Oxidative guanine base damage regulates human telomerase activity

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• Telomere length is critical for cellular aging and is implicated in cancer and degenerative diseases.
• Oxidative stress and DNA damage are known to influence telomere dynamics, leading to both elongation and shortening.
• The specific role of oxidative lesions in regulating telomere maintenance by human telomerase requires further elucidation.

Purpose of the Study:

• To investigate how the oxidative lesion 8-oxo-7,8-dihydro-2 '-deoxyguanine (8-oxoG) affects human telomerase activity and telomere elongation.
• To determine the impact of 8-oxoG's presence in the nucleotide pool versus within telomeric DNA on telomere maintenance.
• To explore the consequences of MTH1 depletion, which increases oxidized nucleotides, on telomere integrity in cancer cells.

Main Methods:

• Assessing telomerase activity in the presence of 8-oxodGTP (the oxidized form of 8-oxoG in the dNTP pool).
• Evaluating telomere dysfunction and cell death in cancer cells with depleted MTH1.
• Analyzing the effect of pre-existing 8-oxoG within telomeric DNA on telomerase function and G-quadruplex stability.

Main Results:

• Incorporation of 8-oxodGTP by telomerase is mutagenic and halts further telomere elongation.
• Depletion of MTH1 leads to increased telomere dysfunction and cell death in cancer cells.
• 8-oxoG lesions within telomeric DNA can promote telomerase activity by destabilizing G-quadruplex structures.

Conclusions:

• The biological outcome of 8-oxoG on telomere length is dependent on its origin: incorporation from the nucleotide pool inhibits telomerase, while direct presence in telomeric DNA can stimulate it.
• The dual role of 8-oxoG in telomere regulation highlights its complex involvement in maintaining genomic stability and its potential as a therapeutic target in cancer.
• Understanding the precise mechanism of 8-oxoG formation and its location is crucial for predicting its effect on telomere length and cellular fate.