Nucleic Acids Research, Vol 27, Issue 4 1152-1158, Copyright © 1999 by Oxford University Press
E Matthes and C Lehmann
Human telomerase is a ribonucleoprotein which uses its internal RNA moiety
as a template for telomeric DNA synthesis. This enzyme is up- regulated in
most malignant tumors and is therefore considered as a possible cancer
target. Here we examined the effects of differently modified oligomers on
telomeraseactivity from HL-60 cell extracts (TRAP- ezetrade mark assay).
Phosphorothioate-modified oligonucleotides (PS- ODNs) inhibited telomerase
activity at subnanomolar concen-trations and proved to be more efficient
than peptide nucleic acids. In contrast to all the investigated oligomers,
PS-ODNs were found to bind to the protein motif of telomerase called the
primer binding site but poorly to its RNA. This is suggested by kinetic
investigations demonstrating a competitive interaction of PS-ODNs and TS
primer at the primer binding site. The K m value of the TS primer was 10.8
nM, the K i value of a 20mer PS-ODN was 1.6 nM. When the TS primer was
PS-modified a striking increase in the telomerase activity was found which
correlates with the number of phosphodiesters replaced. The K m value of a
completely PS- modified TS primer was 0.56 nM. Based on these results the
design of chimeric ODNs is proposed consisting of a 5'-PS-modified part
targeting the primer binding site and a 3'-terminus part targeting the
telomerase RNA.
ARTICLES
Telomerase protein rather than its RNA is the target of phosphorothioate-modified oligonucleotides
Max-Delbruck-Centrum fur Molekulare Medizin, Robert-R ossle-Strasse 10, D-13092 Berlin, Germany. emat@mdc-berlin.de
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