Checkpoint silencing during the DNA damage response in Caenorhabditis elegans embryos
Antonia H Holway1, Seung-Hwan Kim, Adriana La Volpe
1The Biological Laboratories, Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA.
Abstract:
In most cells, the DNA damage checkpoint delays cell division when replication is stalled by DNA damage. In early Caenorhabditis elegans embryos, however, the checkpoint responds to developmental signals that control the timing of cell division, and checkpoint activation by nondevelopmental inputs disrupts cell cycle timing and causes embryonic lethality. Given this sensitivity to inappropriate checkpoint activation, we were interested in how embryos respond to DNA damage. We demonstrate that the checkpoint response to DNA damage is actively silenced in embryos but not in the germ line. Silencing requires rad-2, gei-17, and the polh-1 translesion DNA polymerase, which suppress replication fork stalling and thereby eliminate the checkpoint-activating signal. These results explain how checkpoint activation is restricted to developmental signals during embryogenesis and insulated from DNA damage. They also show that checkpoint activation is not an obligatory response to DNA damage and that pathways exist to bypass the checkpoint when survival depends on uninterrupted progression through the cell cycle.
Insights
Early embryos actively silence DNA damage checkpoints, preventing cell cycle delays. This ensures proper development by suppressing DNA damage responses, unlike germline cells.
Area of Science:
- Cell Biology
- Developmental Biology
- Genetics
Background:
- The DNA damage checkpoint typically halts cell division upon detecting DNA damage to allow for repair.
- In early Caenorhabditis elegans embryos, this checkpoint is sensitive to developmental signals, and inappropriate activation leads to embryonic lethality.
- Understanding how embryos handle DNA damage is crucial given their sensitivity to checkpoint dysregulation.
Purpose of the Study:
- To investigate the response of early Caenorhabditis elegans embryos to DNA damage.
- To determine the mechanisms underlying the selective silencing of the DNA damage checkpoint in embryos.
Main Methods:
- Genetic analysis in Caenorhabditis elegans.
- Investigating the roles of specific genes (rad-2, gei-17) and a translesion DNA polymerase (polh-1) in checkpoint regulation.
- Assessing replication fork stalling and checkpoint activation.
Main Results:
- The DNA damage checkpoint response is actively silenced in early embryos but not in the germline.
- Silencing requires the genes rad-2, gei-17, and the polh-1 translesion DNA polymerase.
- These factors suppress replication fork stalling, thereby preventing checkpoint activation by DNA damage.
Conclusions:
- Embryonic DNA damage checkpoint silencing ensures proper cell cycle timing by insulating it from DNA damage signals.
- Checkpoint activation is not an obligatory response to DNA damage; bypass pathways exist.
- This mechanism allows for uninterrupted cell cycle progression crucial for embryonic development.
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