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 beta 1 (Imp beta 1) and UPF1, a core factor of NMD. Here, we demonstrated that Imp beta 1 knockdown stabilized NMD reporters, and Imp beta 1 and UPF1 interacted and co-regulated an extensive number of target transcripts. Furthermore, Imp beta 1 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 Imp beta 1in nonsense-mediated RNA decay. (C) 2021 Elsevier Inc. All rights reserved.