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RNA. 2015 Sep;21(9):1532-43. doi: 10.1261/rna.051524.115. Epub 2015 Jul 9.

NSUN6 is a human RNA methyltransferase that catalyzes formation of m5C72 in specific tRNAs.

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Centre for Biochemistry and Molecular Cell Biology, Georg-August-University, 37073 Göttingen, Germany.
Institute for Organic and Biomolecular Chemistry, Georg-August-University, 37077 Göttingen, Germany.
Centre for Biochemistry and Molecular Cell Biology, Georg-August-University, 37073 Göttingen, Germany Göttingen Centre for Molecular Biosciences, Georg-August-University, 37073 Göttingen, Germany.


Many cellular RNAs require modification of specific residues for their biogenesis, structure, and function. 5-methylcytosine (m(5)C) is a common chemical modification in DNA and RNA but in contrast to the DNA modifying enzymes, only little is known about the methyltransferases that establish m(5)C modifications in RNA. The putative RNA methyltransferase NSUN6 belongs to the family of Nol1/Nop2/SUN domain (NSUN) proteins, but so far its cellular function has remained unknown. To reveal the target spectrum of human NSUN6, we applied UV crosslinking and analysis of cDNA (CRAC) as well as chemical crosslinking with 5-azacytidine. We found that human NSUN6 is associated with tRNAs and acts as a tRNA methyltransferase. Furthermore, we uncovered tRNA(Cys) and tRNA(Thr) as RNA substrates of NSUN6 and identified the cytosine C72 at the 3' end of the tRNA acceptor stem as the target nucleoside. Interestingly, target recognition in vitro depends on the presence of the 3'-CCA tail. Together with the finding that NSUN6 localizes to the cytoplasm and largely colocalizes with marker proteins for the Golgi apparatus and pericentriolar matrix, our data suggest that NSUN6 modifies tRNAs in a late step in their biogenesis.


5-methylcytosine; NSUN protein; RNA modification; methyltransferase; tRNA

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