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p53 Monitors replication fork regression by binding to "chickenfoot" intermediates

Deepa Subramanian1, Jack D Griffith

  • 1Lineberger Comprehensive Cancer Center and Department of Microbiology and Immunology, University of North Carolina, Chapel Hill, North Carolina 27599, USA.

The Journal of Biological Chemistry
|October 6, 2005
PubMed

Insights

The tumor suppressor protein p53 binds stalled DNA replication forks, crucial for genomic integrity. Cancer-linked p53 mutations weaken this essential DNA binding interaction.

Area of Science:

  • Molecular Biology
  • Genetics
  • Biochemistry

Background:

  • The p53 protein is a critical tumor suppressor involved in maintaining genomic stability.
  • p53 regulates DNA replication, repair, and recombination, processes vital for preventing mutations.
  • Understanding how p53 interacts with DNA intermediates is key to its function.

Purpose of the Study:

  • To investigate the direct binding of p53 to DNA structures resembling stalled replication forks.
  • To analyze the interaction of wild-type p53 and cancer-derived mutants with these DNA structures.

Main Methods:

  • Generation of DNA templates mimicking stalled replication forks.
  • Utilized electron microscopy to visualize and quantify p53 binding to DNA substrates.
  • Assessed binding affinity of wild-type p53 and two cancer-derived mutants.

Main Results:

  • p53 exhibited high-affinity binding to the junction of stalled replication fork DNA templates.
  • Two cancer-associated p53 mutants displayed significantly reduced binding affinity.
  • p53 binding induced rearrangement of DNA templates into 'chickenfoot' structures, primarily by trapping intermediates of fork regression.

Conclusions:

  • Sequence-independent binding of p53 to stalled replication forks is crucial for genomic integrity.
  • Mutations in p53 can impair its ability to interact with critical DNA structures, potentially contributing to cancer development.
  • p53 plays a role in stabilizing or even promoting the formation of specific DNA structures during replication stress.

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