c-Jun is also phosphorylated at two residues proximal to the major transactivation domain. These residues (Ser 63 and 73) are required to be phosphorylated for efficient transactivation function. The kinases responsible for this modification in vivo are the SAPK/JNKs. These kinases bind with very high affinity to a region in c-Jun termed the delta domain. This region is deleted in v-Jun. v-Jun is not phosphorylated but is transcriptionally active. Thus, binding of inactive SAPK to Jun may represent a mechanism for inhibiting the function of the transcription factor. Once activated, the SAPK will phosphorylate c-Jun and dissociate. Mutation of the phosphorylation sites prevents dissociation thus resulting in inactive c-Jun. v-Jun, on the other hand, cannot bind the kinases and so is constitutively active.
chuckdouble wrote: c-Jun is also phosphorylated at two residues proximal to the major transactivation domain. These residues (Ser 63 and 73) are required to be phosphorylated for efficient transactivation function. The kinases responsible for this modification in vivo are the SAPK/JNKs. These kinases bind with very high affinity to a region in c-Jun termed the delta domain. This region is deleted in v-Jun. v-Jun is not phosphorylated but is transcriptionally active. Thus, binding of inactive SAPK to Jun may represent a mechanism for inhibiting the function of the transcription factor. Once activated, the SAPK will phosphorylate c-Jun and dissociate. Mutation of the phosphorylation sites prevents dissociation thus resulting in inactive c-Jun. v-Jun, on the other hand, cannot bind the kinases and so is constitutively active.