Related Experiment Video

Updated: Sep 29, 2026

Detection of Aggregation-Prone Behavior in Mutant P53 V157F Breast Cancer Cells Using Multipoint Thioflavin T Fluorescence
04:56

Detection of Aggregation-Prone Behavior in Mutant P53 V157F Breast Cancer Cells Using Multipoint Thioflavin T Fluorescence

Published on: December 30, 2025

Mdm-2 binding and TAF(II)31 recruitment is regulated by hydrogen bond disruption between the p53 residues Thr18 and

James R Jabbur1, Amy D Tabor, Xiaodong Cheng

  • 1Department of Pathology, The University of Texas M.D. Anderson Cancer Center, Houston, Texas, TX 77030, USA.

Oncogene
|October 10, 2002
PubMed

Insights

Phosphorylation of Thr18 in p53 protein enhances its tumor suppressor activity by disrupting Mdm-2 binding, leading to increased p21 expression. This finding is crucial for understanding p53’s role in cancer.

Area of Science:

  • Molecular Biology
  • Cancer Research
  • Protein Biochemistry

Background:

  • The tumor suppressor protein p53 plays a critical role in cellular responses to DNA damage.
  • Post-translational modifications, such as phosphorylation, regulate p53 activity and stability.
  • Specific phosphorylation sites, like Thr18, are implicated in modulating p53's transactivation function.

Purpose of the Study:

  • To investigate the role of Thr18 phosphorylation in p53 transactivation.
  • To elucidate the mechanism by which Thr18 phosphorylation affects p53 interactions with Mdm-2 and TAFII31.
  • To determine the functional consequence of disrupting the Thr18-Asp21 hydrogen bond on p53-mediated gene expression.

Main Methods:

  • Analysis of p53 phosphorylation in wild-type cell lines after ionizing (IR) and ultraviolet (UV) radiation.
  • Site-directed mutagenesis to disrupt the hydrogen bond between Thr18 and Asp21.
  • Co-immunoprecipitation assays to assess protein-protein interactions (p53-Mdm-2, p53-TAFII31).
  • Transfection studies in p53-null and p53/Mdm-2-double null cells to evaluate p21 induction.

Main Results:

  • Thr18 phosphorylation in p53 correlated with the induction of downstream targets p21(Waf1/Cip1) (p21) and Mdm-2.
  • Disruption of the Thr18-Asp21 hydrogen bond attenuated p53 interaction with Mdm-2 but not TAFII31.
  • Mdm-2 was shown to inhibit p53 interaction with TAFII31.
  • p53-null cells expressing Thr18-Asp21 hydrogen bond disrupting mutants showed enhanced p21 expression.

Conclusions:

  • Disruption of the intramolecular hydrogen bond between Thr18 and Asp21 enhances p53 transactivation.
  • This enhancement is mediated by modulating Mdm-2 binding, which facilitates TAFII31 recruitment.
  • The findings provide a mechanistic insight into how p53 activity is regulated post-translationally for tumor suppression.

More Related Videos

Purification of Ubiquitinated p53 Proteins from Mammalian Cells10:55

Purification of Ubiquitinated p53 Proteins from Mammalian Cells

Published on: March 21, 2022

Related Concept Videos

Abnormal Proliferation02:23

Abnormal Proliferation

Under normal conditions, most adult cells remain in a non-proliferative state unless stimulated by internal or external factors to replace lost cells. Abnormal cell proliferation is a condition in which the cell's growth exceeds and is uncoordinated with normal cells. In such situations, cell division persists in the same excessive manner even after cessation of the stimuli, leading to persistent tumors. The tumor arises from the damaged cells that replicate to pass the damage to the daughter...
Covalently Linked Protein Regulators02:04

Covalently Linked Protein Regulators

Proteins can undergo many types of post-translational modifications, often in response to changes in their environment. These modifications play an important role in the function and stability of these proteins. Covalently linked molecules include functional groups, such as methyl, acetyl, and phosphate groups, and also small proteins, such as ubiquitin. There are around 200 different types of covalent regulators that have been identified.
These groups modify specific amino acids in a protein.
DNA Damage can Stall the Cell Cycle02:36

DNA Damage can Stall the Cell Cycle

In response to DNA damage, cells can pause the cell cycle to assess and repair the breaks. However, the cell must check the DNA at certain critical stages during the cell cycle. If the cell cycle pauses before DNA replication, the cells will contain twice the amount of DNA. On the other hand, if cells arrest after DNA replication but before mitosis, they will contain four times the normal amount of DNA. With a host of specialized proteins at their disposal,cells must use the right protein at...
DNA Damage Can Stall the Cell Cycle02:36

DNA Damage Can Stall the Cell Cycle

In response to DNA damage, cells can pause the cell cycle to assess and repair the breaks. However, the cell must check the DNA at certain critical stages during the cell cycle. If the cell cycle pauses before DNA replication, the cells will contain twice the amount of DNA. On the other hand, if cells arrest after DNA replication but before mitosis, they will contain four times the normal amount of DNA. With a host of specialized proteins at their disposal,cells must use the right protein at...
Master Transcription Regulators02:23

Master Transcription Regulators

Master transcription regulators are regulatory proteins that are predominantly responsible for regulating the expression of multiple genes. Often these genes work in concert to drive a  complex process. Activation of a master transcription regulator can lead to a cascade of transcriptional activation necessary for that outcome. These regulators can directly bind to the regulatory sequences of the various genes involved, or they can indirectly regulate transcription by binding to regulatory...
Negative Regulator Molecules01:23

Negative Regulator Molecules

Positive regulators allow a cell to advance through cell cycle checkpoints. Negative regulators have an equally important role as they terminate a cell’s progression through the cell cycle—or pause it—until the cell meets specific criteria.