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Induction of cyclin E-cdk2 kinase activity, E2F-dependent transcription and cell growth by Myc are genetically
R Beier1, A Bürgin, A Kiermaier
1Institute of Molecular Biology and Tumour Research, Emil-Mannkopff-Strabetae 2, 35033 Marburg, Germany.
Abstract:
The c-myc gene has been implicated in three distinct genetic programs regulating cell proliferation: control of cyclin E-cdk2 kinase activity, E2F-dependent transcription and cell growth. We have now used p27(-/-) fibroblasts to dissect these downstream signalling pathways. In these cells, activation of Myc stimulates transcription of E2F target genes, S-phase entry and cell growth without affecting cyclin E-cdk2 kinase activity. Both cyclin D2 and E2F2, potential direct target genes of Myc, are induced in p27(-/-) MycER cells. Ectopic expression of E2F2, but not of cyclin D2, induces S-phase entry, but, in contrast to Myc, does not stimulate cell growth. Our results show that stimulation of cyclin E-cdk2 kinase, of E2F-dependent transcription and of cell growth by Myc can be genetically separated from each other.
Insights
The c-myc gene regulates cell proliferation via cyclin E-cdk2 activity, E2F transcription, and cell growth. Studies show these pathways can be genetically separated, offering new insights into cancer research.
Area of Science:
- Molecular Biology
- Cell Biology
- Genetics
Background:
- The c-myc gene is crucial for cell proliferation, influencing key regulatory pathways.
- Understanding how c-myc controls these pathways is vital for cancer research.
Purpose of the Study:
- To dissect the downstream signaling pathways regulated by the c-myc gene.
- To investigate the distinct roles of c-myc in cell cycle control, transcription, and cell growth.
Main Methods:
- Utilized p27(-/-) fibroblasts to isolate specific signaling cascades.
- Activated Myc in these cells and analyzed the effects on gene transcription and cell cycle progression.
- Examined the impact of ectopic expression of potential c-myc target genes, cyclin D2 and E2F2.
Main Results:
- Myc activation in p27(-/-) fibroblasts stimulated E2F target gene transcription, S-phase entry, and cell growth independently of cyclin E-cdk2 kinase activity.
- Both cyclin D2 and E2F2 were identified as induced genes in p27(-/-) MycER cells.
- Ectopic E2F2 expression induced S-phase entry but not cell growth, while cyclin D2 had no significant effect on either.
Conclusions:
- The study demonstrates that Myc's control over cyclin E-cdk2 kinase activity, E2F-dependent transcription, and cell growth can be genetically separated.
- These findings highlight distinct mechanisms by which Myc drives cell proliferation.