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Article Dans Une Revue Oncogene Année : 1998

Differential directing of c-Fos and c-Jun proteins to the proteasome in serum-stimulated mouse embryo fibroblasts

Résumé

c-Fos and c-Jun proteins are highly unstable transcription factors that heterodimerize within the AP-1 transcription complex. Their accumulation is transiently induced at the beginning of the G0-to-S phase transition in quiescent cells stimulated for growth. To address the mechanisms responsible for rapid clearance of c-Fos and c-Jun proteins under these experimental conditions, we have used the ts20 mouse embryo fibroblasts which express a thermosensitive mutant of the E1 enzyme of the ubiquitin pathway. The use of cell-permeant protease inhibitors indicates that both proteins are degraded by the proteasome and excludes any major contribution for calpains and lysosomes during the G0-to-S phase transition. Synchronisation of ts20 cells at the non permissive temperature blocks the degradation of c-Jun, indicating that this process is E1-dependent. In contrast, c-Fos is broken down according to an apparently E1-independent pathway in ts20 cells, although a role for ubiquitinylation in this process cannot be formally ruled out. Interestingly, c-Jun is highly unstable in c-Fos-null mouse embryo fibroblasts stimulated for growth. Taken together, these observations show that in vivo during a G0-to-S phase transition (i) the precise mechanisms triggering c-Fos and c-Jun directing to the proteasome are not identical, (ii) the presence of c-Fos is not an absolute prerequisite for the degradation of c-Jun and (iii) the degradation of c-Jun is not required for that of c-Fos.
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Dates et versions

hal-02195936 , version 1 (26-07-2019)

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C. Salvat, I. Jariel-Encontre, C. Acquaviva, S. Omura, Marc Piechaczyk. Differential directing of c-Fos and c-Jun proteins to the proteasome in serum-stimulated mouse embryo fibroblasts. Oncogene, 1998, 17 (3), pp.327--37. ⟨10.1038/sj.onc.1201922⟩. ⟨hal-02195936⟩
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