Rita Mihaela Mihailescu, Ph.D.Professor
Bayer School of Natural and Environmental Sciences
Chemistry & Biochemistry
Education:B.S., M.S. University of Bucharest
Ph.D., Wesleyan University, CT
Post Doctoral Fellow, Center for Advanced Research in Biotechnology
Protein-Nucleic Acid Interactions
Our research interests are in the field of protein-nucleic acid interactions, in particular protein-RNA interactions. We use molecular biology and biochemistry techniques to produce and purify the proteins and RNAs of interest and biophysical techniques that include NMR spectroscopy, fluorescence spectroscopy and UV-Vis spectroscopy, to analyze the interactions between these molecules.
Biophysical characterization of the Fragile X Mental Retardation Protein interactions with G-quartet forming RNA target(s)
Fragile X mental retardation syndrome is the most common form of inherited mental retardation, affecting approximately 1 in 4000 males and approximately 1 in 8000 females. The syndrome is caused by the loss of a normal cellular protein, named the fragile X mental retardation protein (FMRP). Despite extensive research in the last decade, it still not fully understood what relationship there is between the absence of FMRP and the phenotype of the fragile X syndrome. FMRP has RNA binding activity and the current model for its function is that it is involved in the transport and translation regulation of specific messenger RNA targets. Although these specific mRNA targets of FMRP remain elusive, recent biochemical studies have determined that FMRP binds with high affinity, using its arginine-glycine-glycine (RGG box) domain, to RNA sequences rich in guanine content, that have the potential to fold into G quartets.
G quartet structures consist of guanine tetrads held together by reverse Hoogsteen base pairs (see figure). Several G quartet planar structures can stack and the formation of such complexes is dependent on the presence of monovalent cations that may lie within the plane of each quartet or between planes. K+ or Na+ cations stabilize these structures, whereas their formation the presence of Li+.
Since the RNA binding activity of FMRP is relevant for its function, we are interested in investigating the molecular basis of RNA recognition by FMRP: does FMRP recognize the G-quartet containing RNA via a sequence specific or via a structure specific mechanism or both? Secondly, if FMRP binds its RNA target(s) via the G quartet motifs, what is its function, to stabilize or destabilize these structures; is this function dependent on the sequence context in which the G quartet is located?
To address these questions we are studying the interactions of FMRP with several G-quartet forming potential RNA targets that include Semaphorin 3F mRNA and MAP1B mRNA.