Abstract
G-quadruplexes are widespread four-stranded structures that are adopted by G-rich regions of both DNA and RNA and are involved in essential biological processes such as mRNA translation. They are formed by the stacking of two or more G-quartets that are linked together by three loops. Although the maximal loop length is usually fixed to 7 nt in most G-quadruplex-predicting software, it has already been demonstrated that artificial DNA G-quadruplexes containing two distal loops that are limited to 1 nt each and a central loop up to 30 nt long are likely to form in vitro. This report demonstrates that such structures possessing a long central loop are actually found in the 5'-UTRs of human mRNAs. Firstly, 1453 potential G-quadruplex-forming sequences (PG4s) were identified through a bioinformatic survey that searched for sequences respecting the requirement for two 1-nt long distal loops and a long central loop of 2-90 nt in length. Secondly, in vitro in-line probing experiments confirmed and characterized the folding of eight candidates possessing central loops of 10-70 nt long. Finally, the biological effect of several G-quadruplexes with a long central loop on mRNA expression was studied in cellulo using a luciferase gene reporter assay. Clearly, the actual definition of G-quadruplex-forming sequences is too conservative and must be expanded to include the long central loop. This greatly expands the number of expected PG4s in the transcriptome. Consideration of these new candidates might aid in elucidating the potentially important biological implications of the G-quadruplex structure.
Highlights
Guanine-rich nucleic acid sequences can fold into a wellknown tetrahelical structure called G-quadruplex
Several studies focused on the bioinformatic analysis of G-quadruplexes in the human genome confirmed the presence of a significant number of potential G-quadruplex-forming sequences (PG4s) in various biologically relevant regulatory regions such as the promoter elements of genes, telomeres, and the UTRs of mRNAs (Huppert and Balasubramanian 2005; Eddy and Maizels 2006; Huppert et al 2008; Beaudoin and Perreault 2010, 2013)
Representative, natural 5′-UTR PG4 sequences with variable central loop lengths were chosen from the database (Table 1) and subjected to in-line probing experiments to verify their ability to fold into G-quadruplex structures in vitro
Summary
Guanine-rich nucleic acid sequences can fold into a wellknown tetrahelical structure called G-quadruplex. The stability of the structure is affected by several features, including the number of G-quartets, the possibility of bulge formation, the type and concentration of monovalent cations in solution, the sequence of the nucleic acid molecule itself, and the length of the loops composing the G-quadruplex Several studies focused on the bioinformatic analysis of G-quadruplexes in the human genome confirmed the presence of a significant number of potential G-quadruplex-forming sequences (PG4s) in various biologically relevant regulatory regions such as the promoter elements of genes, telomeres, and the UTRs of mRNAs (Huppert and Balasubramanian 2005; Eddy and Maizels 2006; Huppert et al 2008; Beaudoin and Perreault 2010, 2013). Considerable effort has been spent trying to understand the principles
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
