Cells were washed with 1 x PBS (Corning, cat# 21031CV) and lysed with 350 μl RLT Plus buffer (Qiagen) supplemented with 10% 2-mercaptoethanol (Sigma, cat# M6250), vortexed briefly, snap-frozen on dry ice, and stored at -80°C. Subsequently, total RNA was isolated using the RNeasy Plus Micro Kit (Qiagen, cat# 74034). Libraries were prepared with SMARTer Stranded Total RNA-Seq Kit v2 - Pico Input Mammalian (Takara). Indexed libraries were validated for quality and size distribution using a TapeStation 2200 (Agilent). Paired end sequencing (38 bp+38 bp) was performed on a NextSeq 550 or on NovaSeq (61bp+61bp) following the manufacturer's protocol.