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The carboxy terminus of the viral Jun oncoprotein is required for complex formation with the cellular Fos protein
T J Bos1, F J Rauscher, T Curran
1Department of Microbiology, University of Southern California School of Medicine, Los Angeles 90033-1054.
Abstract:
The products of the proto-oncogenes c-jun and c-fos are known to form a complex in vivo. Complex formation appears to stabilize protein-DNA interactions and is thought to play an important functional role in transcriptional regulation. Here we show that the viral Jun oncoprotein, which differs structurally from cellular Jun, is also capable of complex formation with Fos. Thus the oncogenic potency of viral Jun is unlikely to be due to an altered affinity for Fos. We have also defined, by deletion analysis, the domain of v-Jun responsible for complex formation to reside in the carboxy terminus encompassing the leucine zipper motif. We find that complex formation with c-Fos does not occur with v-Jun deletions affecting one or more leucine residues in the zipper domain. Our results are consistent with the hypothesis that the leucine zipper mediates Jun-Fos interaction.
Insights
Viral Jun oncoprotein forms complexes with Fos, similar to cellular Jun. The leucine zipper domain in v-Jun is crucial for this interaction, suggesting it mediates Jun-Fos binding.
Area of Science:
- Molecular Biology
- Oncogenesis
- Protein-protein interactions
Background:
- Proto-oncogenes c-jun and c-fos encode proteins that form complexes.
- Complex formation stabilizes protein-DNA interactions and regulates transcription.
- Viral Jun oncoprotein (v-Jun) differs structurally from cellular Jun (c-Jun).
Purpose of the Study:
- To investigate the complex formation between v-Jun and cellular Fos (c-Fos).
- To determine if v-Jun's oncogenic potential is due to altered Fos binding affinity.
- To identify the domain within v-Jun responsible for complex formation with c-Fos.
Main Methods:
- Deletion analysis of the v-Jun protein.
- Assessment of complex formation between wild-type and mutant v-Jun with c-Fos.
Main Results:
- v-Jun forms complexes with c-Fos, similar to c-Jun.
- The carboxy-terminal region of v-Jun, including the leucine zipper motif, is essential for complex formation.
- Deletions in the v-Jun leucine zipper domain abolish c-Fos binding.
Conclusions:
- The oncogenic potency of v-Jun is unlikely to stem from altered Fos-binding affinity.
- The leucine zipper domain mediates the interaction between Jun and Fos proteins.
- This interaction is critical for the functional role of Jun-Fos complexes in transcriptional regulation.