Importin β1 mediates nuclear import of the factors associated with nonsense-mediated RNA decay

In eukaryotic cells, nonsense-mediated RNA decay (NMD) is an essential physiological mechanism coupled to translation, regulating the stability of abnormal RNA containing premature termination codon (PTC) and a significant fraction of normal transcriptomes. So far, the molecular regulation mechanism of NMD pathway is far from fully elucidated. Previously, we observed the interaction between importin β1 (Impβ1) and UPF1, a core factor of NMD. Here, we demonstrated that Impβ1 knockdown stabilized NMD reporters, and Impβ1 and UPF1 interacted and co-regulated an extensive number of target transcripts. Furthermore, Impβ1 affected the interaction between UPF1 and SMG5 or MAGOH, and the nuclear distributions of UPF1, SMG1, SMG5 and MAGOH. Besides, Ran knockdown extremely promoted the dissociation of UPF1 from SMG5 or MAGOH. Our findings provide molecular insight into the potential function of Impβ1in nonsense-mediated RNA decay.