Defense Date

6-20-2017

Graduation Date

Summer 1-1-2017

Availability

One-year Embargo

Submission Type

dissertation

Degree Name

PhD

Department

Chemistry and Biochemistry

Committee Chair

Mihaela Rita Mihailescu

Committee Member

Michael Cascio

Committee Member

Ellen Gawalt

Committee Member

Daryl Bosco

Keywords

ALS/FTD, Hepatitis C Virus, Fragile X Syndrom, Protein, Nucleic Acid, Biophysical Characterization, Neurodegeneration

Abstract

This study investigates protein nucleic acid interactions between various proteins and G quadruplex (GQ) forming messenger RNAs (mRNAs) in human neurological disorders. GQ structures are formed in DNA/RNA, when four guanine residues form planar tetrads stabilized by Hoogsteen base pairing, that stack forming a GQ structure stabilized by potassium ions. These GQ structures are targeted by the arginine-glycine-glycine (RGG) repeat domain containing RNA-binding domain.

Three RGG domain containing RNA-binding proteins, all of which have been implicated in neurological disorders, and their interactions with GQ forming mRNAs, were investigated in this study: fused in sarcoma (FUS), fragile X mental retardation protein (FMRP), and hnRNP Q1. Initially we analyzed the interactions between FUS and two neuronal GQ forming mRNAs, Shank1 and PSD-95 mRNAs. Our results indicate that FUS binds these GQ structures with high affinity and specificity. This is the first study showing that FUS recognizes the GQ RNA structure in neuronal mRNA targets, suggesting a role for localization of the mRNA to the synapse. FMRP, whose loss of expression leads to the fragile X syndrome, is a translation regulator that has been shown to bind to GQ mRNA structures. Here we identified another FMRP GQ forming mRNA target, SMNDC1 mRNA, and characterized its interactions with FMRP. FUS has also been implicated in amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) and more recently it has been shown that an expansion of (G4C2) repeats within the C9ORF72 is causative of ALS/FTD. We and others have shown that these repeats form GQ structures and here we demonstrate that both FMRP and FUS bind these repeats, suggesting a possible mechanism by which the repeat expansion leads to the sequestration of RNA binding proteins. Finally, we demonstrate that hnRNP Q1, a protein involved in mRNA processing, recognizes a GQ structure in GAP43 mRNA. This study increases our understanding of the biological functions of the mRNA GQ structure and of their role in neurodegenerative diseases.

Language

English

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