FIG. 9.

CHOP and ATF6 are capable of gene expression regulation by tethering to a preexisting complex. A proposed model for the interaction between CHOP and the AP-1 complex is shown in parallel to the one previously described for ATF6 and SRF (44, 53). Tethering of bZIP proteins to preexisting DNA-protein complexes is a new mechanism by which bZIP transcription factors regulate gene expression. In this case, both CHOP and ATF6 are downstream effectors of the stress-induced p38 MAPK pathway. The tethering mechanism described may facilitate the regulation of a large number of genes by a limited number of transcription factors. This circumstance may have an important significance when cells are exposed to damaging or stressful conditions.