Fig. 1: WDR4 promotes the tRNA N7-methylguanosine methyltransferase activity of METTL1.
a Relative methyltransferase activity of METTL1, WDR4 and the METTL1–WDR4 complex. b Schematic domain structures of METTL1 and WDR4. The truncated regions for crystallization of METTL1 and WDR4 are represented by dashed lines. c Overall structure of the METTL1–WDR4 heterodimer. Dashed lines indicate residues with missing electron density. d Close-up view of the interface of METTL1 and WDR4. Residues forming the interface of METTL1 and WDR4 are shown as cyan and green sticks, respectively. Dashed lines represent hydrogen bonds. e Schematic representation of the interactions between R170 on WDR4 and other residues on METTL1 (cyan) and WDR4 (green). Water is shown as a red ball. f Superimposition of the WDR4-bound (cyan), SAM-bound (yellow, PDB: 3CKK) and apo (pink, alphafold2 predicted) structures of METTL1. SAM is shown as yellow sticks. g Close-up view of the conformational change regions shown in f. h ITC measurement of the binding affinity between SAM and METTL1, the METTL1–WDR4 complex and WDR4. i Electrostatic surface of the METTL1–WDR4 complex with the potential RNA-binding surface marked by a dashed circle. Blue, white, and red represent positive, neutral, and negative surfaces, respectively. j, k EMSA analysis of the interaction between tRNAphe and proteins. *indicates free tRNAphe. l The proposed mechanism by which WDR4 promotes the methyltransferase activity of METTL1. Dashed arrows indicate the dynamics of the tRNA.
