Molecular interactions required for targeting mRNA to nonsense-mediated decay.

Cells have evolved sophisticated strategies to ensure the accurate expression of genetic information and safeguard against potentially harmful effects of defective messenger RNA (mRNA) and proteins. One such strategy recognizes mRNA translation events that terminate prematurely and targets the faulty mRNA transcript for rapid degradation. This critical quality control activity prevents accumulation of unproductive mRNAs and averts expression of incomplete, potentially toxic proteins. Despite it being a conserved and vital mechanism of gene regulation in most cells, how a cell distinguishes premature translation termination from normal termination and how that leads to accelerated degradation of the faulty mRNA remains poorly understood. This project seeks to identify and investigate key molecular interactions between the translation machinery and mRNA surveillance components necessary to target mRNA for degradation. In addition to advancing understanding of a fundamentally important biological process, this work will provide research experiences for students at the high school, undergraduate and graduate levels. Findings will be disseminated broadly among scientific communities and shared with the public to promote engagement in science. This research will interrogate the molecular interactions and events that occur between the translation and mRNA surveillance machineries to mediate recognition and rapid degradation of nonsense-containing mRNA via nonsense-mediated mRNA decay (NMD). Using the budding yeast model system, innovative genetic and biochemical approaches will be employed to define how UPF1—the central effector of the NMD machinery—impinges on prematurely terminating ribosomes to trigger accelerated decay of the mRNA, and how NMD cofactors, UPF2 and UPF3, contribute to this process. The study aims to uncover previously uncharacterized molecular events that occur downstream of NMD substrate recognition and to advance understanding of this critical RNA quality control mechanism. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.