library_construction_protocol: Cells were lysed in 400 μL TRI reagent (Invitrogen, AM9738). Chloroform (120 μL) was added, and samples were mixed vigorously followed by centrifugation at 21,000 × g for 15 min at 4°C. The upper aqueous phase was transferred to a new tube, extracted again with an equal volume of chloroform, and centrifuged at 21,000 × g for 1 min at 4°C. For RACE, the RNA was precipitated by supplementing the aqueous phase with 300 mM NaCl and 30 μg GlycoBlue (AM9516), followed by addition of an equal volume of isopropanol and incubation at −20°C overnight. For CAGE, the RNA was precipitated with LiCl (2.5 M final) at −20°C overnight. RNA was pelleted by centrifugation at 21,000 × g for 30 min at 4°C, washed once with 70% ethanol, and resuspended in RNase-free water. RNA concentration was determined using a Nanodrop. Library preparation was outsourced to DNAFORM for their standard CAGE-Seq pipeline.