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A novel transcriptional repression domain mediates p21(WAF1/CIP1) induction of p300 transactivation
A W Snowden1, L A Anderson, G A Webster
1Division of Gene Regulation and Expression, Department of Biochemistry, University of Dundee, Dundee DD1 5EH, Scotland, United Kingdom.
Abstract:
The transcriptional coactivators p300 and CREB binding protein (CBP) are important regulators of the cell cycle, differentiation, and tumorigenesis. Both p300 and CBP are targeted by viral oncoproteins, are mutated in certain forms of cancer, are phosphorylated in a cell cycle-dependent manner, interact with transcription factors such as p53 and E2F, and can be found complexed with cyclinE-Cdk2 in vivo. Moreover, p300-deficient cells show defects in proliferation. Here we demonstrate that transcriptional activation by both p300 and CBP is stimulated by coexpression of the cyclin-dependent kinase inhibitor p21(WAF/CIP1). Significantly this stimulation is independent of both the inherent histone acetyltransferase (HAT) activity of p300 and CBP and of the previously reported carboxyl-terminal binding site for cyclinE-Cdk2. Rather, we describe a previously uncharacterized transcriptional repression domain (CRD1) within p300. p300 transactivation is stimulated through derepression of CRD1 by p21. Significantly p21 regulation of CRD1 is dependent on the nature of the core promoter. We suggest that CRD1 provides a novel mechanism through which p300 and CBP can switch activities between the promoters of genes that stimulate growth and those that enhance cell cycle arrest.
Insights
The cell cycle regulator p21(WAF/CIP1) enhances the activity of transcriptional coactivators p300 and CREB binding protein (CBP). This occurs via a novel repression domain (CRD1), independent of histone acetyltransferase activity.
Area of Science:
- Molecular Biology
- Cell Biology
- Cancer Research
Background:
- p300 and CREB binding protein (CBP) are crucial transcriptional coactivators regulating cell cycle, differentiation, and tumorigenesis.
- These proteins are implicated in cancer, targeted by viral oncoproteins, and interact with key factors like p53 and E2F.
- p300 dysfunction leads to cellular proliferation defects.
Purpose of the Study:
- To investigate the mechanism by which p21(WAF/CIP1) influences the transcriptional activity of p300 and CBP.
- To identify novel regulatory domains and interactions involved in p300/CBP function.
Main Methods:
- Coexpression of p21(WAF/CIP1) with p300 and CBP.
- Assays to measure transcriptional activation.
- Analysis of histone acetyltransferase (HAT) activity.
- Characterization of a novel transcriptional repression domain (CRD1).
Main Results:
- p21(WAF/CIP1) significantly stimulates transcriptional activation by p300 and CBP.
- This stimulation is independent of the intrinsic HAT activity and the cyclinE-Cdk2 binding site of p300/CBP.
- A previously uncharacterized transcriptional repression domain (CRD1) in p300 was identified.
- p21 enhances p300 activity by relieving repression mediated by CRD1.
- The regulation of CRD1 by p21 is promoter-dependent.
Conclusions:
- p21(WAF/CIP1) acts as a novel regulator of p300 and CBP activity through the CRD1 domain.
- This mechanism provides a new way for p300/CBP to modulate gene expression, switching between growth promotion and cell cycle arrest.
- The findings offer insights into the complex regulation of cell growth and cancer development.