The nonsense-mediated mRNA decay (NMD) pathway monitors premature translation termination and degrades aberrant mRNAs. In yeast, it has been proposed that a surveillance complex searches 3' of a nonsense codon for a downstream sequence element (DSE) associated with RNA-binding proteins. An interaction between the complex and the DSE-binding protein(s) triggers NMD. Here we describe the identification and characterization of the Hrp1/Nab4 protein as a DSE-binding factor that activates NMD. Mutations in HRP1 stabilize nonsense-containing transcripts without affecting the decay of wild-type mRNAs. Hrp1p binds specifically to a DSE-containing RNA and interacts with Upf1p, a component of the surveillance complex. A mutation in HRP1 that stabilizes nonsense-containing mRNAs abolishes its affinity for the DSE and fails to interact with Upf1p. We present a model describing how Hrp1p marks a transcript for rapid decay.
SciCrunch is a data sharing and display platform. Anyone can create a custom portal where they can select searchable subsets of hundreds of data sources, brand their web pages and create their community. SciCrunch will push data updates automatically to all portals on a weekly basis. User communities can also add their own data to scicrunch, however this is not currently a free service.