label: a 5'-end (5'-triphosphoguanosine)-(purine-ribonucleoside) in mRNA + diphosphate => a 5'-end triphospho-(purine-ribonucleoside) in mRNA + GDP + H(+)
label_lc: a 5'-end (5'-triphosphoguanosine)-(purine-ribonucleoside) in mrna + diphosphate => a 5'-end triphospho-(purine-ribonucleoside) in mrna + gdp + h(+)