Close encounters of many kinds: Fos-Jun interactions that mediate transcription regulatory specificity

Fos and Jun family proteins regulate the expression of a myriad of genes in a variety of tissues and cell types. This functional versatility emerges f rom their interactions with related bZIP proteins and with structurally unr elated transcription factors. These interactions at composite regulatory el ements produce nucleoprotein complexes with high sequence-specificity and r egulatory selectivity. Several general principles including binding coopera tivity and conformational adaptability have emerged from studies of regulat ory complexes containing Fos-Jun family proteins. The structural properties of Fos-Jun family proteins including opposite orientations of heterodimer binding and the ability to bend DNA can contribute to the assembly and func tions of such complexes. The cooperative recruitment of transcription facto rs, coactivators and chromatin remodeling factors to promoter and enhancer regions generates multiprotein transcription regulatory complexes with cell - and stimulus-specific transcriptional activities. The gene-specific archi tecture of these complexes can mediate the selective control of transcripti onal activity.