library_construction_protocol: Total RNA was isolated from the cells with TRIzol Reagent (Invitrogen) and using the PureLink RNA Mini Kit (Invitrogen) following the protocol recommended by the manufacturer. Isolated RNA was treated with DNase (Thermo Fisher) to eliminate the presence of co-precipitated extracellular DNA Messenger RNA was purified from total RNA using poly-T oligo-attached magnetic beads. After fragmentation, the first strand cDNA was synthesized using random hexamer primers, followed by the second strand cDNA synthesis using either dTTP for non strand specific library or dUTP for strand specific library. -- this part was done by Novogene