uridine in 25S rRNA + S-adenosyl-L-methionine = N(3)-methyluridine in 25S rRNA + S-adenosyl-L-homocysteine + H(+)
uridine in 25s rrna + s-adenosyl-l-methionine = n(3)-methyluridine in 25s rrna + s-adenosyl-l-homocysteine + h(+)