design: RNA oligonucleotides, including all 18 DRACH motifs and 68 non-DRACH motifs, were chemically synthesized. A ~1 kb sequence with T7 polymerase promoter was synthesized and cloned into the pBHA vector using blunt-end EcoRI by Bioneer. In vitro transcription was conducted using HiScribe T7 High Yield RNA Synthesis Kit (NEB, E2040S), using 500 ng of EcoRI-treated, linearized DNA, following the manufacturer's protocol. The RNA was generated using rNTPs besides rATP, which was substituted with N6-methyladenosine-5-triphosphate (m6ATP) (Trilink, N-1013-1). Following DNase I treatment, IVT RNA was purified using a 5% TBE-Urea gel (National Diagnostics), eluted with 3x volume of 300 mM NaCl buffer overnight at 4 C, and recovered with the Oligo Clean & Concentrator (Zymo Research, D4061). Polyadenylation was performed using E-PAP Poly(A) Tailing Kit (Thermo Fisher Scientific, AM1350), following the optimized protocol. Poly(A)-tailed RNAs were purified with Dynabeads Oligo(dT)25 (Invitrogen, 61002) following the manufacturer's protocol. The DRS sequencing library was prepared from 500 ng of poly(A)-tailed RNA using SQK-RNA004 sequencing kit (ONT), following the manufacturer's protocol. Samples were loaded onto the primed PromethION RNA flow cell (ONT, FLO-PRO004RA). The direct RNA sequencing(DRS) was performed by PromethION 2 Solo device (ONT).  The DRS sequencing data were basecalled with Dorado (ver. 0.7.3) with rna004_130bps_sup@v5.0.0 basecalling model and options dorado basecaller --reference --chunksize 12000 --min-qscore 0 --emit-moves --estimate-poly-a. BAM files generated by Dorado were converted to FASTQ format using SAMTools (ver. 1.22.1).