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Topoisomerase II: its functions and phosphorylation.
1Swiss Institute for Experimental Cancer Research (ISREC), Epalinges s/Lausanne.
Antonie Van Leeuwenhoek
|August 1, 1992
Summary
Topoisomerase II is crucial for cell division in yeast and vertebrates. Casein kinase II (CKII) phosphorylates yeast topoisomerase II, impacting chromosome condensation.
Area of Science:
- Molecular Biology
- Cell Biology
- Genetics
Background:
- Topoisomerase II (Topo II) is essential for yeast mitotic and meiotic proliferation.
- Studies show Topo II's roles in managing torsional stress, recombination, and sister chromatid separation.
- Topo II is a key component of vertebrate metaphase chromosomal scaffolds, involved in chromosome condensation.
Purpose of the Study:
- To investigate the role of Topoisomerase II phosphorylation in cell cycle control.
- To identify the enzyme responsible for phosphorylating Topoisomerase II in yeast.
- To determine the specific regions of Topoisomerase II targeted by this phosphorylation.
Main Methods:
- Utilized temperature-sensitive mutants of yeast Topoisomerase II.
- Analyzed Topoisomerase II phosphorylation levels across different cell cycle phases (G1 vs. metaphase).
- Identified the phosphorylating enzyme using biochemical assays in yeast cells.
Main Results:
- Topoisomerase II is more highly phosphorylated in metaphase than in G1 phase.
- Casein kinase II (CKII) was identified as the primary enzyme phosphorylating Topoisomerase II in yeast.
- CKII targets the C-terminal 400 amino acids of Topoisomerase II, a divergent region among eukaryotes.
Conclusions:
- Phosphorylation of Topoisomerase II by CKII likely plays a role in cell cycle-controlled chromosome condensation.
- The C-terminal region of Topoisomerase II is critical for its regulation and function.
- Understanding Topo II regulation offers insights into eukaryotic chromosome dynamics.