label: a cytidine in RNA + S-adenosyl-L-methionine => a 5-methylcytidine in RNA + S-adenosyl-L-homocysteine + H(+)
label_lc: a cytidine in rna + s-adenosyl-l-methionine => a 5-methylcytidine in rna + s-adenosyl-l-homocysteine + h(+)