methyltransferase 2(DNMT2)was originally assigned as a member of the DNA methyltransf-erase family involved in DNA methylation.However,DNA methylation activity of DNMT2 was undetectable or very weak in various species.Goll and his colleagues discovered that DNMT2 is an active RNA methyltransferase that is capable of methylating position C38 of the tRNAAsp in mouse,Arabidopsis thaliana,and Drosophila melanogaster.Zeljko Durdevic reported that DNMT2 is required for efficient innate immune responses in Drosophila.The DNMT2 mutant flies accumulate the levels of Drosophila C virus and activate innate immune responses.However,the role of DNMT2 in mammalian innate immunity is currently not known.The recognition of microbial nucleic acids is a major mechanism used by the immune system to detect pathogens which can cause immune response in the host cell.Therefore,we studied the role of DNMT2 in regulating the DNA-sensing cGAS-STING pathway.We successfully knocked out the DNMT2 gene in AGS?BJ?L929 cells by using the CRISPR/Cas9 technology.Type I interferon,IFN?,can be stimulated by by HT-DNA or cGAMP in the wild type cells,but its expression is reduced in the cells with no DNMT2 expression,suggesting that DNMT2 is required for cGAS-STING-mediated interferon responses.The data from Western blot and immunofluorescence analyses show that the loss of DNMT2 reduces the STING protein expression and affect its cellular distribution.To further explore the underlying mechanism,we tested RNA m6A methylation and the data show that the lack of DNMT2 causes the higher degree of m6A methylation.Wild-type cells and knock-out cells were further infected with Pseudorabies Virus(PRV).The loss of DNMT2 weakens the ability of cells withstanding the viruses and the cells are more likely to die.These results suggest that DNMT2 is essential for cGAS-STING-mediated interferon responses,which may be related to DNMT2 regulation of STING function and the related RNA m6A modification. |
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