As a member of the Protein-Nucleic Acid Interaction (PNAI) Section, Dr. Stagno's research focuses on using structure-based approaches to understand key molecular interactions involving RNA in the regulation of gene expression. By combining various biophysical methods, including NMR, small-angle X-ray scattering (SAXS), and X-ray crystallography, the PNAI is currently investigating the molecular structures and key interactions of two RNA elements that are of great significance to public health. The first is the adenine riboswitch found in the 5'-UTR of mRNAs of many bacterial pathogens. This structured RNA element is essential for regulating gene expression in response to adenine as a metabolite. The second is the Rev response element (RRE), a large (~350 nt) RNA structure located in the env-coding region of the HIV-1 genome. The HIV-1 Rev protein binds to RRE in a highly specific manner, resulting in Rev oligomerization. Formation of this Rev-RRE complex facilitates nuclear export of unspliced and partially spliced mRNAs, which are essential for producing late-stage viral proteins and for providing genomes for budding virions. Because RRE is a unique feature of HIV-1 mRNA and is essential to the virus life-cycle, this RNA element may serve as an important molecular target for HIV-therapeutic design. In 2013, the PNAI determined the three-dimensional topological structure of RRE using SAXS.

Although this structure was a major breakthrough in furthering our understanding of the Rev-RRE interaction, atomic resolution is needed to design molecules that specifically target the Rev binding sites on RRE. Toward this goal, Dr. Stagno is using X-ray crystallography to elucidate the structures of RRE-containing complexes.