Related Experiment Video
Updated: Dec 7, 2025
High Sensitivity Measurement of Transcription Factor-DNA Binding Affinities by Competitive Titration Using Fluorescence Microscopy
Published on: February 7, 2019
Single molecule studies reveal that p53 tetramers dynamically bind response elements containing one or two half sites
Elina Ly1, Jennifer F Kugel2, James A Goodrich3
1Department of Biochemistry, University of Colorado Boulder, 596 UCB, Boulder, CO, 80309, USA.
Abstract:
The tumor suppressor protein p53 is critical for cell fate decisions, including apoptosis, senescence, and cell cycle arrest. p53 is a tetrameric transcription factor that binds DNA response elements to regulate transcription of target genes. p53 response elements consist of two decameric half-sites, and data suggest one p53 dimer in the tetramer binds to each half-site. Despite a broad literature describing p53 binding DNA, unanswered questions remain, due partly to the need for more quantitative and structural studies with full length protein. Here we describe a single molecule fluorescence system to visualize full length p53 tetramers binding DNA in real time. The data revealed a dynamic interaction in which tetrameric p53/DNA complexes assembled and disassembled without a dimer/DNA intermediate. On a wild type DNA containing two half sites, p53/DNA complexes existed in two kinetically distinct populations. p53 tetramers bound response elements containing only one half site to form a single population of complexes with reduced kinetic stability. Altering the spacing and helical phasing between two half sites affected both the population distribution of p53/DNA complexes and their kinetic stability. Our real time single molecule measurements of full length p53 tetramers binding DNA reveal the parameters that define the stability of p53/DNA complexes, and provide insight into the pathways by which those complexes assemble.
Insights
Full-length p53 tetramers bind DNA dynamically, forming distinct complex populations. This single-molecule study reveals how DNA structure influences p53/DNA complex stability and assembly pathways.
Area of Science:
- Molecular Biology
- Biochemistry
- Genetics
Background:
- The tumor suppressor protein p53 is a critical transcription factor regulating cell fate.
- p53 functions as a tetramer, binding specific DNA response elements to control gene expression.
- Previous studies on p53 DNA binding lack quantitative and structural data using the full-length protein.
Purpose of the Study:
- To develop a single-molecule fluorescence system for real-time visualization of full-length p53 tetramer binding to DNA.
- To investigate the dynamics of p53/DNA complex assembly and disassembly.
- To determine how DNA response element structure influences p53/DNA complex stability and kinetics.
Main Methods:
- Utilized a single-molecule fluorescence system to observe full-length p53 tetramers interacting with DNA in real time.
- Analyzed the assembly and disassembly kinetics of p53/DNA complexes.
- Investigated p53 binding to wild-type response elements, single half-sites, and altered DNA structures.
Main Results:
- Observed dynamic assembly and disassembly of p53/DNA complexes without a dimer/DNA intermediate.
- Identified two kinetically distinct populations of p53/DNA complexes on wild-type DNA with two half-sites.
- Found that p53 tetramers binding to single half-sites formed less stable complexes.
- Demonstrated that DNA spacing and phasing between half-sites modulate complex population distribution and stability.
Conclusions:
- Real-time single-molecule measurements provide new insights into p53/DNA interactions.
- The study elucidates key parameters governing p53/DNA complex stability.
- Findings offer a deeper understanding of the assembly pathways for p53 transcription factor complexes.
Related Concept Videos
02:04Covalently Linked Protein Regulators
These groups modify specific amino acids in a protein....
00:49Ligand Binding and Linkage