STRUCTURE OF THE GENE ENCODING THE RAT T-CELL ECTO-ADP-RIBOSYLTRANSFERASE RT6

Cellular functions, such as the cytolytic potential of CTLs, can be re gulated by mono-ADP-ribosylation of target proteins. Recently, the T c ell differentiation marker RT6 has been shown to possess mono-ADP-ribo syltransferase activity. Defects in RT6 expression coincide with incre ased susceptibility in animal models for insulin-dependent diabetes me llitus and other autoimmune diseases. We present an analysis of the ra t RT6 gene, providing a basis for studying the regulation of this gene in T cells of normal and diabetes-prone rats. If is the first structu ral analysis of a mammalian mono-ADP-ribosyltransferase gene. The RT6 gene consists of eight exons spanning approximately 20 kb, The proxima l four exons encode 5' untranslated region sequences and are found in multiple alternatively spliced variants. Exon 5 encodes the N-terminal signal sequence. An unusually large exon 7 encodes the entire native polypeptide. The final exon 8 encodes the C-terminal signal sequence f or glycosylphosphatidylinositol anchor attachment and the 3' untransla ted region. Two independent TATA box-containing promoters associated w ith exons 1 and 2 were identified, and their activity was verified in transient transfection assays. The distal promoter displays elements c ontained in the regulatory regions of T cell-specific genes, such as e ts and ikaros, Analysis of RT6 transcripts showed that this promoter i s the major one in adult rat spleen cells. The 3' end or the gene does not display alternative splicing. However, two polyadenylation signal s are found in the 3' untranslated region.