library_construction_protocol: Recombinant human Cirbp (His-tagged) protein bound to Ni-NTA magnetic beads (Thermo, USA) was applied to adsorb specifically-bound RNAs. Following several washing with binding buffer, the purified RNAs were eluted by TRIzol extraction, ethanol precipitated and then resuspended in RNase-free water adding DNase for reaction. The RNA fragments were subjected to first strand and second strand cDNA synthesis following by adaptor ligation and enrichment with a low-cycle according to instructions of NEBNext® Ultra RNA LibraryPrep Kit for Illumina (NEB, USA). The final library product was assessed with Agilent 2200 TapeStation andQubit®(Life Technologies, USA) and then sequenced on Illumina （Illumina,USA）platformat with single-end 50bp at Ribobio Co. Ltd (Ribobio, China).