UPF3A and UPF3B are paralogous genes in human cells that are involved in the nonsense-mediated decay (NMD) pathway. NMD is a cellular quality control mechanism that monitors mRNAs during translation. Aberrant translation due to features such as the presence of a premature stop codon downstream on an exon-exon junction activates NMD and leads to the degradation of the mRNA. To investigate the role of UPF3B in NMD, we have generated FLAG-TurboID-UPF3B wild type or mutant expressing human Flp-In T-Rex 293 UPF3B knockout cells using the PiggyBac transposon system. We generated proteomic data from the proximity labeled interactome of these UPF3B variants.