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Study of the DNA Damage Checkpoint using Xenopus Egg Extracts
10:55

Study of the DNA Damage Checkpoint using Xenopus Egg Extracts

Published on: November 5, 2012

Direct requirement for Xmus101 in ATR-mediated phosphorylation of Claspin bound Chk1 during checkpoint signaling

Shan Yan1, Howard D Lindsay, W Matthew Michael

  • 1The Biological Laboratories, Harvard University, Cambridge, MA 02138, USA.

The Journal of Cell Biology
|April 19, 2006
PubMed

Insights

TopBP1-like proteins, including Xmus101, are crucial for DNA replication and checkpoint control. This study reveals Xmus101 directly relays signals from ATR to Chk1, essential for activating the DNA replication checkpoint.

Area of Science:

  • Molecular Biology
  • Cell Cycle Regulation
  • DNA Replication and Repair

Background:

  • TopBP1-like proteins, such as Xenopus laevis Xmus101, are implicated in DNA replication and checkpoint control.
  • Proving a direct role in checkpoint control is challenging due to the need for replication to activate checkpoints.

Purpose of the Study:

  • To elucidate the direct role of Xmus101 in DNA replication checkpoint signaling.
  • To investigate Xmus101 function independently of DNA replication.

Main Methods:

  • Utilized Xenopus laevis egg extracts with AT70 oligonucleotide duplex to trigger replication-independent checkpoint activation.
  • Employed a separation-of-function mutant of Xmus101 to dissect its role in checkpoint signaling.

Main Results:

  • Xmus101 is essential for AT70-mediated checkpoint activation.
  • Xmus101 promotes the phosphorylation of Claspin-bound Chk1 by ATR kinase.
  • A separation-of-function Xmus101 mutant allowed normal replication but abolished checkpoint response to stalled forks.

Conclusions:

  • Xmus101 plays a direct role in the DNA replication checkpoint.
  • Xmus101 functions in signal relay from ATR to Chk1 during checkpoint activation.

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