Related Experiment Video
Updated: May 21, 2026
12:08
Telomere Length and Telomerase Activity; A Yin and Yang of Cell Senescence
Published on: May 22, 2013
Timeless preserves telomere length by promoting efficient DNA replication through human telomeres.
Adam R Leman1, Jayaraju Dheekollu, Zhong Deng
1Department of Biochemistry and Molecular Biology, Drexel University College of Medicine, Philadelphia, PA, USA.
Cell Cycle (Georgetown, Tex.)
|June 8, 2012
Summary
The Timeless protein is crucial for maintaining telomere length in human cells. Its depletion causes telomere shortening and DNA damage, highlighting its role in genomic stability.
Area of Science:
- Genetics
- Molecular Biology
- Cell Biology
Background:
- Telomere maintenance is vital for genomic stability but remains incompletely understood.
- The Timeless protein is known to associate with replication forks but its specific role at telomeres is unclear.
Purpose of the Study:
- To investigate the role of the Timeless protein in telomere length maintenance.
- To elucidate the mechanism by which Timeless regulates telomere structure and integrity.
Main Methods:
- Depletion of Timeless protein in human cells.
- Assessment of telomere length and DNA damage.
- In vitro telomere replication assays.
- Analysis of interactions with Shelterin components TRF1 and TRF2.
Main Results:
- Timeless depletion led to significant telomere shortening and increased DNA damage.
- Telomere length maintenance was independent of telomerase.
- Timeless interacts with TRF1 and TRF2, and its absence slows telomere replication.
- Cells lacking Timeless showed impaired TRF1-mediated accumulation of replication machinery at telomeres.
Conclusions:
- Timeless is essential for maintaining telomere length and integrity in human cells.
- Timeless functions with TRF1 to prevent replication fork collapse at telomeres.
- This mechanism ensures stable telomere maintenance, independent of telomerase.
Related Concept Videos
02:41Telomeres 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.
02:41Telomeres 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.
01:29Replication 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...
Many Proteins Orchestrate Replication at the Origin
Eukaryotic replication follows many of the same...
02:31Replication in Eukaryotes
Overview
02:15Replicative Cell Senescence
Replicative cell senescence is a property of cells that allows them to divide a finite number of times throughout the organism's lifespan while preventing excessive proliferation. Replicative senescence is associated with the gradual loss of the telomere — short, repetitive DNA sequences found at the end of the chromosomes. Telomeres are bound by a group of proteins to form a protective cap on the ends of chromosomes. Embryonic stem cells express telomerase — an enzyme that adds the telomeric...
02:15Replicative Cell Senescence
Replicative cell senescence is a property of cells that allows them to divide a finite number of times throughout the organism's lifespan while preventing excessive proliferation. Replicative senescence is associated with the gradual loss of the telomere — short, repetitive DNA sequences found at the end of the chromosomes. Telomeres are bound by a group of proteins to form a protective cap on the ends of chromosomes. Embryonic stem cells express telomerase — an enzyme that adds the telomeric...