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Induced expression of human CCND1 alternative transcripts in mouse Cyl-1 knockout fibroblasts highlights functional
Sarah L Holley1, Jim Heighway, Paul R Hoban
1Human Genomics Research Group, Institute for Science and Technology in Medicine, Keele University School of Medicine, University Hospital of North Staffordshire, Stoke-on-Trent, United Kingdom.
International Journal of Cancer
|November 20, 2004
Summary
Human cyclin D1 (CCND1) mRNA splicing produces two transcripts, a and b. CCND1 transcript a promotes cell cycle progression, while CCND1 transcript b enhances anchorage-independent growth, indicating distinct biological functions.
Area of Science:
- Molecular Biology
- Cell Biology
- Cancer Research
Background:
- The human cyclin D1 (CCND1) gene produces two mRNA transcripts, a and b, through alternative splicing.
- A common CCND1 polymorphism (A/G at nucleotide 870) influences splicing and is linked to cancer progression.
- While CCND1 transcript a (CCND1(tra)) has been studied, the function of CCND1 transcript b (CCND1(trb)) remains less understood.
Purpose of the Study:
- To investigate and compare the distinct biological functions of CCND1 transcript a and CCND1 transcript b.
- To analyze the effects of inducible expression of CCND1(tra) and CCND1(trb) in a cyclin D1-deficient mouse fibroblast cell line.
Main Methods:
- Utilized inducible expression systems in mouse embryonic fibroblasts (MEF(Cyl-1-/-)) lacking cyclin D1.
- Isolated stable transfectant clones for CCND1(tra) and CCND1(trb) expression.
- Assessed cell proliferation, DNA synthesis (BrdU incorporation), growth in low serum conditions, and anchorage-independent growth (soft agar colony formation).
Main Results:
- Inducible expression of CCND1(tra) significantly increased S-phase entry and growth in low-serum conditions.
- Inducible expression of CCND1(trb) did not affect DNA synthesis or serum-independent growth.
- CCND1(trb) expression markedly enhanced anchorage-independent growth, with an average 30-fold increase in soft agar colony formation compared to controls and CCND1(tra).
Conclusions:
- CCND1 alternate transcripts encode proteins with distinct biological functions.
- CCND1(tra) is implicated in regulating mitogen-responsive, anchorage-dependent G1 phase progression.
- CCND1(trb) plays a significant role in promoting anchorage-independent cell growth, a hallmark of cancer metastasis.