Investigating The Effect Of Various Fmrp Isoforms On Microrna Biogenesis

Fragile X syndrome (FXS) is the most common form of inherited mental impairment and is a result of a trinucleotide repeat expansion in the 5’ untranslated region (UTR) of the fragile X mental retardation-1 (FMR1) gene. The expression of the protein product of this gene, fragile X mental retardation protein (FMRP), is subsequently lost in patients with FXS. FMRP functions as a transporter protein and translational regulator for specific neuronal messenger RNA (mRNA) targets. Recent studies have additionally proposed the involvement of FMRP in the microRNA biogenesis pathway. These short, non-coding microRNAs (miRNAs) associate with the RNA-induced silencing complex (RISC) and bind to target mRNAs, regulating translation and degradation events. Previous studies have demonstrated that FMRP interacts with members of the RISC, such as Argonaute 2 (AGO2) and Dicer, the endonuclease responsible for the final cleavage step in the miRNA biogenesis pathway. In this study, we hypothesize that the FMRP isoforms 1 and 7 (ISO1 and ISO7), as well as their phosphorylated mimics (ISO1-P and ISO7-P), regulate the maturation of miR-125a and miR-125b-2 through interactions with its premature (pre-miRNA) form and the enzyme Dicer. Here, we utilized native polyacrylamide gel electrophoresis (PAGE) in vitro Dicer assays to evaluate the maturation of miR-125a and miR-125b-2 in the presence of various FMRP isoforms.