Details
Aaron Engelhart, Ph.D.
Associate Professor
Department of Genetics, Cell Biology, and Development
University of Minnesota
Abstract: Nucleic acids are known to bind and activate cofactors, but many of these bind cofactors without using them productively for catalysis. Heme-binding aptazymes are a counterexample to this trend, and they bind and activate hemin for redox and other (carbene transfer, halide transfer) catalysis. Essentially everything known in this class was either confirmed or thought to be a G-quadruplex (G4) until recently. This changed in 2024, when Liu and coworkers identified Hem1(-2T), a first-in-class non-G-quadruplex heme-binding peroxidase aptazyme, challenging this dogma. Other recent results have demonstrated the biological relevance of these aptamers. For quite awhile, it was unclear if heme aptamers were mostly a laboratory curiosity, or if they had any biological relevance. Cell biology results from the last ten years have demonstrated support for the latter view. Several groups have found – through multiple lines of evidence – G4-hemin interactions could be occurring in live cells.
The discovery of a non-G4 heme aptamer was surprising after repeated selections finding so many G4 aptamers. This led us to investigate whether Hem1(-2T) is rare, or if there are more aptamers like it. We have examined non-G-quadruplex-containing heme-binding aptamers by a range of techniques, including rational design, in vitro selection, and machine learning-based approaches. We have developed single-round selection techniques and machine learning methodologies for processing high-throughput sequencing results from these experiments for rapid identification of aptamers. Using them, we have identified a range of non-G-quadruplex heme aptamers.
Our results suggest the suite of potential heme-binding sequences – in chemistry and biology – is substantially more diverse than previously appreciated.
Bio: Aaron Engelhart’s research group studies new ways to understand and engineer biology. He attended undergrad at Arizona State University (2000-2005), where he worked with Ian Gould studying small molecule-DNA photochemistry. He did his PhD studies at the Georgia Institute of Technology with Nicholas Hud (2005-2011), where he worked on the origins of life and bioorganic chemistry of nucleic acids. He was a NASA Postdoctoral Fellow and Tosteson Postdoctoral Fellow with Jack Szostak at Massachusetts General Hospital/Harvard Medical School (2011-2016), where he studied primitive RNA-based systems and their interaction with liposomal compartments. He started his independent research program at the University of Minnesota in 2016 and is an Associate Professor. His group uses a range of chemical, biological, and ML/AI approaches to engineer biomolecules to develop new behaviors for engineering biology and as tools to study extant living systems.