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The role of p53 in cell cycle regulation
1Division of Experimental Oncology, Institute of Pathology, Lausanne, Switzerland.
Abstract:
The tumor suppressor gene p53, implicated in diverse types of human tumors, functions both as a gene-specific transcription factor as well as a specific inhibitor of the transcription of certain genes. The two physiological outcomes of re-expression of wild type p53 in tumor cells, not expressing wild type p53, are G1 arrest and apoptosis. The mechanism of G1 arrest by p53 is much better documented than its ability to trigger apoptosis. P53 as a transcription factor induces the expression of p21WAF1/CIP1/Sdi1, an inhibitor of the cyclin dependent kinases (CDKs)2, 3, 4 and 6. Thus, a G1 arrest can result simply by the p53 induced expression of p21WAF1/CIP1/Sdi1. Amongst the other genes presently characterized to be regulated by p53 are BAX, a homologue of the BCL-2 gene. Bax does not trigger apoptosis, but simply accelerates the rate at which apoptosis proceeds54. P53 also down regulates the expression of cyclin A, providing a secondary break on cell cycle progression into the through the S phase.
Insights
The tumor suppressor gene p53 halts cancer cell growth by inducing G1 arrest and apoptosis. It achieves this by regulating key cell cycle genes like p21WAF1/CIP1/Sdi1 and BAX.
Area of Science:
- Molecular Biology
- Cancer Biology
- Genetics
Background:
- The p53 gene is a crucial tumor suppressor involved in various human cancers.
- Its functions include gene-specific transcription and inhibition of specific gene transcription.
- Re-expression of wild-type p53 in tumor cells can lead to G1 arrest and apoptosis.
Purpose of the Study:
- To elucidate the mechanisms by which p53 induces G1 arrest and apoptosis.
- To identify specific genes regulated by p53 that contribute to these outcomes.
Main Methods:
- Analysis of p53's role as a transcription factor.
- Investigation of p53's regulation of cell cycle inhibitors and apoptosis-related genes.
Main Results:
- p53 induces G1 arrest through the upregulation of p21WAF1/CIP1/Sdi1, a cyclin-dependent kinase (CDK) inhibitor.
- p53 regulates BAX, a gene that accelerates apoptosis.
- p53 downregulates cyclin A, further inhibiting cell cycle progression into the S phase.
Conclusions:
- p53 plays a significant role in cell cycle control and programmed cell death.
- The p53-mediated induction of p21WAF1/CIP1/Sdi1 is a primary mechanism for G1 arrest.
- p53 influences apoptosis through the regulation of genes like BAX and cyclin A.