eIF4A3 interactome by IP-MS in mouse ESCs

RNA helicases are involved in multiple steps of RNA metabolism to direct their roles in gene expression, yet their functions in pluripotency control remain largely unexplored. Starting from an RNAi screen of RNA helicases, we identified that eIF4A3, a DEAD-box (Ddx) helicase component of the exon junction complex (EJC), is essential for the maintenance of embryonic stem cells (ESCs). We mapped the eIF4A3 interactomes in mouse ESCs, revealing that eIF4A3 is widely involved in the post-transcriptional regulation of gene expression. Mechanistically, we show that eIF4A3 post-transcriptionally controls the pluripotency-related cell cycle regulators and that its depletion causes cellular differentiation via cell cycle dysregulation. Specifically, eIF4A3 is required for the efficient nuclear export of Ccnb1 mRNA, which encodes Cyclin B1, a key component of the pluripotency-promoting pathway during cell cycle progression of ESCs. Our results reveal a previously unappreciated role of eIF4A3 and its associated EJC in the post-transcriptional cell cycle control in maintaining stem cell pluripotency.