label: a 5-methyluridine in mRNA + S-adenosyl-L-homocysteine + H(+) => a uridine in mRNA + S-adenosyl-L-methionine
label_lc: a 5-methyluridine in mrna + s-adenosyl-l-homocysteine + h(+) => a uridine in mrna + s-adenosyl-l-methionine