Simple, PCR-free telomerase activity detection using G-quadruplex–hemin DNAzyme

Abstract

A simple, cost-effective and polymerase chain reaction (PCR)-free telomerase activity detection method was developed on the basis of telomerase-triggered formation of G-quadruplex–hemin DNAzyme. In this method, a short, unlabelled telomerase primer was used. Because this primer contains only three GGG repeats, it cannot fold into the stable G-quadruplex structure. In the presence of active telomerase and dGTP, a GGG repeat is added to the 3′-end of the primer. The extended primer can fold into the G-quadruplex, which is able to bind hemin to form catalytically active G-quadruplex–hemin DNAzyme, catalyzing the oxidation of 2,2′-azinobis (3-ethylbenzothiozoline)-6-sulfonic acid (ABTS) by H₂O₂ to green ABTS˙⁺. Because the primer extension product is very short, telomerase should show a high turnover rate, thus providing the method with improved sensitivity. Using this method, the telomerase activity originating from 200 HeLa cells can be detected.