Novel splice variants of cyclin E with altered substrate specificity.

Area of Science:

• Molecular Biology
• Cancer Research
• Cell Cycle Regulation

Background:

• Cyclin E is a G(1) cyclin implicated in cell cycle progression.
• Overexpression and low molecular weight (LMW) isoforms of Cyclin E are observed in breast cancer.
• The origin of these tumor-specific LMW Cyclin E proteins remains unclear.

Purpose of the Study:

• To investigate if shortened mRNA splice variants of Cyclin E could produce tumor-specific LMW proteins.
• To identify and characterize novel Cyclin E mRNA splice variants in cancer cells.

Main Methods:

• Utilized the Splice Capture method to identify, enumerate, and isolate Cyclin E mRNA splice variants.
• Compared Splice Capture to the conventional RNase protection assay for analyzing Cyclin E mRNA.
• Assayed the activity of a novel splice variant (Delta48) on CDK2 and GST-Rb.

Main Results:

• Identified a new Cyclin E splice variant, Delta48, in tumor cells using Splice Capture.
• Delta48 activates CDK2 more robustly than full-length Cyclin E.
• The Splice Capture method proved superior to RNase protection assay for Cyclin E mRNA analysis.
• Discovered and enumerated known and novel Cyclin E splice variants in normal and tumor cells.

Conclusions:

• The abundance of Cyclin E splice variants may represent a novel regulatory mechanism for Cyclin E.
• The Delta48 splice variant exhibits altered substrate specificity compared to full-length Cyclin E.
• Splice variants, if translated, can lead to functionally distinct Cyclin E proteins in cancer.