Figure 6.

Human METTL1 is a tRNA^Phe methylase. Assays were carried out in triplicate and error bars represent the standard error of the mean. Purified GST, GST-METTL1 and METTL1 (each at 80 nM) were incubated for 15 min with [α-³²P]GTP-labelled pre-tRNA^Phe in the presence of 1 mM SAM. The reactions were terminated by phenol extraction of the tRNA and after complete digestion with P1 nuclease, the m⁷G₄₆ modification was detected after separation from unmodified guanosine by thin-layer chromatography (TLC), followed by phosphorimager analysis and quantification of the % conversion to m⁷G₄₆ (see Materials and methods). (B) Same as panel A, except that only GST-METTL1 was used and the assays were performed for the times indicated.