BioProject

C/D box small nucleolar RNAs (snoRNAs) transcribed from the DLK1-DIO3 locus are associated with vascular remodelling and cardiovascular disease. None of these snoRNAs has any known targets yet, except for one, AF357425 in mice and SNORD113-6 in humans. We previously showed that this snoRNA targets mRNAs of the integrin signalling pathway and affects arterial fibroblast function. Here, we aimed to identify whether AF357425/SNORD113-6 can also target small RNAs. We overexpressed or inhibited AF357425 in murine fibroblasts and performed small RNA sequencing. Expression of tRNA fragments (tRFs) was predominantly regulated. Compared to overexpression, AF357425 knockdown led to an overall decrease in tRFs, but with an enrichment in smaller tRFs (<30 nucleotides). We focused on tRNA Leucine anti-codon TAA (tRNALeu(TAA)), that has a conserved predicted binding site for AF357425/SNORD113-6. Adjacent to this site, the tRNA is cleaved to form tRFLeu 47-64, in both primary murine fibroblasts and human arterial fibroblasts. We show that AF357425/SNORD113-6 methylates tRNALeu(TAA) and thereby prevents the formation of tRFLeu 47-64. Exposing fibroblasts to oxidative or hypoxic stress, increased AF357425/SNORD113-6 and tRNALeu(TAA) expression, but AF357425/SNORD113-6 knockdown did not lead to an additional formation of tRFLeu 47-64. Thus, independent of cellular stress, AF357425/SNORD113-6 directs site-specific fragmentation of tRNALeu(TAA) via 2’O-ribose-methylation. Overall design: Small RNA-seq on whole cell lysates of primary murine ear cells with AF357425 overexpression (AF357425-High) or inhibition (AF357425-Low)