Isolation and characterization of the gene encoding mouse tax-responsive element-binding protein (TREB) 5

TREB5/hXBP-1/HTF is a basic region leucine zipper protein which binds to a cyclic AMP responsive element (CRE)-like element in both human T-cell leuke mia virus type 1 and human major histocompatibility complex (MHC) class II genes. To analyze the structure and transcription regulation of the TREES g ene, we isolated the mouse TREES gene and cDNA. The mouse TREES gene contai ns five exons and four introns and spans approximately 5 kb. The deduced am ino acid sequence of mouse TREES exhibited 77% and 94% homology to human an d rat TREB5, respectively. The b-zip structure is completely conserved in m ouse, rat and human. Southern blot analysis of the mouse genomic DNA demons trated that positive bands exactly coincide with those expected from sequen ces of the cloned genes, indicating that the mouse TREES gene is present as a single copy. The transcription start site of the mouse TREES gene was ma pped to -15 bp upstream from the ATG initiation codon. Promoter analysis of serial deletion mutants revealed that the -142 bp upstream region is the m inimum sequence to promote mouse TREES gene expression and that the -1.0 kb upstream region is required for full promoter activity.