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ei24, a p53 response gene involved in growth suppression and apoptosis
Z Gu1, C Flemington, T Chittenden
1Department of Biochemistry, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, USA.
Abstract:
DNA damage and/or hyperproliferative signals activate the wild-type p53 tumor suppressor protein, which induces a G(1) cell cycle arrest or apoptosis. Although the mechanism of p53-mediated cell cycle arrest is fairly well defined, the p53-dependent pathway regulating apoptosis is poorly understood. Here we report the functional characterization of murine ei24 (also known as PIG8), a gene directly regulated by p53, whose overexpression negatively controls cell growth and induces apoptotic cell death. Ectopic ei24 expression markedly inhibits cell colony formation, induces the morphological features of apoptosis, and reduces the number of beta-galactosidase-marked cells, which is efficiently blocked by coexpression of Bcl-X(L). The ei24/PIG8 gene is localized on human chromosome 11q23, a region frequently altered in human cancers. These results suggest that ei24 may play an important role in negative cell growth control by functioning as an apoptotic effector of p53 tumor suppressor activities.
Insights
The study identifies ei24 as a p53-regulated gene that induces apoptosis and inhibits cell growth. Overexpression of ei24 promotes cell death, suggesting its role as a tumor suppressor.
Area of Science:
- Molecular Biology
- Cancer Biology
- Cell Death Pathways
Background:
- The wild-type p53 tumor suppressor protein regulates cell cycle arrest and apoptosis in response to DNA damage or hyperproliferative signals.
- While p53-mediated cell cycle arrest mechanisms are understood, the p53-dependent apoptotic pathway remains unclear.
Purpose of the Study:
- To functionally characterize the murine ei24 gene (also known as PIG8), a novel p53 target gene.
- To investigate the role of ei24 in p53-mediated apoptosis and cell growth control.
Main Methods:
- Functional characterization of murine ei24 gene expression and its effects on cell behavior.
- Ectopic expression of ei24 in cells to assess its impact on cell proliferation and apoptosis.
- Investigating the interaction with Bcl-X(L) to understand the apoptotic pathway.
Main Results:
- Murine ei24 is directly regulated by p53 and its overexpression inhibits cell colony formation.
- Ectopic ei24 expression induces morphological features of apoptosis and reduces viable cell numbers.
- The apoptotic effect of ei24 is blocked by coexpression of Bcl-X(L), indicating its involvement in the apoptotic pathway.
- The ei24/PIG8 gene is located on human chromosome 11q23, a region frequently altered in cancers.
Conclusions:
- Ei24 functions as an apoptotic effector of p53 tumor suppressor activity.
- Ei24 plays a significant role in negative cell growth control.
- The localization of ei24 on chromosome 11q23 suggests its potential involvement in human tumorigenesis.