eIF4A2 promotes 40S ribosome biogenesis in B cells
Eukaryotic initiation factor 4A (eIF4A) plays critical roles during translation initiation of cellular mRNAs by forming the cap-binding eIF4F complex, recruiting the 40S small ribosome subunit, and scanning 5' untranslated region (5' UTR) for the start codon. eIF4A1 and eIF4A2, two isoforms of eIF4A, are highly conserved and exchange freely within the eIF4F complex. The understanding of their biological and molecular function remains incomplete if not fragmentary. In this study, we showed that eIF4A1 and eIF4A2 exhibit different expression patterns during B cell development and activation. Mouse genetic analyses showed that they play critical but different roles during B cell development and humoral immune repnsees. While eIF4A1 controls global protein synthesis, eIF4A2 regulates biogenesis of 18S ribosomal RNA and 40S ribosome subunit. This study demonstrates distinct cellular and molecular functions of eIF4A1 and eIF4A2 and unravels a new role of eIF4A2 in controlling 40S ribosome biogenesis.