Fig. 3
From: METTL1 promotes tumorigenesis through tRNA-derived fragment biogenesis in prostate cancer
METTL1 preferentially methylates tRNAs. A tRNAs are the most common RNA species bound to METTL1. Upper panel: Boxplot representing the median Log2 fold change of reads per million (RPM) per transcript bound to METTL1 in PC3 cells. Lower panel: The bar plot shows the total number of unique genes bound to METTL1. B Validation of the lack of METTL1 expression and m7G tRNA methylation in PC3 METTL1 KO cell lines. Western blot of METTL1 (upper panel) and north-dot blot of m7G levels (lower panel). Proteins, long RNAs (> 200 nucleotides), and tRNAs (< 200 nucleotides) were extracted from three independent PC3 METTL1 KO clones and three control clones. Parental PC3 cells are shown. C LC–MS analysis of m7G levels in tRNAs isolated from PC3 METTL1 KO, control, and parental PC3 cells validate the absence of m7G in tRNAs extracted from METTL1 KO cells. Means ± SD are represented (n = 3). D Normalised cleavage signals for the tRNAs AlaAGC and PheGAA in PC3 WT and METTL1 KO cells. Letters on the right show the bases where methylation occurs. E Heatmap showing normalised cleavage values for all tRNAs with guanosines at position 46 in PC3 WT and METTL1 KO cells (n = 2 for each genotype). F tRNA secondary structure showing METTL1-methylated guanines (red circles) in the variable loop. G Graphical summary of tRNA isoacceptors methylated by METTL1 (red) and non-methylated or non-transcribed (grey). Statistical tests: two-tailed Student’s t-test (C). ****p < 0.0001