Structural and Functional Characterization of a Human Ribonuclease Implicated in Obesity

Abstract

Obesity affects a significant number of Americans and greatly increases the risk of developing cardiovascular disease, type‐II diabetes, fatty liver disease, and certain cancers. Understanding how obesity is regulated opens up new avenues of pharmacological interventions to treat obesity, concurrently reducing the risk of co‐morbidities. Mice lacking the broadly expressed enzyme Nocturnin (NOCT) are resistant to diet‐induced obesity and other studies have observed a role for this enzyme in regulating intestinal trafficking of dietary fats and promoting adipogenesis. We have characterized human NOCT and determined that it represses the activity of reporter RNAs in tethered function assays promotes decay of reporter RNAs in vivo. These observations are consistent with a proposed function for NOCT in RNA decay and suggest that there may be a novel pathway that regulates lipid metabolism by targeting mRNAs for degradation. Though the broader physiological effects of gene deletion of NOCT have been described, discovering its molecular function remains an important goal. We have utilized structural and approaches to determine the first crystal structure of the human homolog of NOCT to aid in elucidating its catalytic mechanism. Additionally, we have developed cell‐based assays that will be used to study NOCT function and analyze the effects of active site mutants. These studies describe the structure and activity of human NOCT and provide the foundation for characterizing this enzyme as a potential drug target for obesity and related co‐morbidities.Support or Funding InformationNational Institutes of Health Chemistry‐Biology Interface Training Program (NIH grant 5T32GM008597), American Heart Association Midwestern Affiliate Predoctoral Fellowship, Michigan Nutrition and Obesity Research Center Pilot Grant