title: CO
design: The rRNA and linear RNA of RNA sample were depleted.First strand cDNA was synthesized using random hexamer primer and M-MuLV Reverse Transcriptase (RNaseH-). Second strand cDNA synthesis was subsequently performed using DNA Polymerase I and RNase H. In the reaction buffer, dNTPs with dTTP were replaced by dUTP. Remaining overhangs were converted into blunt ends via exonuclease/polymerase activities.After adenylation of 3 ends of DNA fragments, NEBNext Adaptor with hairpin loop structure were ligated to prepare for hybridization. In order to select cDNA fragments of preferentially 150-200 bp in length, the library fragments were purified with AMPure XP system. Then 3 l USER Enzyme (NEB, USA) was used with size-selected, adaptor-ligated cDNA at 37C for 15 min followed by 5 min at 95C before PCR. PCR was performed with Phusion High-Fidelity DNA polymerase, Universal PCR primer and Index (X) Primer. Finally, the library was purified and then qualified.