library_construction_protocol: TRAP was conducted as previously described (Eagle et al., 2020). Polyribosome-associated RNA was affinity purified by homogenizing vHPC tissue in ice-cold tissue-lysis buffer (20mM HEPES [pH 7.4], 150mM KCl, 10mM MgCl2, 0.5mM dithiothreitol, 100 μg/ml cycloheximide, protease inhibitors, and recombinant RNase inhibitors) using a motor-driven Teflon glass homogenizer. Homogenates were centrifuged for 10 min at 2000×g (4 °C), supernatant was supplemented with 1% NP-40 (AG Scientific, #P1505) and 30mM DHPC (Avanti Polar Lipids, #850306P), and centrifuged again for 10 min at 20,000 × g (4 °C). Supernatant was collected and incubated with Streptavidin MyOne T1 Dynabeads (Invitrogen, #65601) that were coated with anti-GFP antibodies (Memorial Sloan-Kettering Monoclonal Antibody Facility; clone names: Htz-GFP-19F7 and Htz-GFP-19C8, 50 μg per antibody per sample) using recombinant biotinylated Protein L (Thermo Fisher Scientific, #29997) for 16–18 h on a rotator (4 °C) in low salt buffer (20mM HEPES [pH 7.4], 350mM KCl, 1% NP-40, 0.5mM dithiothreitol, 100 μg/ml cycloheximide). Beads were isolated and washed with high-salt buffer (20mM HEPES [pH 7.4], 350mM KCl, 1% NP-40, 0.5mM dithiothreitol, 100 μg/ml cycloheximide) and RNA was purified using the RNeasy MicroKit (Qiagen, #74004). In order to increase yield, each RNA sample was initially passed through the Qiagen MinElute™ column three times. Following purification, RNA was quantified using a Qubit fluorometer (Invitrogen) and RNA quality was analyzed using a 4200 Agilent Tapestation (Agilent Technologies). cDNA libraries from 5 ng total RNA were prepared using the SMARTer® Stranded Total RNA-Seq Kit (Takara Bio USA, #635005), according to manufacturer's instructions. cDNA libraries were pooled following Qubit measurement and TapeStation analysis, with a final concentration of 4 nM.