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== DNA Replication Stress ==

[[File:Replication_stress_and_its_consequences_in_mitosis.png|Replication stress and its consequences in mitosis|thumb|right]]

'''DNA replication stress''' refers to the slowing or stalling of the [[DNA replication]] process, which can lead to genomic instability. This phenomenon is a significant concern in both normal cellular processes and in the context of [[cancer]] development. Replication stress can arise from various sources, including DNA damage, difficult-to-replicate sequences, and insufficient supply of deoxyribonucleotide triphosphates (dNTPs).

== Causes of DNA Replication Stress ==

Replication stress can be induced by several factors:

* '''DNA Damage:''' Lesions such as [[thymine dimers]] or [[double-strand breaks]] can impede the progression of the [[replication fork]].
* '''Replication Fork Barriers:''' Natural barriers such as [[telomeres]], [[centromeres]], and highly transcribed regions can cause stalling.
* '''Oncogene Activation:''' Overexpression of oncogenes can lead to increased replication origin firing, depleting dNTP pools and causing stress.
* '''Chromatin Structure:''' Tight chromatin can hinder the progression of replication machinery.

== Consequences of Replication Stress ==

[[File:INO80_stabilizes_replication_forks_and_counteracts_mislocalization_of_H2A.Z.png|INO80 stabilizes replication forks and counteracts mislocalization of H2A.Z|thumb|left]]

When replication stress occurs, it can lead to several cellular consequences:

* '''Fork Collapse:''' Prolonged stalling can result in the collapse of replication forks, leading to [[double-strand breaks]].
* '''Genomic Instability:''' Accumulation of DNA damage and improper repair can cause mutations and chromosomal rearrangements.
* '''Cell Cycle Arrest:''' Activation of the [[DNA damage response]] can halt the cell cycle to allow for repair.
* '''Apoptosis:''' If damage is irreparable, cells may undergo programmed cell death.

== Cellular Responses to Replication Stress ==

Cells have evolved mechanisms to cope with replication stress:

* '''Checkpoint Activation:''' The [[ATR]] and [[CHK1]] pathways are crucial for detecting and responding to replication stress.
* '''Fork Stabilization:''' Proteins such as [[BRCA1]] and [[BRCA2]] help stabilize stalled forks and facilitate repair.
* '''Translesion Synthesis:''' Specialized [[DNA polymerases]] can bypass lesions to allow replication to continue.

== Replication Stress in Cancer ==

[[File:Rationale_for_enhancing_replication_stress_to_kill_cancer_cells.png|Rationale for enhancing replication stress to kill cancer cells|thumb|right]]

Replication stress is a hallmark of cancer cells, which often exhibit high levels of genomic instability. Cancer cells frequently experience replication stress due to:

* '''Oncogene-Induced Replication Stress:''' Oncogenes can drive excessive replication, leading to stress.
* '''Defective DNA Repair:''' Many cancer cells have mutations in DNA repair pathways, exacerbating stress.

== Therapeutic Targeting of Replication Stress ==

[[File:Illustration_of_various_approaches_to_target_replication_stress_for_cancer_treatment.png|Illustration of various approaches to target replication stress for cancer treatment|thumb|left]]

Exploiting replication stress is a promising strategy in cancer therapy:

* '''PARP Inhibitors:''' These drugs target cancer cells with defective [[homologous recombination]] repair.
* '''ATR/CHK1 Inhibitors:''' Inhibiting these pathways can enhance replication stress, selectively killing cancer cells.
* '''dNTP Pool Modulation:''' Altering nucleotide availability can increase stress in cancer cells.

== Related Pages ==

* [[DNA replication]]
* [[Genomic instability]]
* [[DNA damage response]]
* [[Cancer]]

[[Category:DNA replication]]
[[Category:Genomic instability]]
[[Category:Cancer biology]]

DNA replication stress - Revision history

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