JUNmRNA Translation Regulation is Mediated by Multiple 5’ UTR and Start Codon Features

Abstract

Regulation of mRNA translation by eukaryotic initiation factors (eIFs) is crucial for cell survival. In humans, eIF3 stimulates translation of theJUNmRNA which encodes the transcription factor JUN, an oncogenic transcription factor involved in cell cycle progression, apoptosis, and cell proliferation. Previous studies revealed that eIF3 activates translation of theJUNmRNA by interacting with a stem loop in the 5′ untranslated region (5′ UTR) and with the 5′ -7-methylguanosine cap structure. In addition to its interaction site with eIF3, theJUN5′ UTR is nearly one kilobase in length, and has a high degree of secondary structure, high GC content, and an upstream start codon (uAUG). This motivated us to explore the complexity ofJUNmRNA translation regulation in human cells. Here we find that JUN translation is regulated in a sequence and structure-dependent manner in regions adjacent to the eIF3-interacting site in theJUN5′ UTR. Furthermore, we identify contributions of an additional initiation factor, eIF4A, inJUNregulation. We show that enhancing the interaction of eIF4A withJUNby using the compound Rocaglamide A (RocA) repressesJUNtranslation. We also find that both the upstream AUG (uAUG) and the main AUG (mAUG) contribute toJUNtranslation and that they are conserved throughout vertebrates. Our results reveal additional layers of regulation forJUNtranslation and show the potential ofJUNas a model transcript for understanding multiple interacting modes of translation regulation.

Decoding RNA Metabolism by RNA-linked CRISPR Screening in Human Cells

“…6G), which was also recapitulated by analysis of previous ribosome profiling studies (Fig S4G). Furthermore, ribosomes initiate at multiple in-frame start codons even in the absence of HHT on mRNAs of several immediate early genes such as JUN, MYC, and JUND [91][92][93] . Together, these observations suggest that collisions occur on these mR-NAs between upstream initiated ribosomes that have transitioned to elongation and HHT-arrested initiating ribosomes at downstream start codons, which are then sensed by GCN1.…”