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Updated: Jun 22, 2026

Studying Proteolysis of Cyclin B at the Single Cell Level in Whole Cell Populations
Published on: September 17, 2012
Post-translational modification and stability of low molecular weight cyclin E
1Department of Experimental Radiation Oncology, University of Texas, MD Anderson Cancer Center, Houston, TX 77030, USA.
Researchers identified that phosphorylation at threonine 395 generates larger low molecular weight cyclin E isoforms. These isoforms remain stable in tumor and non-tumor cells, suggesting implications for cancer development and treatment.
Area of Science:
- Molecular Biology
- Cancer Research
- Biochemistry
Background:
- Previously identified five tumor-specific low molecular weight cyclin E isoforms.
- One isoform originates from an alternate start site; others result from elastase-like enzyme cleavage.
- The origin of the cleaved doublets remained unknown.
Purpose of the Study:
- To elucidate the origin of the low molecular weight cyclin E doublets.
- To investigate the role of phosphorylation in generating these isoforms.
- To assess the stability of cyclin E isoforms in different cell types.
Main Methods:
- Site-directed mutagenesis of cyclin E phosphorylation sites.
- Analysis of protein isoforms using biochemical assays.
- Assessment of protein stability in mammary epithelial and tumor cells.
Main Results:
- Phosphorylation at threonine 395 generates the larger isoform of each doublet.
- Mutational analysis confirmed T395 phosphorylation's role in isoform generation.
- Low molecular weight cyclin E isoforms exhibit stability irrespective of T395 phosphorylation status.
Conclusions:
- Phosphorylation at threonine 395 is key to generating specific low molecular weight cyclin E isoforms.
- The stability of these isoforms in both tumor and non-tumor cells suggests a role in tumorigenesis.
- Understanding cyclin E isoform stability may inform cancer treatment strategies.
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