CHARACTERIZATION OF THE PROMOTER REGION AND GENOMIC ORGANIZATION OF GLI, A MEMBER OF THE SONIC HEDGEHOG PATCHED SIGNALING PATHWAY

GLI is the prototype for the Gli-Kruppel gene family characterized by a consensus C-2-H-2 zinc finger domain and is believed to function as a transcription activator in the vertebrate Sonic hedgehog-Patched sig nal transduction pathway. Understanding GLI gene regulation may be of importance to understanding causes of human birth defects and cancer. To begin to understand the regulation of this developmentally importan t gene we have cloned the human GLI gene and functionally characterize d its 5' flanking region. The GLI gene is composed of 12 exons and 11 introns and in the zinc finger coding region shares a highly conserved splicing pattern with several other Gli family members in both verteb rates and C. elegans. A major transcription initiation site was identi fied upstream of the GLI translation start site along with three minor transcription initiation sites. The region surrounding the transcript ion initiation sites lacks TATA and CCAAT consensus sequences: has a h igh GC content, includes a CpG island, and contains several GC boxes. A 487 bp segment surrounding the transcription initiation sites increa sed expression of a luciferase reporter gene 15-fold in Tera-1 cells a nd was defined as the core promoter region of human GLI. In transgenic mice this region directed P-galactosidase expression to the central n ervous system on embryonic days 10.5-12.5 and to sites of endochondral ossification on embryonic days 12.5 and 13.5 in a pattern comparable to the endogenous expression pattern of mouse gli within these tissues . The previously identified gastrointestinal expression of gli was not driven by this region and may require elements outside of the core pr omoter. Sequence analysis of the 5' flanking region of the mouse gli g ene and the full-length mouse gli cDNA demonstrated high homology with human GLI, suggesting conservation of GLI regulation and function. (C ) 1998 Elsevier Science B.V.