N6-methyladenosine of HIV-1 RNA regulates viral infection and HIV-1 Gag protein expression
Abstract
The internal N6-methyladenosine (m6A) methylation of eukaryotic nuclear RNA controls post-transcriptional gene expression, which is regulated by methyltransferases (writers), demethylases (erasers), and m6A-binding proteins (readers) in cells. The YTH domain family proteins (YTHDF1-3) bind to m6A-modified cellular RNAs and affect RNA metabolism and processing. Here we show that YTHDF1-3 proteins recognize m6A-modified HIV-1 RNA and inhibit HIV-1 infection in cell lines and primary CD4+ T-cells. We further mapped the YTHDF1-3 binding sites in HIV-1 RNA from infected cells. We found that overexpression of YTHDF proteins in cells inhibited HIV-1 infection mainly by decreasing HIV-1 reverse transcription, while knockdown of YTHDF1-3 in cells had the opposite effects. Moreover, silencing the m6A writers decreased HIV-1 Gag protein expression in virus-producer cells, while silencing the m6A erasers increased Gag expression. Our findings suggest an important role of m6A modification of HIV-1 RNA in viral infection and HIV-1 protein synthesis.
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© 2016, Tirumuru et al.
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- Biochemistry and Chemical Biology
- Microbiology and Infectious Disease
Mycofactocin is a redox cofactor essential for the alcohol metabolism of mycobacteria. While the biosynthesis of mycofactocin is well established, the gene mftG, which encodes an oxidoreductase of the glucose-methanol-choline superfamily, remained functionally uncharacterized. Here, we show that MftG enzymes are almost exclusively found in genomes containing mycofactocin biosynthetic genes and are present in 75% of organisms harboring these genes. Gene deletion experiments in Mycolicibacterium smegmatis demonstrated a growth defect of the ∆mftG mutant on ethanol as a carbon source, accompanied by an arrest of cell division reminiscent of mild starvation. Investigation of carbon and cofactor metabolism implied a defect in mycofactocin reoxidation. Cell-free enzyme assays and respirometry using isolated cell membranes indicated that MftG acts as a mycofactocin dehydrogenase shuttling electrons toward the respiratory chain. Transcriptomics studies also indicated remodeling of redox metabolism to compensate for a shortage of redox equivalents. In conclusion, this work closes an important knowledge gap concerning the mycofactocin system and adds a new pathway to the intricate web of redox reactions governing the metabolism of mycobacteria.