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  • Title: Electrospray ionization mass spectrometric exploration of the high-affinity binding of three natural alkaloids with the mRNA G-quadruplex in the BCL2 5'-untranslated region.
    Author: Tan W, Yuan G.
    Journal: Rapid Commun Mass Spectrom; 2013 Feb 28; 27(4):560-4. PubMed ID: 23322663.
    Abstract:
    RATIONALE: The BCL2 gene encodes an integral outer mitochondrial membrane protein (25 kDa) which regulates the apoptotic death of cells. There is a 25-nucleotide G-rich sequence in the 5'-untranslated region (5'-UTR) of the BCL2 mRNA, which can adopt a G-quadruplex structure. Small molecules which could tightly bind to this structure have a potential function in the regulation of the expression of the BCL2 mRNA. METHODS: The 25-mer oligonucleotide (5'-G(5)CCGUG(4)UG(3)AGCUG(4)-3') was synthesized by TaKaRa Biotechnology Co., Ltd. (TaKaRa, Dalian) with high-performance liquid chromatography (HPLC) purification. Electrospray ionization (ESI) mass spectrometry (MS) was used to probe the binding properties of natural small molecules (P) with the mRNA G-quadruplex in the BCL2 5'-UTR (BCL2Q). Collision-induced dissociation (CID) mass spectrometry and circular dichroism (CD) spectroscopy were performed to evaluate the stabilization of the mRNA G-quadruplex and its complexes. RESULTS: The results from ESI mass spectra showed that three natural alkaloids (nitidine, palmatine, and jatrorrizine) have high binding affinities to the mRNA G-quadruplex with the binding stoichiometry ranging from 1:1 to 3:1. CID mass spectrometry results revealed that the G-quadruplex-ligand complex lost bases first rather than losing the binding molecules. Increases in the T(m) values of the complexes of the G-quadruplex with the natural alkaloids in the CD melting experiments demonstrated that the three small molecules can stabilize the G-quadruplex structure. CONCLUSIONS: Three natural small molecules were found to have very high binding affinities to the mRNA G-quadruplex and stabilize this structure. The properties of these alkaloids revealed promising potentials to regulate the expression of the BCL2 protein from the posttranscriptional pathway.
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