(337ao) 8-Oxo-7,8-Dihydroguanosine Alters RNA Enzymatic Degradation Behavior of Polynucleotide Phosphorylase

Research Interests include Protein-RNA Interactions, Protein Biophysics, Protein Engineering, Molecular Dynamics Simulations, and Structure-Function Relationships

The impacts of oxidative stress are pervasive across all biomolecules within the cell. Oxidants such as hydrogen peroxide, paraquat, and air pollutants can lead to the generation of reactive oxygen species (ROS) that have been shown to oxidize DNA, proteins, lipids, and RNA. The most common oxidized base found in RNA is 8-oxo-7,8-dihydroguanosine (8-oxoG), an RNA modification that has been linked to both mistranslation and drops in translational activity. Among the few proteins identified that show a binding preference for this RNA modification is polynucleotide phosphorylase (PNPase), an exoribonuclease that represents a constituent of the RNA degradosome. This protein has been shown to be important in cell survival under oxidative stress, but the molecular mechanisms by which this protein recognizes and actions upon 8-oxoG present in RNA transcripts remains unclear. Here, we demonstrate that PNPase exhibits interesting enzymatic behavior upon encountering 8-oxoG through functional biochemical experiments. We further investigate the potential regions responsible for this enzyme’s functional behavior and demonstrate that the PNPase catalytic core, rather than the RNA binding domains, are implicated. Finally, we perform additional mutational analysis of regions within the catalytic core based on structural insights to validate the importance of these regions for the activity of the protein in the context of 8-oxoG containing RNA.