Gene structure, promoter characterization, and basis for alternative mRNA splicing of the human CD58 gene

The 60-kDa lymphocyte function-associated Ag-3 (LFA-3/CD58), a highly glycosylated adhesion molecule that serves as ligand for the T cell-restricted glycoprotein CD2, is encoded by a gene at the human chromosome locus 1p13. We have elucidated the exon-intron organization of the entire human CD58 gene, including approximately 2.5 kilobases (kb) of 5'-flanking DNA. Four overlapping genomic clones, spanning approximately 65 kb, contained the entire approximately 1-kb coding sequence of CD58 and consisted of six separate exons, which varied from 72 to 294 bp in size. At least two different CD58 mRNA precursors can be generated from the human gene as a result of alternative choice of one of the two acceptor splice sites located within exon 5. DNA sequence analysis of about 2.5 kb of 5'-flanking sequence of the CD58 gene indicated the absence of a CAAT box. However, potential binding sites for the transcriptional activators AP-2, GATA, PU.1, and Sp-1 are present. Two consensus TATAA elements, located approximately 2.4 kb upstream of the transcriptional start site, have been identified. The 2.5-kb CD58 promoter sequence displayed functional activity in transient transfection assays in the hepatocellular carcinoma cell line HepG2. Comparing the response of CD58 promoter-driven luciferase plasmids to several cytokines and other agents suggests that the CD58 promoter is regulated by up-regulatory, enhancer-like and down-regulatory, silencer-like elements. Further analysis of this region should allow researchers to gain insight into the molecular mechanisms by which this gene is regulated, e.g., during inflammatory responses.