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Cell-cycle-specific interaction of nuclear DNA-binding proteins with a CCAAT sequence from the human thymidine kinase
G B Knight1, J M Gudas, A B Pardee
1Department of Pharmacology, Harvard Medical School, Boston, MA.
Abstract:
Induction of thymidine kinase parallels the onset of DNA synthesis. To investigate the transcriptional regulation of the thymidine kinase gene, we have examined whether specific nuclear factors interact in a cell-cycle-dependent manner with sequences upstream of this gene. Two inverted CCAAT boxes near the transcriptional initiation sites were observed to form complexes with nuclear DNA-binding proteins. The nature of the complexes changes dramatically as the cells approach DNA synthesis and correlates well with the previously reported transcriptional increase of the thymidine kinase gene.
Insights
Nuclear factors binding to the thymidine kinase gene change during the cell cycle. These changes correlate with increased thymidine kinase gene activity, crucial for DNA synthesis.
Area of Science:
- Molecular Biology
- Cell Cycle Regulation
- Gene Expression
Background:
- Thymidine kinase (TK) gene expression increases with DNA synthesis.
- Understanding the transcriptional regulation of TK is key to understanding cell proliferation.
Purpose of the Study:
- To investigate the cell-cycle-dependent transcriptional regulation of the thymidine kinase gene.
- To identify nuclear factors interacting with upstream sequences of the TK gene.
Main Methods:
- Analysis of nuclear factor interactions with DNA sequences upstream of the thymidine kinase gene.
- Examination of protein-DNA complex formation during different cell cycle phases.
Main Results:
- Specific nuclear factors bind to two inverted CCAAT boxes upstream of the TK gene.
- The composition of these protein-DNA complexes changes significantly as cells enter DNA synthesis.
- These alterations in DNA-binding proteins correlate with the induction of TK gene transcription.
Conclusions:
- Transcriptional regulation of the thymidine kinase gene involves cell-cycle-dependent interactions with specific nuclear factors.
- CCAAT boxes are critical regulatory elements for TK gene expression during the cell cycle.