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A novel E2 box-GATA element modulates Cdc6 transcription during human cells polyploidization.
Nuria Vilaboa1, Rodrigo Bermejo, Pilar Martinez
1Department of Biochemistry, Instituto de Investigaciones Biomédicas A. Sols, Universidad Autónoma-CSIC, Arturo Duperier, 4, 28029 Madrid, Spain.
Nucleic Acids Research
|December 14, 2004
Summary
Cell division cycle 6 (Cdc6) expression is upregulated during megakaryocytic differentiation. Transcriptional repressor Escargot inhibits this activation by binding a novel cis-regulatory element, revealing key mechanisms of Cdc6 regulation.
Area of Science:
- Cell Biology
- Molecular Biology
- Gene Regulation
Background:
- Cdc6 is crucial for cell cycle regulation, ensuring proper S and M phase alternation.
- Polyploidization in mammalian and plant cells involves complex transcriptional and post-translational regulation of Cdc6.
- Previous work showed Cdc6 downregulation by Escargot in HEL cells.
Purpose of the Study:
- To investigate the regulation of cdc6 promoter activity during megakaryocytic differentiation.
- To elucidate the role of Escargot in modulating cdc6 expression in endoreplicating cells.
- To identify cis-regulatory elements and transcription factors involved in cdc6 transcriptional control.
Main Methods:
- Analysis of cdc6 promoter activity in HEL endoreplicating cells.
- Transactivation experiments to identify enhancer regions.
- In vitro binding assays for Escargot and regulatory elements.
- Chromatin Immunoprecipitation (ChIP) to assess in vivo transcription factor binding.
Main Results:
- cdc6 promoter activity is upregulated during megakaryocytic differentiation.
- A 1.7 kb upstream region acts as an enhancer specifically in endoreplicating cells.
- This enhancer activity depends on a novel E2 box overlapping a GATA motif.
- Escargot binds this regulatory element, and GATA-1/E2A complexes form and bind the site in vivo.
Conclusions:
- cdc6 expression is actively maintained during megakaryocytic differentiation via transcriptional mechanisms.
- Specific cis-regulatory elements (E2 box/GATA motif) and trans-acting factors (Escargot, GATA-1, E2A) mediate this regulation.
- Escargot's interference with enhancer activity provides insight into controlling Cdc6 levels.