S-adenosyl-L-methionine-dependent transferase that acts as a component of the wybutosine biosynthesis pathway. Wybutosine is a hyper modified guanosine with a tricyclic base found at the 3'-position adjacent to the anticodon of eukaryotic phenylalanine tRNA (By similarity). 4-demethyl-7-[(3S)-3-amino-3-carboxypropyl]wyosine(37) in tRNA(Phe) + S-adenosyl-L-methionine = 7-[(3S)-3-amino-3-carboxypropyl]wyosine(37) in tRNA(Phe) + H(+) + S-adenosyl-L-homocysteine 4-demethylwyosine(37) in tRNA(Phe) + S-adenosyl-L-methionine = 4-demethyl-7-[(3S)-3-amino-3-carboxypropyl]wyosine(37) in tRNA(Phe) + H(+) + S-methyl-5'-thioadenosine tRNA modification; wybutosine-tRNA(Phe) biosynthesis. In the C-terminal section; belongs to the class I-like SAM-binding methyltransferase superfamily. TRM5/TYW2 family. In the N-terminal section; belongs to the TYW3 family. In plants, methylation steps 2, 3 and 4 of wybutosine biosynthesis are probably processed by the this multifunctional enzyme, while in other eukaryotes, these steps are mediated by 3 different proteins.