Exploiting nanopore sequencing advances for tRNA sequencing of human cancer models
tRNAs are important regulators of protein synthesis, and dysregulation of their abundance and modifications status is involved in many human diseases, including cancer. Despite the rapid development of novel tRNA sequencing approaches, due to tRNAs stable secondary structure and abundant modification sites, human tRNA landscape has remained mostly unexplored. Here, we evaluated the new nanopore RNA004 chemistry that is combined with an upgraded Dorado RNA base-caller model for tRNA quantification and site-specific modification determination in human cancer models. We demonstrate that this technology is sensitive to changes in tRNA expression between cancer cell types and response to external stress conditions, with highly reproducible results. We also show that analysis of base-calling error rate confirms the presence of known modifications, among them is the cancer-associated tRNAPhe-Wybutosine modification by TRMT12 (TYW2) . Furthermore, utilizing the new feature of RNA004 chemistry for the detection of common modifications, we show site-specific identification of m5C and pseudouridine at their annotated positions as well as in their known tRNA isoacceptors. We also reveal unique new modification sites and pinpoint a possible limitation of this method in differentiating between m1A and m6A chemical isomers. Overall, RNA004 tRNA-seq has the potential to improve human tRNAome characterization of tRNA abundance and  site-specific modifications simultaneously. Overall design: Human tRNA quantification and modification analysis by Oxford Nanopore Direct RNA sequencing