MOLECULAR CHARACTERIZATION OF MOUSE T-CELL ECTO-ADP-RIBOSYLTRANSFERASE RT6 - CLONING OF A 2ND FUNCTIONAL GENE AND IDENTIFICATION OF THE RT6GENE-PRODUCTS

RT6 is an enzymatically active GPI-anchored membrane protein that was originally discovered in the rat as a peripheral T cell alloantigen. I t has attracted interest as an activation antigen and because defectiv e RT6-expression coincides with increased susceptibility for autoimmun e type I diabetes in the BE rat. Southern blot analyses indicate that the rat carries a single copy RT6 gene whereas the mouse carries a dup lication of the homologous locus. We had previously cloned and sequenc ed a RT6-homologous cDNA from BALB/c mouse spleen. We now report the c loning and characterization of a second RT6-homologue from BALB/c and 129/Sv mice. The two mouse Rt6 genes (designated Rt6-1 and Rt6-2) enco de similar open reading frames that are disrupted by conserved introns . The nucleotide sequences of the Rt6-1 and Rt6-2 coding regions show 87% sequence identity, the deduced amino acid sequences 79% identity. The amino acid sequences reveal significant similarity to recently clo ned ADP-ribosylating ectoenzymes from rabbit and human skeletal muscle as well as chicken bone marrow cells. RT-PCR analyses reveal that the two Rt6 genes are differentially expressed in distinct inbred mouse s trains and that their transcripts are properly processed. Western blot analyses demonstrate that the respective gene products are released f rom cells by treatment with PI-PLC. The results further show that both mouse Rt6 genes are translated into GPI-anchored cell surface molecul es and that Rt6 gene expression is restricted to peripheral lymphoid t issues. Copyright (C) 1996 Elsevier Science Ltd.