The human junD gene is positively and selectively autoregulated

The junD gene is much less inducible than that of the two other members of the jun family; c-jun and junB, and is constitutively expressed in most tissues. We cloned the promoter of the human junD (hjunD) gene and found that it contains multiple cis-acting elements, most of which are conserved from chicken to human. Those included the TATA box, TRE, the CAAT box (referred to as the CTT complex), CREs, an Oct motif, and a number of GC boxes, most probably the recognition site for the SP1 transcription factor. The enhancer of the gene was localized to the -83 to -194 region that contains a GC box and an Oct motif. The CTT complex is shared by the promoters of the three jun genes, but each with a unique TRE. We show here that the hjunD TRE binds proteins that are related, but not identical, to the classical AP1 complex. We demonstrate by transfection experiments that the hjunD promoter is preferentially regulated by hjunD, through its unique TRE, generating a positive autoregulatory loop that might be responsible for its constitutive expression.