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Defective S phase chromatin assembly causes DNA damage, activation of the S phase checkpoint, and S phase arrest
Xiaofen Ye1, Alexa A Franco, Hidelita Santos
1Division of Basic Science, Fox Chase Cancer Center, Philadelphia, PA 19111, USA.
Abstract:
The S phase checkpoint protects the genome from spontaneous damage during DNA replication, although the cause of damage has been unknown. We used a dominant-negative mutant of a subunit of CAF-I, a complex that assembles newly synthesized DNA into nucleosomes, to inhibit S phase chromatin assembly and found that this induced S phase arrest. Arrest was accompanied by DNA damage and S phase checkpoint activation and required ATR or ATM kinase activity. These results show that in human cells CAF-I activity is required for completion of S phase and that a defect in chromatin assembly can itself induce DNA damage. We propose that errors in chromatin assembly, occurring spontaneously or caused by genetic mutations or environmental agents, contribute to genome instability.
Insights
Defects in chromatin assembly during DNA replication trigger genome-wide damage and cell cycle arrest. This study reveals that CAF-I activity is crucial for preventing DNA damage and maintaining genome stability.
Area of Science:
- Cell Biology
- Genetics
- Molecular Biology
Background:
- The S phase checkpoint safeguards the genome during DNA replication.
- The precise causes of spontaneous DNA damage during S phase have remained unclear.
Purpose of the Study:
- To investigate the role of chromatin assembly in S phase checkpoint activation.
- To determine if defects in chromatin assembly can directly cause DNA damage.
Main Methods:
- Utilized a dominant-negative mutant of a CAF-I subunit to inhibit chromatin assembly.
- Monitored S phase progression, DNA damage markers, and checkpoint activation.
- Assessed the requirement for ATR/ATM kinase activity.
Main Results:
- Inhibition of CAF-I-mediated chromatin assembly induced S phase arrest.
- The S phase arrest was associated with significant DNA damage.
- ATR/ATM kinase activity was essential for the observed S phase arrest and DNA damage response.
Conclusions:
- CAF-I activity is essential for the timely completion of S phase in human cells.
- Impaired chromatin assembly is a direct source of DNA damage.
- Errors in chromatin assembly may contribute to genome instability.