Functional antagonism between c-Jun and MyoD proteins: A direct physical association

c-Jun, at the crossroad of the signaling network

“…Third, the AP-1 proteins can interact with proteins outside the family, resulting in complexes with unique DNA binding and transcription activity. Examples for this type of interaction include c-Jun binding to the Ets domain of PU.1, directing the complex to the PU.1 binding site in the M-CSF receptor promoter for transcriptional activation (Behre et al, 1999), whereas, the c-Jun/MyoD complex is recruited to the MyoD promoter to inhibit myogenesis (Bengal et al, 1992).…”

Directed mutation of the basic domain of v-Jun alters DNA binding specificity and abolishes its oncogenic activity in chicken embryo fibroblasts

“…Although deletion studies have demonstrated that cell transformation requires the general presence of the DNA binding domain , this need may result from speci®c conformational requirements necessary for protein ± protein interactions rather than speci®c DNA binding requirements. In support of this model, Jun is known to indirectly in¯uence the expression of promoters through non AP-1 binding sites as a result of interactions with a variety of non leucine zipper containing transcription factors such as the glucocorticoid receptor (GR), NF-kB, NF-1, MyoD, and NFAT (Bengal et al, 1992;Boise et al, 1993;Kerppola and Curran, 1993;Miner and Yamamoto, 1992;Robinson et al, 1995;SchuÈ le et al, 1990;Stein et al, 1993a,b;Touray et al, 1991;Yang-Yen et al, 1990. Many of these interactions require the presence of the DNA binding domain but do not necessarily require AP-1 target recognition.…”

Cross-family interaction between the bHLHZip USF and bZip Fra1 proteins results in down-regulation of AP1 activity

“…In Drosophila, a HLH protein emc lacking a basic motif, acts as a negative regulator of the bHLHZip protein achaete-scute (Ellis et al, 1990;Garrell and Modolell, 1990). Moreover, the bZip protein, Jun, and the bHLHZip protein, MyoD, form complexes and mutually down-regulate their transactivation (Bengal et al, 1992). Finally, it was reported that in vitro Fos interacts with FIP, a bHLHZip protein, closely related to USF (Blanar and Rutter, 1992), although the selectivity of this interaction was not well investigated.…”