A cooperative mechanism of target RNA selection via germ-cell-specific RNA-binding proteins NANOS2 and DND1

The germ-cell-specific RNA-binding protein (RBP) NANOS2 plays a pivotal role in male gonocyte differentiation and spermatogonial stem cell maintenance. Although NANOS2 interacts with the CNOT deadenylation complex and Dead end 1 (DND1) to repress target RNAs, the molecular mechanisms underlying target mRNA selection remain unclear because of the limited cell resource in vivo. Here, we demonstrate that exogenous NANOS2-DND1 suppresses target mRNAs in somatic cells. Using this somatic cell system, we find that NANOS2 interacts with RNA-bound DND1 and recruits the CNOT complex to the mRNAs. However, a fusion construct composed of the CNOT1-binding site of NANOS2 (NIM) and DND1 fails to repress the target gene expression. Therefore, NANOS2 is required not only for recruitment of the CNOT complex but also for selecting the target mRNA with DND1. This study reveals that NANOS2 functions as a second-layer RBP for the target recognition and functional adaptation of DND1.