Measuring cell cycle-dependent DNA damage responses and p53 regulation on a cell-by-cell basis from image analysis
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Updated: Feb 8, 2026
Two- and Three-Dimensional Live Cell Imaging of DNA Damage Response Proteins
Published on: September 28, 2012
Shivnarayan Dhuppar1, Aprotim Mazumder1
1a TIFR Centre for Interdisciplinary Sciences , TIFR Hyderabad , Hyderabad , India.
Abstract:
DNA damage in cells occurs from both endogenous and exogenous sources, and failure to repair such damage is associated with the emergence of different cancers, neurological disorders and aging. DNA damage responses (DDR) in cells are closely associated with the cell cycle. While most of our knowledge of DDR comes from bulk biochemistry, such methods require cells to be arrested at specific stages for cell cycle studies, potentially altering measured responses; nor is cell to cell variability in DDR or direct cell-level correlation of two response metrics measured in such methods. To overcome these limitations we developed a microscopy-based assay for determining cell cycle stages over large cell numbers. This method can be used to study cell-cycle-dependent DDR in cultured cells without the need for cell synchronization. Upon DNA damage γH2A.X induction was correlated to nuclear enrichment of p53 on a cell-by-cell basis and in a cell cycle dependent manner. Imaging-based cell cycle staging was combined with single molecule P53 mRNA detection and immunofluorescence for p53 protein in the very same cells to reveal an intriguing repression of P53 transcript numbers due to reduced transcription across different stages of the cell cycle during DNA damage. Our study hints at an unexplored mechanism for p53 regulation and underscores the importance of measuring single cell level responses to DNA damage.
Insights
This study introduces a microscopy assay to track DNA damage responses (DDR) and cell cycle stages simultaneously. It reveals cell-cycle-dependent p53 regulation during DNA damage, highlighting a novel regulatory mechanism.
Area of Science:
- Molecular Biology
- Cell Biology
- Genetics
Background:
- DNA damage from internal and external sources is linked to cancer, aging, and neurological diseases.
- Cellular DNA damage responses (DDR) are intricately connected to the cell cycle.
- Traditional bulk biochemistry methods for studying DDR require cell synchronization, potentially skewing results and preventing single-cell analysis.
Purpose of the Study:
- To develop a microscopy-based assay for analyzing cell-cycle-dependent DNA damage responses (DDR) in unsynchronized cells.
- To investigate the cell-to-cell variability in DDR and correlate different response metrics at the single-cell level.
- To explore the relationship between DNA damage, cell cycle stage, and p53 regulation.
Main Methods:
- Developed a microscopy assay to determine cell cycle stages in large numbers of cultured cells without synchronization.
- Quantified DNA damage via γH2A.X induction and correlated it with nuclear p53 enrichment on a cell-by-cell basis.
- Combined imaging-based cell cycle staging with single-molecule P53 mRNA detection and p53 protein immunofluorescence in the same cells.
Main Results:
- Established a method to study cell-cycle-dependent DDR without cell synchronization.
- Observed a cell-cycle-dependent correlation between γH2A.X induction and nuclear p53 enrichment.
- Discovered a significant reduction in P53 transcript numbers, attributed to decreased transcription across various cell cycle stages during DNA damage.
Conclusions:
- The study presents a novel microscopy assay for high-throughput, single-cell analysis of DNA damage responses.
- Identified an unexplored mechanism of p53 regulation involving cell-cycle-dependent transcriptional repression during DNA damage.
- Emphasizes the critical importance of assessing single-cell responses to DNA damage for a comprehensive understanding of cellular mechanisms.
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