High impact information on top3

• In Schizosaccharomyces pombe, topoisomerase III is encoded by a single gene, top3(+), which is essential for cell viability and proper chromosome segregation [1].
• Using a top3 shut-off strain, we show here that depletion of Top3 activates the DNA damage checkpoint associated with phosphorylation of the checkpoint kinase Chk1 [1].
• Here, we provide evidence suggesting that the lethality in top3 mutants is due to accumulation of aberrant DNA structures that arise during S phase, as judged by pulsed-field gel electrophoresis [1].
• The deletion of the top3(+) gene leads to defective nuclear division and lethality in Schizosaccharo myces pombe [2].
• We generated top3 temperature-sensitive (top3-ts) mutants and found these to be defective in nuclear division and cytokinesis and to be sensitive to DNA-damaging agents [2].

Biological context of top3

• Despite activation of this checkpoint, top3 cells exit the arrest but fail to undergo faithful chromosome segregation [1].
• Fission yeast haploid spores containing a disrupted top3 (+)gene germinate successfully, but then undergo only a limited number of cell divisions [3].

References