Frontiers Journal of Neurology & Neuroscience

Osmoyltes Stabilizing Unusual Configuration Of Hexanucleotide Repeats (G4C2)n

Abstract

The abnormal expansion of hexanucleotide repeats (HRE) GGGGCC (G4C2)n in a non coding region of the C9orf72 gene have been found to lead to cause Amyotrophic lateral sclerosis (ALS) and Frontotemporal dementia (FTD). The transcript of (G4C2)n HRE accumulate as nuclear RNA foci, it sequester and inactivate RNA binding proteins. These HRE can also undergo non ATG initiated translation, as a consequence toxic dipeptide accumulation. HRE can form complex structure like DNA or RNA G-quadruplex and DNA-RNA hybrid, which may cause transcriptional abortion leading to the loss of full length RNA transcripts and accumulation of abortive RNA transcript. In this study, we reported the transition in the configuration of (G4C2)8 from antiparalllel to parallel configuration against heat and in the presence of two different osmolytes (betaine and taurine). The change in the properties and configurations of (G4C2)8 were characterized by circular dichroism (CD) spectroscopy. The parallel configurations were observed in higher concentrations of taurine against heat. Taurine has significant role in stabilizing the structures of (G4C2)8 while there was no such stabilization was observed in the presence of betaine. Our findings are important in order to understand the different folding of HRE (G4C2)n and demonstrate the conformational heterogeneity of the HRE. The presence of different osmolytes affects the unfolding and configurations of G-quadruplex which may be further used to design small molecules targeting neurological disorders. 

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