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Telomeres and Telomerase

Telomeres and Telomerase

In eukaryotic DNA replication, a single-stranded DNA fragment remains at the end of a chromosome after the removal of the final primer. This section of DNA cannot be replicated in the same manner as the rest of the strand because there is no 3’ end to which the newly synthesized DNA can attach. This non-replicated fragment results in gradual loss of the chromosomal DNA during each cell duplication. Additionally, it can induce a DNA damage response by enzymes that recognize single-stranded DNA.

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Updated: May 10, 2026

Analyzing Telomeric Protein-DNA Interactions Using Single-Molecule Magnetic Tweezers

Analyzing Telomeric Protein-DNA Interactions Using Single-Molecule Magnetic Tweezers

Published on: August 30, 2024

Rif1 and Rif2 shape telomere function and architecture through multivalent Rap1 interactions.

Tianlai Shi¹, Richard D Bunker, Stefano Mattarocci

¹Friedrich Miescher Institute for Biomedical Research, Maulbeerstrasse 66, 4058 Basel, Switzerland.

|June 11, 2013

Summary

Yeast telomeres are protected by the telosome, a complex of Rap1, Rif1, and Rif2 proteins. This study reveals how Rif1 and Rif2 create a higher-order structure that stabilizes Rap1, ensuring telomere length stability.

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Area of Science:

Molecular Biology
Biochemistry
Genetics

Background:

Yeast telomeres consist of TG₁₋₃ repeats and are bound by the transcription factor Rap1.
The telosome, composed of Rap1, Rif1, and Rif2, forms a protective cap on telomeres, regulating telomerase, silencing, and DNA break responses.

Purpose of the Study:

To elucidate the molecular architecture of the yeast telosome.
To understand the structural basis of Rap1 recruitment and stabilization by Rif1 and Rif2.

Main Methods:

X-ray crystallography to determine the structures of Rif1 and Rif2 bound to Rap1.
Biochemical and functional assays to dissect protein interactions and telomere homeostasis.

Main Results:

Crystal structures reveal independent Rap1-binding sites on Rif1 and Rif2, enabling long-range interactions.
Rif1 tetramerization and Rif2 polymerization modules contribute to a higher-order architecture that interlinks Rap1 units.
This 'molecular Velcro' mechanism is crucial for recruiting and stabilizing Rap1 on telomeres, maintaining telomere homeostasis.

Conclusions:

Rif1 and Rif2 form a higher-order structure that stabilizes Rap1 at yeast telomeres through long-range interactions.
This mechanism is essential for maintaining telomere length and overall telomere homeostasis in vivo.