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Related Concept Videos

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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...
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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.
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Translesion DNA Polymerases02:10

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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.
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In response to DNA damage, cells can pause the cell cycle to assess and repair the breaks. However, the cell must check the DNA at certain critical stages during the cell cycle. If the cell cycle pauses before DNA replication, the cells will contain twice the amount of DNA. On the other hand, if cells arrest after DNA replication but before mitosis, they will contain four times the normal amount of DNA. With a host of specialized proteins at their disposal,cells must use the right protein at...
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DNA replication is initiated at sites containing predefined DNA sequences known as origins of replication. DNA is unwound at these sites by the minichromosome maintenance (MCM) helicase and other factors such as Cdc45 and the associated GINS complex.The unwound single strands are protected by replication protein A (RPA) until DNA polymerase starts synthesizing DNA at the 5’ end of the strand in the same direction as the replication fork. To prevent the replication fork from falling apart,...
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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...
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Related Experiment Video

Updated: Jul 21, 2025

Author Spotlight: Advanced Single-Molecule Techniques for Investigating Telomeric Protein-DNA Interactions
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Author Spotlight: Advanced Single-Molecule Techniques for Investigating Telomeric Protein-DNA Interactions

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CST-Polα/Primase: the second telomere maintenance machine.

Sarah W Cai1, Titia de Lange2

  • 1Laboratory for Cell Biology and Genetics, The Rockefeller University, New York, New York 10065, USA.

Genes & Development
|July 26, 2023
PubMed
Summary
This summary is machine-generated.

Telomeres require both telomerase and the CST-Polα/Primase complex for complete maintenance. This complex replenishes lost 5' telomere sequences and regulates telomere length, preventing overextension by telomerase.

Keywords:
CSTtelomerasetelomere

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Telomere Length and Telomerase Activity; A Yin and Yang of Cell Senescence
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Telomere Length and Telomerase Activity; A Yin and Yang of Cell Senescence

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Area of Science:

  • Molecular Biology
  • Genetics
  • Cell Biology

Background:

  • Telomerase extends the 3' end of eukaryotic chromosomes, using its RNA template.
  • Lagging strand DNA synthesis and nucleolytic processing lead to sequence loss at the 5' telomere ends.
  • A second enzyme system is necessary to maintain the integrity of the 5' telomere ends.

Purpose of the Study:

  • To discuss recent data on the evolution, structure, function, and recruitment of mammalian CST-Polα/Primase.
  • To highlight the role of the CST-Polα/Primase complex in telomere maintenance and length control.
  • To emphasize the connection between telomere length regulation and human disease.

Main Methods:

  • Review of recent data on CST-Polα/Primase.
  • Analysis of telomere maintenance mechanisms.
  • Discussion of telomere length control in mammals.

Main Results:

  • Telomerase alone cannot maintain telomere 5' ends.
  • The Ctc1-Stn1-Ten1 (CST) complex bound to DNA polymerase α/Primase (Polα/Primase) replenishes lost 5' telomere sequences via a fill-in reaction.
  • CST-Polα/Primase also regulates telomere length by preventing telomerase overelongation.

Conclusions:

  • The CST-Polα/Primase complex is essential for complete telomere maintenance, complementing telomerase activity.
  • This complex plays a critical role in controlling telomere length.
  • Dysregulation of CST-Polα/Primase and telomere length control is implicated in human diseases.