Related Experiment Videos
Collaborative competition mechanism for gene activation in vivo
Joanna A Miller1, Jonathan Widom
1Department of Biochemistry, Molecular Biology and Cellular Biology, Northwestern University, Evanston, Illinois 60208-3500, USA.
Molecular and Cellular Biology
|February 18, 2003
Summary
Gene regulatory proteins use collaborative competition to access DNA sites within nucleosomes. This mechanism, involving proteins like LexA and Tet repressor, enhances gene activation in yeast by overcoming chromatin barriers.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- The mechanism of gene regulatory protein access to DNA target sites remains unclear.
- In vitro studies suggest cooperative binding between DNA-binding proteins on the same nucleosome, termed collaborative competition.
Purpose of the Study:
- To investigate the in vivo role of collaborative competition in gene regulation.
- To determine if foreign DNA-binding proteins can cooperate with endogenous activators in Saccharomyces cerevisiae.
Main Methods:
- Utilized LexA and Tet repressor as foreign DNA-binding proteins.
- Co-expressed these proteins with an endogenous activator (Gcn4) in yeast.
- Measured coactivation of chromosomal reporter genes and analyzed protein occupancy.
Main Results:
- Demonstrated that LexA and Tet repressor coactivate gene expression with Gcn4 in yeast.
- Coactivation is dependent on target site proximity within a nucleosome.
- Observed increased Gcn4 binding and requirement for Gcn5 and Swi/Snf chromatin remodelers.
Conclusions:
- Collaborative competition contributes to gene regulation in vivo.
- Competition with histone octamers is a key factor in gene expression levels, even with chromatin remodelers present.
- Suggests initial DNA binding may involve spontaneous nucleosomal site exposure, with remodeling factors stabilizing occupancy.