In vitro transforming capacities of mouse c-jun:junD chimeric genes
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Updated: Jun 19, 2026
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Published on: November 29, 2012
1Laboratoire de Biologie Moléculaire et Cellulaire, Ecole Normale Supérieure, CNRS-UMR49, Lyon, France.
Abstract:
Among the murine Jun family of transcription factors, c-Jun and JunD are closely-related proteins with similar dimerization, DNA binding and transactivating properties. However, when expressed from a self-replicating retroviral RCAS vector, c-jun, but not junD, transforms chick embryo fibroblasts. We attempted to map the regions of c-jun which are important for transformation by constructing hybrids between c-jun and junD. Using common restriction sites, we prepared six different chimeric molecules. All of these c-jun:junD hybrids code for transactivators of AP1-containing promoters. An N-terminal segment of 79 amino acids of c-Jun converts JunD into a strong transforming protein, while other segments of c-Jun contribute to a lesser extent. Contrary to what has been reported with rat embryo fibroblasts, a c-Jun derivative with serines substituted by alanines in positions 63 and 73 still transforms CEFs efficiently.
Insights
The N-terminal region of c-Jun is crucial for transforming chick embryo fibroblasts, converting JunD into a potent transforming protein. This finding highlights specific domains responsible for oncogenic activity in Jun family transcription factors.
Area of Science:
- Molecular Biology
- Oncogenesis
- Transcription Factors
Background:
- c-Jun and JunD are related murine transcription factors with similar DNA binding and transactivation properties.
- While c-Jun transforms chick embryo fibroblasts (CEFs) via retroviral vectors, JunD does not, suggesting distinct functional domains.
Purpose of the Study:
- To identify the specific regions of c-Jun responsible for its transforming activity.
- To understand the structure-function relationship between c-Jun and JunD in cellular transformation.
Main Methods:
- Construction of six c-Jun:JunD chimeric hybrid molecules using common restriction sites.
- Expression of these hybrids in chick embryo fibroblasts using a self-replicating RCAS vector.
- Assessment of the transforming potential and AP1 transactivation activity of the chimeric proteins.
Main Results:
- All c-Jun:JunD hybrids retained the ability to transactivate AP1-containing promoters.
- An N-terminal segment of 79 amino acids from c-Jun was sufficient to confer strong transforming activity to JunD.
- Other c-Jun segments contributed to a lesser extent to the transforming potential.
- A c-Jun derivative with serine to alanine substitutions at positions 63 and 73 efficiently transformed CEFs, contrasting with previous findings in rat embryo fibroblasts.
Conclusions:
- The N-terminal domain of c-Jun plays a critical role in cellular transformation.
- Specific amino acid residues (Ser63 and Ser73) are not essential for c-Jun-mediated transformation of CEFs.
- Domain mapping of Jun family proteins provides insights into their oncogenic mechanisms.
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