label: a 5'-end (5'-methylphospho)-ribonucleoside-RNA + S-adenosyl-L-homocysteine => a 5'-end 5'-phospho-ribonucleoside-RNA + S-adenosyl-L-methionine
label_lc: a 5'-end (5'-methylphospho)-ribonucleoside-rna + s-adenosyl-l-homocysteine => a 5'-end 5'-phospho-ribonucleoside-rna + s-adenosyl-l-methionine