library_construction_protocol: Total RNAs of HeLa cells were isolated using Trizol Reagent, and the mRNA was purified from the total RNA by GenEluteTM mRNA Miniprep Kit. Library preparations were conducted following the NEBNext Ultra II Directional RNA Library Prep Kit for Illumina E7760 manual. For reverse transcription, HIV (Reverse transcriptase recombinant HIV, Worthington Biochemical Corporation, LS05003) was used.