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High expression of ras p21 correlates with increased rate of abnormal mitosis in NIH3T3 cells
N Hagag1, L Diamond, R Palermo
1Division of Oncology, State University of New York, Stony Brook 11794.
Abstract:
The modulation of responsive genes by hormonal stimulation is an attractive in vitro model system for the study of a wide variety of biological processes. Using this methodology we have investigated the effect of the human oncogene protein p21ras on mitosis using mouse mammary tumor virus long terminal repeat (MMTV-LTR)-directed gene expression. Following the induction of p21 protein, abnormal mitotic figures were scored in metaphase and anaphase. Elevated expression of p21 was associated with marked increase in the proportion of abnormal mitoses most significantly during the metaphase. Concomitant with a three fold increase in p21 levels, abnormal mitosis rose from 14.0% to 27.25%. The increase in abnormal mitosis corresponded to a 225% increase in abnormal metaphase. The p21-induced mitotic abnormalities were exhibited as lagging chromosomes in prometaphase, 3 group metaphase and C-metaphase. In addition, high expression of p21 was accompanied by significant changes in the cell morphology and fine ultrastructure, e.g. disorganization of actin, the extensive formation of microvilli on the plasma membrane and marked dilatation of the rough endoplasmic reticulum. The mitotic and structural changes were reversible upon removal of dexamethasone and decline of p21 production to its basal levels. Our results identify an important biological effect of ras p21 during mitosis and the early stages of neoplastic transformation.
Insights
The human oncogene protein p21ras significantly increases abnormal mitosis, particularly during metaphase, and alters cell structure. These effects are reversible, suggesting ras p21
Area of Science:
- Molecular Biology
- Cell Biology
- Oncology
Background:
- Hormonal stimulation modulates gene expression, providing a model for studying biological processes.
- The human oncogene protein p21ras plays a role in cell growth and differentiation.
Purpose of the Study:
- To investigate the effect of p21ras on mitosis using a mouse mammary tumor virus long terminal repeat (MMTV-LTR)-directed gene expression system.
- To analyze the impact of elevated p21ras on mitotic abnormalities and cellular ultrastructure.
Main Methods:
- Utilized MMTV-LTR-directed gene expression to induce p21ras.
- Scored abnormal mitotic figures in metaphase and anaphase.
- Examined changes in cell morphology and fine ultrastructure.
Main Results:
- Elevated p21ras expression significantly increased abnormal mitoses, especially in metaphase (from 14.0% to 27.25%).
- Observed specific mitotic abnormalities including lagging chromosomes and C-metaphase.
- Noted significant alterations in cell morphology, actin organization, and endoplasmic reticulum structure.
Conclusions:
- Ras p21 has a significant biological effect on mitosis, inducing abnormalities.
- The observed changes in mitosis and cell structure are reversible upon p21ras decline.
- These findings contribute to understanding ras p21's role in mitosis and early neoplastic transformation.