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Functional antagonism between YY1 and the serum response factor
A Gualberto1, D LePage, G Pons
1Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106.
Abstract:
The rapid, transient induction of the c-fos proto-oncogene by serum growth factors is mediated by the serum response element (SRE). The SRE shares homology with the muscle regulatory element (MRE) of the skeletal alpha-actin promoter. It is not known how these elements respond to proliferative and cell-type-specific signals, but the response appears to involve the binding of the serum response factor (SRF) and other proteins. Here, we report that YY1, a multifunctional transcription factor, binds to SRE and MRE sequences in vitro. The methylation interference footprint of YY1 overlaps with that of the SRF, and YY1 competes with the SRF for binding to these DNA elements. Overexpression of YY1 repressed serum-inducible and basal expression from the c-fos promoter and repressed basal expression from the skeletal alpha-actin promoter. YY1 also repressed expression from the individual SRE and MRE sequences upstream from a TATA element. Unlike that of YY1, SRF overexpression alone did not influence the transcriptional activity of the target sequence, but SRF overexpression could reverse YY1-mediated trans repression. These data suggest that YY1 and the SRF have antagonistic functions in vivo.
Insights
The transcription factor YY1 binds to DNA elements regulating gene expression, including the serum response element (SRE) and muscle regulatory element (MRE). YY1 antagonizes the serum response factor (SRF), impacting gene activation.
Area of Science:
- Molecular Biology
- Gene Regulation
- Transcription Factors
Background:
- The c-fos proto-oncogene's induction by growth factors involves the serum response element (SRE).
- The SRE shares homology with the muscle regulatory element (MRE) in the alpha-actin promoter.
- The roles of SRE and MRE in responding to proliferative and cell-type-specific signals, involving serum response factor (SRF) binding, are not fully understood.
Purpose of the Study:
- To investigate the binding of the transcription factor YY1 to SRE and MRE sequences.
- To determine the functional relationship between YY1 and SRF in regulating gene expression.
Main Methods:
- In vitro binding assays to assess YY1 interaction with SRE and MRE.
- Methylation interference footprinting to map YY1 and SRF binding sites.
- Reporter gene assays to evaluate the effects of YY1 and SRF overexpression on promoter activity.
- Analysis of gene expression from c-fos and skeletal alpha-actin promoters.
Main Results:
- YY1 binds to both SRE and MRE sequences in vitro.
- YY1 binding sites overlap with and compete against SRF binding sites.
- Overexpression of YY1 represses basal and serum-inducible expression from c-fos and basal expression from the alpha-actin promoter.
- SRF overexpression reverses YY1-mediated repression, indicating antagonistic functions.
Conclusions:
- YY1 acts as a repressor of both c-fos and skeletal alpha-actin gene expression.
- YY1 and SRF exhibit antagonistic functions in vivo, influencing transcriptional regulation.
- These findings reveal a novel regulatory mechanism involving YY1 and SRF in gene expression control.