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The MDM2 RING finger is required for cell cycle-dependent regulation of its protein expression
Ling Gu1, Haoqiang Ying, Hongwu Zheng
1Department of Biochemistry, Boston University School of Medicine, 715 Albany Street, K423, MA 02118, USA.
Abstract:
The MDM2 oncoprotein is overexpressed in many human tumors and cancers. MDM2 functions as an E3 ligase for p53 and for itself. MDM2 also interacts with the retinoblastoma protein (RB) and the transcription factor E2F1 to promote cell cycle S-phase entry. Here, we report that MDM2 protein expression is cell cycle-regulated, which is dependent on its RING finger domain and requires Lys446. We show that MDM2 protein is stabilized at S phase. In addition, overexpression of MDM2 results in stimulation of E2F activity and accumulation of cells in S phase. These data suggest that ubiquitination of MDM2 is cell cycle-regulated and that MDM2 may play a role in cell cycle progression.
Insights
MDM2 oncoprotein regulates cell division and is overexpressed in cancers. This study reveals MDM2 protein levels are controlled by the cell cycle, stabilizing during S phase to promote cell growth.
Area of Science:
- Oncology
- Molecular Biology
- Cell Cycle Regulation
Background:
- The MDM2 oncoprotein is frequently overexpressed in human tumors.
- MDM2 acts as an E3 ligase for p53 and itself, and interacts with RB and E2F1 to drive cell cycle progression.
- Understanding MDM2's role in cell cycle regulation is crucial for cancer therapy.
Purpose of the Study:
- To investigate the cell cycle regulation of MDM2 protein expression.
- To determine the molecular mechanisms underlying MDM2's cell cycle control.
- To elucidate the role of MDM2 in promoting cell cycle S-phase entry.
Main Methods:
- Analysis of MDM2 protein expression levels throughout the cell cycle.
- Investigation of MDM2 ubiquitination and its dependence on the RING finger domain and Lys446.
- Assessment of the impact of MDM2 overexpression on E2F activity and cell cycle distribution.
Main Results:
- MDM2 protein expression is regulated by the cell cycle, requiring its RING finger domain and Lys446.
- MDM2 protein is notably stabilized during the S phase of the cell cycle.
- Overexpression of MDM2 leads to increased E2F activity and accumulation of cells in S phase.
Conclusions:
- MDM2 ubiquitination is a cell cycle-regulated process.
- MDM2 plays a significant role in the progression of the cell cycle, particularly during S phase.
- Targeting MDM2's cell cycle regulatory functions may offer novel therapeutic strategies for cancer.