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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.

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.

Translesion DNA Polymerases

Translesion DNA Polymerases

Translesion (TLS) polymerases rescue stalled DNA polymerases at sites of damaged bases by replacing the replicative polymerase and installing a nucleotide across the damaged site. Doing so, TLS allows additional time for the cell to repair the damage before resuming regular DNA replication.
TLS polymerases are found in all three domains of life - archaea, bacteria, and eukaryotes. Of the different classes of TLS polymerases, members of the Y family are fitted with specialized structures that...

Replication in Eukaryotes

Replication in Eukaryotes

In eukaryotic cells, DNA replication is highly conserved and tightly regulated. Multiple linear chromosomes must be duplicated with high fidelity before cell division, so there are many proteins that fulfill specialized roles in the replication process. Replication occurs in three phases: initiation, elongation, and termination, and ends with two complete sets of chromosomes in the nucleus.
Many Proteins Orchestrate Replication at the Origin
Eukaryotic replication follows many of the same...

Replication in Eukaryotes

Replication in Eukaryotes

Homologous Recombination

Homologous Recombination

The basic reaction of homologous recombination (HR) involves two chromatids that contain DNA sequences sharing a significant stretch of identity. One of these sequences uses a strand from another as a template to synthesize DNA in an enzyme-catalyzed reaction. The final product is a novel amalgamation of the two substrates. To ensure an accurate recombination of sequences, HR is restricted to the S and G2 phases of the cell cycle. At these stages, the DNA has been replicated already and the...

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Related Experiment Video

Updated: Jul 11, 2026

Single-Molecule Fluorescence Visualization of DNA Polymerase Dynamics at G-Quadruplexes

Single-Molecule Fluorescence Visualization of DNA Polymerase Dynamics at G-Quadruplexes

Published on: April 4, 2025

Telomerase recognizes G-quadruplex and linear DNA as distinct substrates.

Liana Oganesian¹, Mark E Graham, Phillip J Robinson

¹Children's Medical Research Institute, 214 Hawkesbury Road, Westmead NSW 2145, Australia and University of Sydney, NSW 2006, Australia.

|September 20, 2007

Summary

Tetrahymena telomerase (TERT) binds a novel G-quadruplex DNA structure. This G-quadruplex serves as a substrate for telomerase, impacting nucleotide binding and enzyme activity.

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In Vitro Chemical Mapping of G-Quadruplex DNA Structures by Bis-3-Chloropiperidines

Published on: May 12, 2023

Area of Science:

Molecular Biology
Biochemistry
Genetics

Background:

Telomeric DNA forms higher-order structures like G-quadruplexes.
Telomerase, including its catalytic subunit (TERT), plays a crucial role in maintaining telomeres.

Purpose of the Study:

To investigate the interaction between a specific telomeric G-quadruplex from Tetrahymena thermophila and TERT.
To elucidate the functional consequences of this interaction on telomerase activity.

Main Methods:

Electrospray ionization mass spectrometry to characterize the G-quadruplex structure.
Binding assays to determine TERT-G-quadruplex affinity.
In vitro telomerase extension assays using recombinant and cell extract-derived telomerase.
Site-directed mutagenesis (K538A) of TERT.

Main Results:

A novel parallel four-stranded G-quadruplex formed from Tetrahymena thermophila telomeric DNA was identified.
This G-quadruplex binds TERT with micromolar affinity, independent of telomerase RNA.
The G-quadruplex acts as a substrate for telomerase, affecting nucleotide binding and enzyme kinetics.
A specific TERT mutation (K538A) impaired G-quadruplex extension while retaining binding affinity.

Conclusions:

Telomerase recognizes and processes G-quadruplex DNA as a distinct substrate.
TERT undergoes conformational changes to accommodate G-quadruplex binding and extension.
The K538A mutation highlights the importance of specific TERT residues in G-quadruplex processing.