Project description:Eukaryotic transfer RNAs (tRNA) contain on average 13 modifications that perform a wide range of roles in translation and in the generation of tRNA fragments that regulate gene expression. Queuosine (Q) modification occurs in the wobble anticodon position of tRNAs for amino acids His, Asn, Tyr, and Asp. In eukaryotes, Q modification is fully dependent on diet or on gut microbiome in multi-cellular organisms. Despite decades of study, cellular roles of Q modification remain to be fully elucidated. Here we show that in human cells, Q modification specifically protects its cognate tRNAHis and tRNAAsn against cleavage by ribonucleases. We generated cell lines that contain completely depleted or fully Q-modified tRNAs. Using these resources, we found that Q modification significantly reduces angiogenin cleavage of its cognate tRNAs in vitro. Q modification does not change the cellular abundance of the cognate full-length tRNAs, but alters the cellular content of their fragments in vivo in the absence and presence of stress. Our results provide a new biological aspect of Q modification and a mechanism of how Q modification alters small RNA pool in human cells.
Project description:Mutations in the cytosine-5 RNA methyltransferase NSun2 can cause Intellectual Disability (ID) and symptoms commonly found in patients with Dubowitz syndrome. By analysing gene expression data with the global cytosine-5 RNA methylome in NSun2-deficient mice, we find that loss of cytosine-5 RNA methylation increases the fragmentation of transfer RNAs (tRNA) leading to an accumulation of 5M-bM-^@M-^Y halves. Cleavage of tRNAs by Angiogenin is a common cellular stress response to silence translational programmes, and we show that Angiogenin binds tRNAs lacking site-specific NSun2-methylation with higher affinity. Furthermore, cells lacking functional NSun2 up-regulate stress markers, and deletion of NSun2 compromises cellular survival in response stress stimuli including UV-light and oxidative stress. The decreased tolerance of NSun2 null cells towards oxidative stress can be rescued through inhibition of Angiogenin. In conclusion, cytosine-5 RNA methylation is an essential post-transcriptional mechanism during cellular stress responses and NSun2-mediated tRNA methylation protects from Angiogenin-dependent stress-induced RNA cleavage. RNA Methylation profiling by high throughput sequencing small non-coding RNA profiling by high throughput sequencing Pol III Chromatin-IP profiling by high throughput sequencing
Project description:Gene expression profiling of immortalized human mesenchymal stem cells with hTERT/E6/E7 transfected MSCs. hTERT may change gene expression in MSCs. Goal was to determine the gene expressions of immortalized MSCs.
Project description:Transcriptional profiling of human mesenchymal stem cells comparing normoxic MSCs cells with hypoxic MSCs cells. Hypoxia may inhibit senescence of MSCs during expansion. Goal was to determine the effects of hypoxia on global MSCs gene expression.