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Riboswitches are RNA structures that regulate gene expression by binding directly to a small-molecule ligand. They are often found in the 3' or 5' untranslated region (UTR) of an mRNA strand. Riboswitches are abundant bacteria, but only one has been found in fungi and plants in Eukaria. No riboswitch to date has been found in humans. Jeff Morgan, Ph.D. at the Rutter lab, asked if humans could also have riboswitches. Utilizing dimethyl sulfate (DMS) structure probing and mass spectrometry integrated with equilibrium dialysis (MIDAS), Jeff screened the 5' UTR of HEK293 mRNA and found evidence of specific metabolite-RNA interactions. (Figure 1). One of the hits from Dr. Morgan's preliminary data was the 5' UTR of Cytochrome C Oxidase Subunit 7B (COX7B) binding to cAMP. COX7B is a subunit protein of Complex IV in the mitochondria's electron transport chain (ETC). To date, little is known about the protein and its functions of the ETC. The research of this project aimed to answer two questions: First, does COX7B protein expression change when cAMP levels are high? Second, can we provide evidence for COX7B binding to cAMP? Using an in-vitro translation assay, an in-vivo luciferase reporter assay, western blotting, and microscale thermophoresis (MST), we find that the 5' UTR of COX7B is responsive to cAMP levels, suggesting this may be among the first human riboswitches discovered. One hypothesis for COX7B function is that it may stabilize supercomplexes of proteins within the ETC to allow the cell to adapt to environmental conditions. For future directions, we plan to test this hypothesis by using blue native PAGE to determine supercomplex formation. Although we do not know if COX7B has a function other than a structural component of complex IV, the possibility of COX7B mRNA being a riboswitch may suggest its protein function is more than just a structural one.