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p53 Transcriptional activity is mediated through the SRC1-interacting domain of CBP/p300
Jill A Livengood1, Kirsten E S Scoggin, Karen Van Orden
1Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, Colorado 80523-1870, USA.
Abstract:
The tumor suppressor p53 recruits the cellular coactivator CBP/p300 to mediate the transcriptional activation of target genes. In this study, we identify a novel p53-interacting region in CBP/p300, which we call CR2, located near the carboxyl terminus. The 95-amino acid CR2 region (amino acids 2055--2150) is located adjacent to the C/H3 domain and corresponds precisely with the minimal steroid receptor coactivator 1 (SRC1)-interacting domain of CBP (also called IBiD). We show that the region of p53 that participates in the CR2 interaction resides within the first 107 amino acids of the protein. p53 binds strongly to the CR2 domain of both CBP and the highly homologous coactivator p300. Importantly, an in-frame deletion of CR2 within the full-length p300 protein strongly compromises p300-mediated p53 transcriptional activation from a chromatin template in vitro. The identification of the p53-interacting CR2 domain in CBP/p300 prompted us to ask if the human T-cell leukemia virus (HTLV-I) Tax protein, which also interacts with CR2, competes with p53 for binding to this domain. We show that p53 and Tax exhibit mutually exclusive binding to the CR2 region, possibly contributing to the previously reported Tax repression of p53 function. Together, these studies identify and molecularly characterize a new p53 binding site on CBP/p300 that participates in coactivator-mediated p53 transcription function. The identity of the p53.CR2 interaction indicates that at least three distinct sites on CBP/p300 may participate in mediating p53 transactivation.
Insights
Researchers discovered a new p53 binding site, CR2, on coactivators CBP/p300. This interaction is crucial for p53
Area of Science:
- Molecular Biology
- Gene Regulation
- Cancer Research
Background:
- The tumor suppressor p53 relies on coactivators CBP/p300 for gene activation.
- CBP/p300 are crucial cellular coactivators involved in various cellular processes.
Purpose of the Study:
- To identify and characterize novel interaction regions between p53 and CBP/p300.
- To investigate the functional significance of the p53-CBP/p300 interaction in transcriptional activation.
Main Methods:
- Protein interaction mapping to identify p53 binding sites on CBP/p300.
- In vitro transcription assays using chromatin templates to assess functional impact.
- Competition assays to study the interaction between p53, Tax, and CBP/p300.
Main Results:
- A novel p53-interacting region, CR2, was identified in CBP/p300 (amino acids 2055-2150).
- The CR2 domain is essential for p53-mediated transcriptional activation.
- The HTLV-I Tax protein competes with p53 for binding to the CR2 domain, suggesting a mechanism for Tax-mediated repression of p53 function.
Conclusions:
- A new functional p53 binding site (CR2) on CBP/p300 has been identified and characterized.
- This interaction is critical for p53's role in gene transcription.
- The findings provide insights into the interplay between p53, CBP/p300, and viral proteins like Tax.