title: Amyloid Precursor Protein Translation Is Regulated by a 3'UTR Guanine Quadruplex.
abstract: A central event in Alzheimer's disease is the accumulation of amyloid β (Aβ) peptides generated by the proteolytic cleavage of the amyloid precursor protein (APP). APP overexpression leads to increased Aβ generation and Alzheimer's disease in humans and altered neuronal migration and increased long term depression in mice. Conversely, reduction of APP expression results in decreased Aβ levels in mice as well as impaired learning and memory and decreased numbers of dendritic spines. Together these findings indicate that therapeutic interventions that aim to restore APP and Aβ levels must do so within an ideal range. To better understand the effects of modulating APP levels, we explored the mechanisms regulating APP expression focusing on post-transcriptional regulation. Such regulation can be mediated by RNA regulatory elements such as guanine quadruplexes (G-quadruplexes), non-canonical structured RNA motifs that affect RNA stability and translation. Via a bioinformatics approach, we identified a candidate G-quadruplex within the APP mRNA in its 3'UTR (untranslated region) at residues 3008-3027 (NM_201414.2). This sequence exhibited characteristics of a parallel G-quadruplex structure as revealed by circular dichroism spectrophotometry. Further, as with other G-quadruplexes, the formation of this structure was dependent on the presence of potassium ions. This G-quadruplex has no apparent role in regulating transcription or mRNA stability as wild type and mutant constructs exhibited equivalent mRNA levels as determined by real time PCR. Instead, we demonstrate that this G-quadruplex negatively regulates APP protein expression using dual luciferase reporter and Western blot analysis. Taken together, our studies reveal post-transcriptional regulation by a 3'UTR G-quadruplex as a novel mechanism regulating APP expression.
authors.affiliation: Department of Biology, Drexel University, Philadelphia, PA, United States of America.
authors.forename: Ezekiel
authors.initials: E
authors.lastname: Crenshaw
authors.affiliation: Department of Biology, Drexel University, Philadelphia, PA, United States of America.|Department of Chemistry, Drexel University, Philadelphia, PA, United States of America.
authors.forename: Brian P
authors.initials: BP
authors.lastname: Leung
authors.affiliation: Department of Chemistry, Pennsylvania State University, University Park, PA, United States of America.|Department of Biochemistry & Molecular Biology, Center for RNA Molecular Biology, Pennsylvania State University, University Park, PA, United States of America.|Department of Chemistry, University of Cambridge, Cambridge, United Kingdom.
authors.forename: Chun Kit
authors.initials: CK
authors.lastname: Kwok
authors.affiliation: Department of Biology, Drexel University, Philadelphia, PA, United States of America.
authors.forename: Michal
authors.initials: M
authors.lastname: Sharoni
authors.affiliation: Department of Chemistry, Pennsylvania State University, University Park, PA, United States of America.
authors.forename: Kalee
authors.initials: K
authors.lastname: Olson
authors.affiliation: Department of Biology, Drexel University, Philadelphia, PA, United States of America.
authors.forename: Neeraj P
authors.initials: NP
authors.lastname: Sebastian
authors.affiliation: Department of Biology, Drexel University, Philadelphia, PA, United States of America.
authors.forename: Sara
authors.initials: S
authors.lastname: Ansaloni
authors.affiliation: Department of Chemistry, Drexel University, Philadelphia, PA, United States of America.
authors.forename: Reinhard
authors.initials: R
authors.lastname: Schweitzer-Stenner
authors.affiliation: Department of Biology, Drexel University, Philadelphia, PA, United States of America.|Department of Neurobiology & Anatomy, Drexel University College of Medicine, Philadelphia, PA, United States of America.
authors.forename: Michael R
authors.initials: MR
authors.lastname: Akins
authors.affiliation: Department of Chemistry, Pennsylvania State University, University Park, PA, United States of America.|Department of Biochemistry & Molecular Biology, Center for RNA Molecular Biology, Pennsylvania State University, University Park, PA, United States of America.
authors.forename: Philip C
authors.initials: PC
authors.lastname: Bevilacqua
authors.affiliation: Department of Biology, Drexel University, Philadelphia, PA, United States of America.|Department of Biochemistry & Molecular Biology, Drexel University College of Medicine, Philadelphia, PA, United States of America.|Department of Neurobiology & Anatomy, Drexel University College of Medicine, Philadelphia, PA, United States of America.
authors.forename: Aleister J
authors.initials: AJ
authors.lastname: Saunders
mesh_terms: D020413:3' Untranslated Regions; D016564:Amyloid beta-Protein Precursor / Q000235:genetics* / Q000378:metabolism; D054856:G-Quadruplexes; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism
chemical_list: D020413:3' Untranslated Regions; D016564:Amyloid beta-Protein Precursor; D012333:RNA, Messenger