The cationic porphyrin TMPyP4 destabilizes the tetraplex form of the fragile X syndrome expanded sequence d(CGG)n

Pnina Weisman-Shomer, Esther Cohen, Inbal Hershco, Samer Khateb, Orit Wolfovitz-Barchad, Laurence H. Hurley, Michael Fry

Research output: Contribution to journalArticle

47 Scopus citations

Abstract

Fragile X syndrome, the most common cause of inherited mental retardation, is instigated by dynamic expansion of a d(CGG) trinucleotide repeat in the 5′-untranslated region of the first exon of the FMR1 gene, resulting in its silencing. The expanded d(CGG)n tract readily folds into hairpin and tetraplex structures which may contribute to the blocking of FMR1 transcription. In this work, we report that the cationic porphyrin 5,10,15,20-tetra(N-methyl-4-pyridyl)porphin (TMPyP4) effectively destabilizes in vitro the G′2 bimolecular tetraplex structure of d(CGG)n while it stabilizes the G′2 tetraplex: form of the telomeric sequence d(TTAGGG)2. Similarly to TMPyP4, the hnRNP-related protein CBF-A also destabilizes G′2 tetrahelical d(CGG)n while binding and stabilizing tetraplex telomeric DNA. We report that relative to each agent individually, successive incubation of G′2 d(CGG)n with TMPyP4 followed by exposure to CBF-A results in a nearly additive extent of disruption of this tetraplex form of the repeat sequence. Our observations open up the prospect of unfolding secondary structures of the expanded FMR1 d(CGG)n tract of fragile X cells by their exposure to low molecular size drugs or to proteins such as TMPyP4 or CBF-A.

Original languageEnglish (US)
Pages (from-to)3963-3970
Number of pages8
JournalNucleic acids research
Volume31
Issue number14
DOIs
StatePublished - Jul 15 2003

ASJC Scopus subject areas

  • Genetics

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