Embryonic stem cells maintain high origin activity and slow forks to coordinate replication with cell cycle...

Area of Science:

• Cell Biology
• Molecular Biology
• Genetics

Background:

• Embryonic stem (ES) cells are pluripotent and proliferate rapidly, suggesting high intrinsic replication stress.
• Understanding DNA replication dynamics in pluripotent stem cells is crucial for developmental biology and regenerative medicine.

Purpose of the Study:

• To investigate and compare replication fork dynamics in embryonic stem (ES) cells versus non-pluripotent cells.
• To elucidate the mechanisms underlying DNA replication control in pluripotent stem cells.

Main Methods:

• Analysis of replication fork speed and origin density across S phase substages.
• Investigation of ATR-dependent regulation of replication fork dynamics.
• Assessment of genome stability following nucleoside addition to alter replication parameters.

Main Results:

• Pluripotent stem cells exhibit slow replication fork speeds and high active origin density throughout S phase with minimal pausing.
• Non-pluripotent cells show initial slow fork speed and increased pausing, followed by accelerated fork speed and reduced pausing in an ATR-dependent manner.
• Nucleoside addition accelerates fork speed and reduces origin density but leads to genome instability due to replication-cell cycle miscoordination.

Conclusions:

• Replication fork dynamics differ significantly between pluripotent (ES) and non-pluripotent cells.
• Slow replication fork speed and high origin density are integral to maintaining genome stability in pluripotent stem cells.
• The observed replication strategy in ES cells is a protective mechanism against replication stress inherent to rapid proliferation.