A non-natural nucleotide uses a specific pocket to selectively inhibit telomerase activity

Area of Science:

• Biochemistry
• Molecular Biology
• Structural Biology

Background:

• Telomerase is a reverse transcriptase enzyme crucial for maintaining telomere length.
• Telomerase is frequently upregulated in cancer cells, making it a target for anti-cancer therapies.

Purpose of the Study:

• To investigate the potential of 5-methylcarboxyl-indolyl-2 -deoxyriboside 5 -triphosphate (5-MeCITP) as a telomerase inhibitor.
• To elucidate the mechanism of 5-MeCITP inhibition using structural and in vitro methods.

Main Methods:

• X-ray crystallography to determine the structure of 5-MeCITP bound to telomerase reverse transcriptase.
• In vitro enzymatic assays to measure telomerase inhibition potency.
• Cell-based assays to assess telomere shortening and cytotoxicity.

Main Results:

• 5-MeCITP binds to telomerase reverse transcriptase via an atypical interaction, with the nucleobase flipped in the active site.
• The methoxy group of 5-MeCITP interacts with a specific hydrophobic pocket on the telomerase enzyme.
• 5-MeCITP demonstrated comparable telomerase inhibition potency to azidothymidine (AZT) in vitro.
• Cell-permeable 5-MeCITP induced telomere shortening in cancer cells with lower cytotoxicity than AZT.

Conclusions:

• 5-MeCITP is a potent telomerase inhibitor with a unique binding mechanism.
• 5-MeCITP exhibits potential as a targeted anti-cancer therapeutic agent due to its efficacy and reduced toxicity profile.