library_construction_protocol: Cells were harvested and RNA was isolated with Trizol. Total RNA was used for generation of mRNA sequencing libraries with the TrueSeq Stranded mRNA kit (Illumina San Diego, USA) according to the manufacturer. The final libraries were stored at -20°C until sequencing. Libraries were sequenced on a HiSeq4000 (Illumina, San Diego, USA) with a paired-end read length of 2 × 100 nucleotides. On average 50 Mio read pairs were generated per sample.