Rad53 limits CMG helicase uncoupling from DNA synthesis at replication forks

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• DNA replication requires precise coordination between helicase unwinding and polymerase synthesis.
• Replication stress disrupts this balance, leading to fork defects and checkpoint activation.
• The Rad53 checkpoint kinase stabilizes stalled forks, but its mechanism remains unclear.

Purpose of the Study:

• To elucidate the mechanism by which the Rad53 checkpoint kinase stabilizes stalled replication forks.
• To investigate the coupling between helicase and polymerase activities at the replication fork.

Main Methods:

• Reconstitution of budding yeast replisomes in vitro.
• Investigating the effects of Pol ε inactivation, dNTP depletion, and polymerase inhibition on fork dynamics.
• Assessing the impact of Rad53 on CMG helicase activity.

Main Results:

• Budding yeast replisomes exhibit excessive DNA unwinding when leading strand polymerase (Pol ε) is inactivated or dNTPs are depleted.
• These conditions reveal a lack of intrinsic helicase-polymerase coupling control in yeast replisomes.
• Rad53 kinase activity was found to restrict excessive CMG helicase unwinding.

Conclusions:

• Rad53 limits CMG helicase activity to prevent excessive unwinding at stressed replication forks.
• This regulation by Rad53 provides a mechanism for replication fork stabilization.
• The findings highlight the crucial role of the replication checkpoint in maintaining genome stability.