RNA was isolated with the use of TRI Reagent according to the manufacturer's instructions. Northern blot was performed according to standard protocol described elsewhere (25 (link)). Shortly, 1 μg of RNA was run on an agarose gel followed by overnight capillary transfer to Hybond-N membrane (GE Healthcare). DecaLabel DNA Labeling Kit (Thermo Fisher Scientific) was used to radioactively label probes with [α-32P] dATP (Hartmann Analytic). In case of strand-specific hybridizations (Figure 5), in vitro transcription was performed utilizing polymerase chain reaction (PCR) products containing S6 or T7 promoter sequence (one on each end) as a template. Primers used to generate PCR products applied as templates for obtaining radiolabeled probes are listed in Supplementary Table S3. Results were recorded after overnight exposure to PhosphorImager screens (FujiFilm) using Typhoon FLA 9000 scanner (GE Healthcare). Quantification was performed using Multi Gauge V3.0 software (Fujifilm).