A telomerase-associated RecQ protein-like helicase resolves telomeric G-quadruplex structures during replication

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• G-quadruplex DNA structures form at ciliate telomeres and are regulated by telomere-end-binding proteins (TEBPs).
• Telomeric G-quadruplex structures must be resolved for telomere replication by telomerase during the cell cycle.
• Phosphorylation of TEBPβ and telomerase binding are necessary but may not be sufficient for timely G-quadruplex unfolding.

Purpose of the Study:

• To identify and characterize a helicase involved in resolving telomeric G-quadruplex structures in vivo.
• To elucidate the mechanism by which G-quadruplex structures are unfolded to permit telomere replication.

Main Methods:

• In situ analyses and RNA interference (RNAi) for gene silencing.
• Co-immunoprecipitation experiments to assess protein interactions.
• In vitro assays using nuclear extracts from S-phase cells.

Main Results:

• A RecQ-like helicase, similar to human RecQ4, was identified as essential for in vivo G-quadruplex unfolding.
• This helicase associates with telomerase during replication and is recruited to telomeres by telomerase.
• Nuclear extracts containing both telomerase and the helicase effectively resolved telomeric G-quadruplex structures in vitro.

Conclusions:

• A novel RecQ-like helicase plays a crucial role in resolving telomeric G-quadruplex structures.
• The helicase functions in conjunction with telomerase, being recruited to telomeres by the enzyme.
• These findings contribute to a mechanistic model of telomeric G-quadruplex replication during the cell cycle.