Androgen-induced basic leucine zipper (AIBZIP)is a transcription factor. AIbZIP is a 395aa protein with homology to cyclic AMP-responsive element binding protein/activating transcription factor. It contains an NH(2)-terminal activation domain, a central bZIP domain, and a COOH-terminal transmembrane domain. Immunoreactive AIbZIP protein has been detected in the cytoplasm of prostatic luminal epithelial cells; full-length AIbZIP-GFP fusion proteins are localized in the cytoplasm of LNCaP cells, while a truncated form of AIbZIP lacking the putative transmembrane domain was exclusively nuclear. AIbZIP is expressed at higher levels in cancerous prostate cells compared with noncancerous prostate cells.