GSE184247
eIF4A1 enhances LARP1-mediated translational repression during mTORC1 inhibition
Eukaryotic translation initiation factor (eIF) 4A — a DEAD-box RNA-binding protein — plays an essential role in translation initiation. Recent reports have suggested helicase-dependent and helicase-independent functions for eIF4A, but the multifaceted roles of eIF4A have not been fully explored. Here, we show that eIF4A1 enhances translational repression during the inhibition of mechanistic target of rapamycin complex 1 (mTORC1), an essential kinase complex controlling cell proliferation. RNA pulldown followed by sequencing revealed that eIF4A1 preferentially binds to mRNAs containing terminal oligopyrimidine (TOP) motifs (TOP mRNAs), whose translation is rapidly repressed upon mTORC1 inhibition. This selective interaction depends on a La-related RNA-binding protein, LARP1. Ribosome profiling revealed that deletion of EIF4A1 attenuated the translational repression of TOP mRNAs upon mTORC1 inactivation. Moreover, eIF4A1 increases the affinity between TOP mRNAs and LARP1 and thus ensures stronger translational repression upon mTORC1 inhibition. Our data show the multimodality of eIF4A1 in modulating protein synthesis through an inhibitory binding partner and provide a unique example of the repressive role of a universal translational activator. Overall design: Ribosome profiling of EIF4A1 KO and EIF4A2 KO cells with PP242 treatment, RNA-Seq of EIF4A1 KO cells, RNA pulldown-seq of SBP-EIF4A1- and SBP-EIF4A2- expressing cells, and RIP-seq of SBP-EIF4A1-expressing cells upon LARP1 knockdown.