A G‐Rich element forms a G‐quadruplex and regulates BACE1 mRNA alternative splicing

Abstract

β-site APP cleaving enzyme 1 (BACE1) is the transmembrane aspartyl protease that catalyzes the first cleavage step in the proteolysis of the amyloid β-protein precursor (APP) to the amyloid β-protein (Aβ), a process involved in the pathogenesis of Alzheimer disease. BACE1 pre-mRNA undergoes complex alternative splicing, the regulation of which is not well understood. We identified a G-rich sequence within exon 3 of BACE1 involved in controlling splice site selection. Mutation of the G-rich sequence decreased use of the normal 5′ splice site of exon 3, which leads to full-length and proteolytically active BACE1, and increased use of an alternative splice site, which leads to a shorter, essentially inactive isoform. Nuclease protection assays, nuclear magnetic resonance, and circular dichroism spectroscopy revealed that this sequence folds into a G-quadruplex structure. Several proteins were identified as capable of binding to the G-rich sequence, and one of these, heterogeneous nuclear ribonucleoprotein H (hnRNP H), was found to regulate BACE1 exon 3 alternative splicing and in a manner dependent on the G-rich sequence. Knockdown of hnRNP H led to a decrease in the full-length BACE1 mRNA isoform as well as a decrease in Aβ production from APP, suggesting new possibilities for therapeutic approaches to AD.

The Disease-associated r(GGGGCC) Repeat from the C9orf72 Gene Forms Tract Length-dependent Uni- and Multimolecular RNA G-quadruplex Structures

“…Although preliminary, these results suggest that the expanded (GGGGCC) n repeat may potentially autoregulate C9orf72 splicing (4). Our observation that the r(GGGGCC) n repeat can assume a G-quadruplex opens the question as to whether such structures may affect C9orf72 splicing outcomes, as occurs for other genes (33,42). We found that the splicing regulator ASF/ SF2 bound in vitro to the C9orf72 repeat, as predicted based on sequence specificity (34).…”

“…Gquadruplexes can affect alternative splicing (33,42). The (GGGGCC) n repeat lies within the noncoding region of the C9orf72 gene, which can be alternatively spliced to three isoforms (3,4).…”

“…G-quadruplexes in RNA have been associated with regulating alternative splicing by serving as an exonic splice enhancer (32,33). DeJesus-Hernandez et al (4) reported three variant splice isoforms of the C9orf72 transcript where the (GGGGCC) n repeat is situated in the promoter (v1) or the first intron between two noncoding exons (v2,3).…”

The RNA Stem–Loop to G-Quadruplex Equilibrium Controls Mature MicroRNA Production inside the Cell

“…2,3 Formation and stability of these RNA structures is dependent on the presence of different ions under in vitro conditions. 4-8 Functionally, RNA G-quadruplexes act as modulators of gene expression and have been shown to regulate a number of processes such as mRNA translation, 9-12 telomere biology, 13 mRNA localisation, 14 pre-mRNA splicing 15 to name a few. Absence of complementary strand for RNA makes it more amenable to form secondary structures in comparison to duplex DNA.…”

Structure and target interaction of a G-quadruplex RNA-aptamer

“…[3][4][5] Furthermore, GQs hold regulative potential for gene expression either on the transcriptional level by being part of or close to promoters in genomic DNA (e.g. c-MYC or bcl2 promoter) 6,7 or as regulators of splicing 8 and translation 9 (inhibitory or enhancing) when present in mRNAs and finally as regulative elements by binding of certain effector proteins. 3,10 It has been shown that due to this fact GQs are also crucial elements in the development or progression of malignancy such as neurodegenerative disorders 11 and cancer.…”