title: Amide bond direction modulates G-quadruplex recognition and telomerase inhibition by 2,6 and 2,7 bis-substituted anthracenedione derivatives.
abstract: G-quadruplex structures of DNA represent a potentially useful target for anticancer drugs. Stabilisation of this arrangement at the ends of chromosomes may inhibit the action of telomerase, an enzyme involved in immortalization of cancer cells. Appropriately substituted amido anthracenediones are effective G-quadruplex stabilizers, but no information is available as yet on the possible modulation of G-quadruplex recognition and telomerase inhibition produced by the direction of the amide bond. To understand the basis of amido anthracenedione selectivity, we have synthesized a number of derivatives bearing the -CO-NH- or -NH-CO- group linked to the planar anthraquinone (AQ) moiety at 2,6 and 2,7 positions. The various isomers were tested in terms of telomerase inhibition, determined by the TRAP assay, G-quadruplex stabilisation measured by the increase in melting temperature of the appropriately folded oligonucleotide using FRET, and conformational and G4 binding properties examined by molecular modelling techniques. In all cases, enzymatic inhibition and G-quadruplex stabilization were directly related, which strongly supports the proposed molecular mechanism of telomerase interference. Interestingly, the AQ-NH-CO- arrangement performs invariantly better than the AQ-CO-NH- arrangement, showing a clear preference among isomeric derivatives. Theoretical calculations suggest that the former amide arrangement is co-planar with the aromatic system, whereas the latter is tilted by about 30 degrees when considering the most stable conformation. A more extended planar surface would allow more efficient stacking interactions with the quadruplex structure, hence more effective telomerase inhibition.
authors.affiliation: Department of Pharmaceutical Sciences, University of Padova, Via Marzolo, 5, 35131 Padova, Italy.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Zagotto
authors.forename: Claudia
authors.initials: C
authors.lastname: Sissi
authors.forename: Stefano
authors.initials: S
authors.lastname: Moro
authors.forename: Diego
authors.initials: D
authors.lastname: Dal Ben
authors.forename: Gary N
authors.initials: GN
authors.lastname: Parkinson
authors.forename: Keith R
authors.initials: KR
authors.lastname: Fox
authors.forename: Stephen
authors.initials: S
authors.lastname: Neidle
authors.forename: Manlio
authors.initials: M
authors.lastname: Palumbo
mesh_terms: D000577:Amides / Q000737:chemistry; D000880:Anthraquinones / Q000737:chemistry* / Q000494:pharmacology*; D045744:Cell Line, Tumor; D031541:Fluorescence Resonance Energy Transfer; D054856:G-Quadruplexes; D006801:Humans; D007536:Isomerism; D008958:Models, Molecular; D009690:Nucleic Acid Conformation; D013329:Structure-Activity Relationship; D019098:Telomerase / Q000037:antagonists & inhibitors*; D013696:Temperature
chemical_list: D000577:Amides; D000880:Anthraquinones; D019098:Telomerase