S-adenosyl-L-methionine-dependent methyltransferase that acts as a component of the wyosine derivatives biosynthesis pathway. Probably methylates N-4 position of wybutosine-86 to produce wybutosine-72. 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 Belongs to the TYW3 family.