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