Related Experiment Videos
Increased sequence-specific p53-DNA binding activity after DNA damage is attenuated by phorbol esters
1Stress Protein Group, Dana-Farber Cancer Institute, Boston, Massachusetts 02115.
Abstract:
Damage to cellular DNA greatly increases the levels of the tumor-suppressor gene p53 and induces cell cycle arrest in G1. A critical function of wild-type p53 is its ability to bind to specific DNA sequences. The effect of DNA damage on the sequence-specific DNA-binding properties of cellular p53 was investigated using DNA gel mobility-shift assays with nuclear extracts from NIH-3T3 cells. DNA damage (initiated by radiation) induced a rapid, cycloheximide-sensitive increase in the levels of nuclear p53-DNA binding activity and an increase in the half-life of the p53 protein. Increased p53-DNA binding activity could be detected at low (0.2 Gy), non-lethal doses of radiation. The tumor promoter 12-O-tetradecanoyl phorbol 13-acetate (TPA) attenuated the DNA damage-induced increase in p53-DNA binding activity by decreasing the half-life of the p53 protein. The tumor promoter properties of TPA may therefore be mediated by interfering with the cellular p53 response to DNA damage. The increased levels of p53 bound to specific DNA sequences following DNA damage may induce cell cycle arrest. p53-mediated growth arrest could occur by inhibition of DNA replication and/or alterations in transcription of cell cycle genes.
Insights
DNA damage rapidly increases tumor suppressor p53 protein binding to DNA, triggering cell cycle arrest. Tumor promoters like TPA can interfere with this critical DNA damage response pathway.
Area of Science:
- Molecular Biology
- Cell Biology
- Cancer Research
Background:
- The tumor-suppressor gene p53 plays a crucial role in cellular response to DNA damage.
- Wild-type p53's function involves binding to specific DNA sequences to regulate cellular processes.
- DNA damage is known to elevate p53 levels and induce cell cycle arrest.
Purpose of the Study:
- To investigate the impact of DNA damage on the sequence-specific DNA-binding properties of cellular p53.
- To determine how tumor promoters affect the p53-DNA binding activity in response to DNA damage.
Main Methods:
- Utilized DNA gel mobility-shift assays with nuclear extracts from NIH-3T3 cells.
- Investigated the effects of radiation-induced DNA damage and the tumor promoter TPA on p53 activity.
- Measured changes in p53 protein levels and half-life.
Main Results:
- Radiation-induced DNA damage caused a rapid, cycloheximide-sensitive increase in nuclear p53-DNA binding activity.
- The half-life of the p53 protein increased following DNA damage, even at low radiation doses.
- The tumor promoter TPA decreased p53-DNA binding activity by reducing p53 protein half-life.
Conclusions:
- The cellular p53 response to DNA damage involves increased sequence-specific DNA binding activity.
- Tumor promoters like TPA may exert their effects by disrupting the p53-mediated DNA damage response.
- Elevated p53 binding to DNA post-damage likely contributes to cell cycle arrest, potentially via regulating DNA replication and cell cycle gene transcription.