Lin28b

For cloning of the SunTag-FL2 construct, we used the SINAPs plasmid from the Singer lab (Addgene #84561)⁴⁴ and a tdTomato-FL2 (containing the 3’UTR of FL2) plasmid previously cloned in-house using the tdTomato-C1 vector (Addgene #54653), a human FL2 clone in pANT7_cGST (DNASU, Arizona State University, Tempe, AZ, clone: HsCD00403041) and a human FL2 3’UTR construct (Switchgear Genomics #S811553). The Ubc promoter, flag tag and SunTag reporter were cloned from the SINAPs construct to replace the CMV promoter and tdTomato reporter of the tdTomato-FL2 plasmid using NEBuilder HiFi DNA Assembly technology (NEB).
The plasmids used for IMP RBP overexpression, GFP-ZBP1^{33 (link)}, GFP-IGF2BP2 and GFP-IGF2BP2 KH3 mutant^{39 (link)}, were from the Singer laboratory. The Lin28 plasmids were purchased from Addgene; Lin28A (#51371), Lin28B (#51373) and Lin28A-mCCHC (#51372). The miRNA let-7 inhibitor sequence (3’-CUCCAUCAUCCAACAU-5’) was previously validated for broad let-7 family inhibition (Frost & Olson, 2011). The custom miRCURY LNA miRNA inhibitor was purchased from Qiagen (Cat num 339146).

MiR‐26a‐5p mimics, miR‐29a‐3p mimics, and negative control oligonucleotides (miR‐CON) were purchased from Sigma (#HMI0415, #HMC0434, #HMC0002, respectively). Small interfering pool RNA of LIN28B, RAN, and control RNA (siLIN28B, siRAN, siCon; five siRNAs per pool) were purchased from Santa Cruz Biotechnology (#SC‐105614, #SC‐36382, #SC‐37007, respectively). LIN28B and AURKA plasmids were purchased from Addgene (#51375 and #20427, respectively). Luciferase reporter gene plasmids, including wild‐type AURKA 3′‐UTR, wild‐type LIN28B 3′‐UTR, and their seed mutants, were synthesized and subcloned into pmirGLO vectors, which were confirmed by sequencing.