Fig. 7: AAG and AAGGAG form different secondary structures at the DNA and RNA level.
From: Identification and characterisation of pathogenic and non-pathogenic FGF14 repeat expansions
A Schematic representation of the region on chromosome 13q33.1 containing the FGF14 gene showing isoforms 1 (ENST00000376143.5; NM_004115.4) and 2 (ENST00000376131.9; NM_175929.3), which have alternative first exons. The gene is on the reverse strand. The green arrows show the location of the AAG expansion in intron 1 of isoform 2. The location of the previously unreported nonsense variant (NM_175929.3: c.239 T > G; p.Leu80*) reported in this study is indicated in purple. B Schematic representation of FGF14 pre-mRNA isoforms 1 and 2. The expansion (green arrow) is composed of CUU repeats in RNA context. C Secondary structures formed by AAG and AAGGAG repeats at the DNA and RNA level, assessed by circular dichroism spectroscopy. AAG repeats form an antiparallel homoduplex whereas AAGGAG repeats form a parallel homoduplex at the DNA level. At the RNA level, the AAGGAG repeats fold into a parallel guanine-quadruplex (G4) while AAG repeats adopt an A-form RNA structure. On the contrary, the CTT and TCTCCT repeats adopt a B-form and CUU and UCUCCU repeats did not form any particular secondary structure under the tested conditions. G-quadruplex and other DNA/RNA structures were created with BioRender.com released under a Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International license.
