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Cell growth-regulated expression of mammalian MCM5 and MCM6 genes mediated by the transcription factor E2F
K Ohtani1, R Iwanaga, M Nakamura
1Human Gene Sciences Center, Tokyo Medical and Dental University, Japan.
Abstract:
Initiation of DNA replication requires the function of MCM gene products, which participate in ensuring that DNA replication occurs only once in the cell cycle. Expression of all mammalian genes of the MCM family is induced by growth stimulation, unlike yeast, and the mRNA levels peak at G1/S boundary. In this study, we examined the transcriptional activities of isolated human MCM gene promoters. Human MCM5 and MCM6 promoters with mutation in the E2F sites failed in promoter regulation following serum stimulation and exogenous E2F expression. In addition, we identified a novel E2F-like sequence in human MCM6 promoter which cooperates with the authentic E2F sites in E2F-dependent regulation. Forced expression of E2F1 could induce expression of all members of the endogenous MCM genes in rat embryonal fibroblast REF52 cells. Our results demonstrated that the growth-regulated expression of mammalian MCM5 and MCM6 genes, and presumably other MCM members, is primarily regulated by E2F through binding to multiple E2F sites in the promoters.
Insights
Mammalian MCM gene expression, crucial for DNA replication control, is regulated by E2F transcription factors. This study shows E2F binding to MCM promoters drives growth-regulated gene expression, ensuring replication occurs once per cell cycle.
Area of Science:
- Molecular Biology
- Cell Cycle Regulation
- Genetics
Background:
- DNA replication initiation relies on MCM (minichromosome maintenance) gene products.
- Mammalian MCM gene expression is growth-stimulated, peaking at the G1/S phase boundary, unlike in yeast.
- Understanding the transcriptional regulation of MCM genes is vital for cell cycle control.
Purpose of the Study:
- To investigate the transcriptional regulation of human MCM gene promoters.
- To determine the role of E2F transcription factors in the growth-regulated expression of MCM genes.
Main Methods:
- Analysis of isolated human MCM5 and MCM6 gene promoters.
- Site-directed mutagenesis of E2F binding sites within promoters.
- Assessment of promoter activity following serum stimulation and exogenous E2F expression.
- Examination of endogenous MCM gene expression in response to E2F1 overexpression.
Main Results:
- Mutating E2F sites in MCM5 and MCM6 promoters abolished regulation by serum stimulation and E2F.
- A novel E2F-like sequence in the MCM6 promoter was identified, cooperating with existing E2F sites.
- Overexpression of E2F1 induced expression of all endogenous MCM genes in REF52 cells.
Conclusions:
- Mammalian MCM gene expression, including MCM5 and MCM6, is primarily controlled by E2F transcription factors.
- E2F regulates MCM genes through binding to multiple E2F sites within their promoters.
- This E2F-mediated regulation ensures proper cell cycle progression and DNA replication control.