UPF1 is an essential RNA helicase that detects mRNAs containing premature stop codons and triggers their degradation. This domain contains 3 zinc binding motifs and forms interactions with another protein (UPF2) that is also involved nonsense-mediated mRNA decay (NMD) [1].

1: Crystal structure of the UPF2-interacting domain of nonsense-mediated mRNA decay factor UPF1. Kadlec J, Guilligay D, Ravelli RB, Cusack S; RNA. 2006;12:1817-1824. PMID:16931876