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Single-cell analysis of lambda immunity regulation.
Kristoffer Baek1, Sine Svenningsen, Harvey Eisen
1Department of Molecular Cell Biology, University of Copenhagen, Øster Farimagsgade 2A, DK-1353, K, Copenhagen, Denmark.
Journal of Molecular Biology
|November 19, 2003
Summary
Bacteriophage lambda repressor (CI) expression fluctuates significantly between individual cells, contrary to prior models. This cellular variability is partially managed by a DNA damage response mechanism.
Area of Science:
- Molecular Biology
- Microbiology
- Genetics
Background:
- The lambda CI operon regulates lysogeny in bacteriophage lambda.
- Previous models of lambda CI operon expression did not account for cell-to-cell variability.
- Understanding gene expression noise is crucial in microbial systems.
Purpose of the Study:
- To investigate the expression patterns of the lambda CI operon at the single-cell level.
- To analyze cell-to-cell fluctuations in repressor concentration.
- To explore the role of DNA damage response in tolerating expression variability.
Main Methods:
- Utilized a reporter system by substituting the lambda CI operon with a 'rex-gfp' construct.
- Quantified fluorescence intensity in single cells to measure repressor expression.
- Analyzed expression data for cell-to-cell heterogeneity.
Main Results:
- Observed significant cell-to-cell fluctuations in repressor concentration, despite average expression aligning with predictions.
- Identified that these fluctuations are not predicted by existing lambda CI operon models.
- Found that a regulatory response to DNA damage helps tolerate these repressor concentration variations.
Conclusions:
- Single-cell analysis reveals substantial heterogeneity in lambda CI repressor expression.
- Cellular variability in repressor levels challenges current theoretical models.
- DNA damage response pathways play a role in mitigating the effects of expression noise.