design: RNA is reverse transcribed into cDNA using Invitrogen SuperScript II RT. Double-stranded synthesis is performed with E. coli DNA polymerase I and RNase H, incorporating dUTP and blunting the ends. A base is added to both ends for adapter ligation. The fragments are purified using magnetic beads and digested with UDG enzyme. PCR is performed with cycles: 95C for 3 min, 98C for 15s, 60C for 15s, 72C for 30s, followed by a final extension at 72C for 5 min to create a 300 bp  50 bp library.