Reevaluation of telomerase inhibition by quadruplex ligands and their mechanisms of action.
Quadruplex ligands are often considered as telomerase inhibitors. Given the fact that some of these molecules are present in the clinical setting, it is important to establish the validity of this assertion. To analyze the effects of these compounds, we used a direct assay with telomerase-enriched extracts. The comparison of potent ligands from various chemical families revealed important differences in terms of effects on telomerase initiation and processivity. Although most quadruplex ligands may lock a quadruplex-prone sequence into a quadruplex structure that inhibits the initiation of elongation by telomerase, the analysis of telomerase-elongation steps revealed that only a few molecules interfered with the processivity of telomerase (i.e., inhibit elongation once one or more repeats have been incorporated). The demonstration that these molecules are actually more effective inhibitors of telomeric DNA amplification than extension by telomerase contributes to the already growing suspicion that quadruplex ligands are not simple telomerase inhibitors but, rather, constitute a different class of biologically active molecules. We also demonstrate that the popular telomeric repeat amplification protocol is completely inappropriate for the determination of telomerase inhibition by quadruplex ligands, even when PCR controls are included. As a consequence, the inhibitory effect of many quadruplex ligands has been overestimated.
De Cian
Anne
A
Institut National de la Santé et de la Recherche Médicale, U565, F-75231 Paris Cedex 05, France.
Cristofari
Gael
G
Reichenbach
Patrick
P
De Lemos
Elsa
E
Monchaud
David
D
Teulade-Fichou
Marie-Paule
MP
Shin-Ya
Kazuo
K
Lacroix
Laurent
L
Lingner
Joachim
J
Mergny
Jean-Louis
JL
D001483:Base Sequence; D054856:G-Quadruplexes; D020128:Inhibitory Concentration 50; D008024:Ligands; D008969:Molecular Sequence Data; D013379:Substrate Specificity; D019098:Telomerase / Q000037:antagonists & inhibitors* / Q000378:metabolism*
D008024:Ligands; D019098:Telomerase