“…Recent progress of quantitative RNA labeling techniques enable the absolute measurements of the rates of RNA synthesis and degradation (Rabani et al , 2011; Schwanhäusser et al , 2011; Schwalb et al , 2016; Herzog et al , 2017; Muhar et al , 2018; Schofield et al , 2018). TT‐seq combines a short 4‐thiouridine (4sU) RNA labeling pulse with an RNA fragmentation step to capture newly synthesized RNA, and thereby detects also short‐lived transcripts and allows estimation of the kinetics of RNA metabolism (Schwalb et al , 2016; Michel et al , 2017; Choi et al , 2021; Lidschreiber et al , 2021). To study transcriptional regulation in SL‐2i and SL–mTORi transitions, we measured total RNA and newly synthesized RNA with TT‐seq, annotated transcription units (TUs) de novo , and examined how transcription of different TU classes responds to state transitions.…”