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Deletion of Mnt leads to disrupted cell cycle control and tumorigenesis
Peter J Hurlin1, Zi-Qiang Zhou, Kazuhito Toyo-oka
1Shriners Hospitals for Children, Department of Cell and Developmental Biology, Oregon Health Sciences University, Portland, OR, USA. pjh@shcc.org
Abstract:
Mnt is a Max-interacting transcriptional repressor that has been hypothesized to function as a Myc antagonist. To investigate Mnt function we deleted the Mnt gene in mice. Since mice lacking Mnt were born severely runted and typically died within several days of birth, mouse embryo fibroblasts (MEFs) derived from these mice and conditional Mnt knockout mice were used in this study. In the absence of Mnt, MEFs prematurely entered the S phase of the cell cycle and proliferated more rapidly than Mnt(+/+) MEFs. Defective cell cycle control in the absence of Mnt is linked to upregulation of Cdk4 and cyclin E and the Cdk4 gene appears to be a direct target of Mnt-Myc antagonism. Like MEFs that overexpress Myc, Mnt(-/-) MEFs were prone to apoptosis, efficiently escaped senescence and could be transformed with oncogenic Ras alone. Consistent with Mnt functioning as a tumor suppressor, conditional inactivation of Mnt in breast epithelium led to adenocarinomas. These results demonstrate a unique negative regulatory role for Mnt in governing key Myc functions associated with cell proliferation and tumorigenesis.
Insights
Mnt protein acts as a tumor suppressor by inhibiting Myc, a key driver of cell proliferation and cancer. Its absence leads to rapid cell growth and tumor formation.
Area of Science:
- Molecular Biology
- Cancer Research
- Genetics
Background:
- Mnt (Max-interacting transcriptional repressor) is a hypothesized Myc antagonist.
- Myc is a critical regulator of cell proliferation and tumorigenesis.
Purpose of the Study:
- To investigate the function of Mnt as a Myc antagonist and tumor suppressor.
- To elucidate the role of Mnt in cell cycle control and oncogenesis.
Main Methods:
- Gene deletion of Mnt in mice.
- Analysis of Mnt-deficient mouse embryo fibroblasts (MEFs).
- Conditional Mnt knockout in mouse breast epithelium.
Main Results:
- Mnt deficiency leads to premature S phase entry and rapid proliferation in MEFs.
- Absence of Mnt results in upregulation of Cdk4 and cyclin E, with Cdk4 as a direct Mnt-Myc target.
- Mnt(-/-) MEFs exhibit increased apoptosis, escape senescence, and transform readily with oncogenic Ras.
- Conditional Mnt inactivation in breast tissue causes adenocarcinoma formation.
Conclusions:
- Mnt functions as a tumor suppressor by negatively regulating Myc-driven cell proliferation.
- Mnt plays a critical role in preventing uncontrolled cell growth and tumorigenesis.