RNA from exfoliated cervical cells
We extract RNA from tissue using TRIzol reagent according to the protocol. The concentration and purity of RNA were measured with a NanoDrop ND-1000 spectrophotometer. We used Bioanalyzer 2100 and agarose electrophoresis to determine whether the RNA was degraded. The first cDNA strand was synthesized by Invitrogen SuperScript II reverse transcriptase. The second cDNA strand was synthesized from E. coli DNA polymerase I and RNase H. Then, dUTP solution was added for cDNA end repair. After the A-tails addition, magnetic bead screening and purification, the second strand was digested with UDG enzyme and a cDNA library was constructed by PCR. The cDNA library was double-ended PE150 sequenced on the illumina Novaseq 6000 platform.