preferred_name: a tRNA with a 3' CC end + 2 diphosphate => a tRNA precursor + 2 CTP
preferred_name_lc: a trna with a 3' cc end + 2 diphosphate => a trna precursor + 2 ctp
label: a tRNA with a 3' CC end + 2 diphosphate => a tRNA precursor + 2 CTP
label_lc: a trna with a 3' cc end + 2 diphosphate => a trna precursor + 2 ctp