Isothermal Calorimetric Measurements of Metal Ion Interaction with TAR RNA

Abstract

The trans‐activation response (TAR) element of HIV‐1 is essential for transcriptional elongation in HIV‐1. It consists of a stem‐loop containing a trinucleotide bulge (UCU) and is capped by a hexaloop sequence located in the 5′ UTR in HIV‐1. The trinucleotide bulge interacts with the arginine‐rich basic domain of the Tat protein to increase the rate of transcription by nearly 100‐fold. Thermodynamic studies in our laboratory have previously examined the effects of TAR RNA interactions with divalent metal ions to show that single nucleotide modifications can lead to differences in RNA‐ion interactions. Thermal denaturation studies show an increase in wild type construct stability in 10 mM Ca2+ or Mg2+ as compared to 1 M KCl. In this study, the thermodynamics of metal ion binding to the TAR RNA sequence is investigated by directly measuring the heat released using isothermal titration calorimetry (ITC). TAR RNA derived constructs were titrated with magnesium, calcium, and arginine containing buffers to measure the enthalpic contributions and the binding affinity of the ions to further understand different types of RNA‐metal ion interactions.Support or Funding InformationDepartment of Chemistry and BiochemistryColorado CollegeThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.