GSM8826160: WT_TT-seq_rep1; Mus musculus; OTHER
4SU enriched RNA was extracted following TT(chem)-seq protocol (Gregersen et al 2020). Briefly, RNA was extracted by TRIzol (Thermo Fisher Scientific, 15596026) accordingly to the manufacturer's instructions. As a control for equal sample preparation, we spiked-in S. cerevisiae (strain BY4741) 4-thiouracil (4TU)-labelled RNA. S. cerevisiae were grown in YPD medium overnight, diluted to an OD600 of 0.1, and grown to mid-log phase (OD600 of 0.8) and labelled with 5 mM 4TU (Sigma-Aldrich, 440736) for 5 min. Total RNA was extracted following a hot-phenol purification (Collin et al 2019.). For purification of 4SU labelled RNA, 100 μg mammalian 4SU labelled RNA was spiked-in 1/100 of 4TU-labelled S. cerevisiae RNA. The 101 μg RNA was fragmented by addition of 20 μL 1 M NaOH to fragment RNA and left on ice for 30 min. Fragmentation was stopped by addition of 80 μL 1 M Tris pH 6.8 and cleaned up twice with Micro Bio-Spin™ P-30 Gel Columns (BioRad, 7326223) according to the manufacturer's instructions. Biotinylation of 4SU-residues were carried out in a total volume of 250 μl, containing 10 mM Tris-HCl [pH 7.4], 1 mM EDTA and 5mg MTSEA biotin-XX linker (Biotium, BT90066) for 30 min at room temperature in the dark. RNA was then purified by phenol:chloroform extraction, denatured by 10 min incubation at 65°C and added to 200 μL μMACS Streptavidin MicroBeads (Miltenyi, 130-074-101). RNA was incubated with beads for 15 min at room temperature and beads applied to a μColumn in the magnetic field of a μMACS magnetic separator. Beads were washed twice with pull-out wash buffer (100 mM Tris-HCl, pH 7.4, 10 mM EDTA, 1 M NaCl and 0.1% Tween20). 4SU-RNA was eluted twice by addition of 100 mM DTT and RNA cleaned up using the RNeasy MinElute kit (Qiagen, 74204). Libraries were prepared using the strand-specific TruSeq total RNA kit (Illumina) using 5 min 65°C fragmentation incubation to anneal primers but to prevent further fragmentation of the samples.