Telomerase as a Potential Molecular Target to Study G-Quartet Phosphorothioates

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Abstract
Inhibition of gene expression by phosphorothioate oligomers is complex and involves specific and nonspecific mechanisms. Oligomers that contain a G-quartet elicit distinct effects in vitro and in vivo that are dependent on the context of the G-quartet's occurrence within a sequence. The enzyme telomerase, a ribonucleoprotein, has a stretch of C residues in the RNA template, which are used to add terminal dG-rich telomeric repeats to the ends of chromosomes. Some but not all phosphorothioates containing a G-quartet, depending on the context of occurrence, inhibited telomerase activity in vitro. Non-G-quartet phosphorothioates did not inhibit this activity. Activities of control enzymes, such as reverse transcriptase or taq polymerase, were not affected by the G-quartet oligomers. Neither phosphodiester nor chimeric oligomers of a G-quartet-containing oligomer were as potent inhibition of telomerase activity as phosphorothioate oligomers. These results may provide a molecular target to study the effects of G-quartet-containing oligomers.