Related Experiment Videos
Nuclear localization of cyclin B1 regulates DNA damage-induced apoptosis
Lisa A Porter1, I Howard Cukier, Jonathan M Lee
1Hamilton Regional Cancer Center, Hamilton, ON, Canada.
Abstract:
Some cells undergo apoptosis in response to DNA damage, whereas others do not. To understand the biochemical pathways controlling this differential response, we have studied the intracellular localization of cyclin B1 in cell types sensitive or resistant to apoptosis induced by DNA damage. We found that cyclin B1 protein accumulates in the nucleus of cells that are sensitive to gamma radiation-induced apoptosis (thymocytes, lymphoid cell lines), but remains cytoplasmic in apoptosis-resistant cells (primary and transformed fibroblasts). Treatment of both cell types with leptomycin B, an inhibitor of CRM1-dependent cyclin B1 nuclear export, induces apoptosis. Furthermore, ectopic expression of cyclin B1-5xE, a protein that preferentially localizes to the nucleus, is sufficient to trigger apoptosis. Conversely, expression of cyclin B1-5xA, a predominantly cytoplasmic protein, fails to induce apoptosis. This suggests that nuclear accumulation is necessary for cyclin B1-dependent apoptosis. Our observations are consistent with the idea that localization of cyclin B1 is among the factors determining the cellular decision to undergo apoptosis in response to DNA damage.
Insights
Cellular response to DNA damage varies. Nuclear accumulation of cyclin B1 protein is essential for triggering apoptosis, while cytoplasmic localization prevents it, influencing cell fate decisions.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Cellular responses to DNA damage differ, with some cells undergoing apoptosis and others resisting it.
- Understanding the molecular mechanisms behind this differential apoptosis sensitivity is crucial.
Purpose of the Study:
- To investigate the role of cyclin B1 intracellular localization in differential apoptosis sensitivity following DNA damage.
- To elucidate the biochemical pathways governing cell fate decisions in response to genotoxic stress.
Main Methods:
- Comparative analysis of cyclin B1 protein localization in apoptosis-sensitive and resistant cell types.
- Utilizing leptomycin B to inhibit nuclear export and ectopic expression of cyclin B1 mutants with altered localization.
Main Results:
- Cyclin B1 protein accumulates in the nucleus of apoptosis-sensitive cells (thymocytes, lymphoid lines) but remains cytoplasmic in resistant cells (fibroblasts).
- Inhibition of nuclear export (leptomycin B) or forced nuclear localization of cyclin B1 induces apoptosis.
- Predominantly cytoplasmic cyclin B1 mutants fail to induce apoptosis.
Conclusions:
- Nuclear accumulation of cyclin B1 is a necessary factor for inducing apoptosis in response to DNA damage.
- Intracellular localization of cyclin B1 plays a critical role in determining cellular fate following genotoxic insult.