miRNA biogenesis

My thesis work at University of California Los Angeles (UCLA) in the lab of Dr. Feng Guo, focused the function of Fe3+ heme in microRNA (miRNA) biogenesis. I characterized a previously undiscovered RNA-binding heme domain (Rhed) in the protein DGCR8. My colleague Dr. Grant Shoffner discovered Rhed domain defines the stoichiometry for the Microprocessor complex responsible for the maturation of miRNA in the nucleus.  Without the Rhed domain the binding affinity for primary microRNA substrates is greatly reduced in all the pri-miRNAs we tested. You can find more details in Cell Reports, Quick-Cleveland et al. 2014.

Through biochemical characterization of the Rhed domain, I also discovered many mutations that resulted in reduced affinity for heme. The mutation of three acidic amino acids in the Rhed completely abolish the ability of DGCR8 to bind heme. This mutation is completely inactive for miRNA processing both in vitro and in several human cell lines. In collaboration with my colleague Sara Weitz, we discovered that by manipulating the cellular pool of available heme in human cells we could regulated miRNA processing activity. We have a manuscript on bioRxiv: Fe(III) heme sets an activation threshold for processing distinct  groups of pri-miRNAs in mammalian cells.