label: a 3'-end 2',3'-cyclophospho-ribonucleotide-RNA + a 5'-end dephospho-ribonucleoside-RNA => a ribonucleotidyl-ribonucleotide-RNA
label_lc: a 3'-end 2',3'-cyclophospho-ribonucleotide-rna + a 5'-end dephospho-ribonucleoside-rna => a ribonucleotidyl-ribonucleotide-rna