PROPERTIES OF A NOVEL GENE ISOLATED FROM A HODGKINS-DISEASE CELL-LINETHAT IS EXPRESSED EARLY DURING LYMPHOID-CELL ACTIVATION

We have isolated a novel 667-bp cDNA clone, designated epag, from a Ho dgkin's-disease cell line-derived library that is expressed in associa tion with T cell activation and which is not related to any known gene family. By using reverse transcription/PCR, we have demonstrated that epag mRNA is expressed as early as 1 h after stimulation of normal PB MCs with anti-CD3. The levels of mRNA peaked by 4 h, and no expression was detectable by 12 h postactivation or in resting cells incubated i n culture without activation. Expression of epag was also detected in PMA- and PHA-stimulated, but not in nonstimulated Jurkat cells, and ov erall its expression in transformed cell lines of hemopoietic origin i s highly restricted. Sequence analysis of multiple independent cDNA cl ones showed that epag expressed in the Hodgkin's-disease cell line L42 8 is identical to the gene expressed in normal activated PBMC. Epag ex pression was detected by reverse transcription/PCR in RNA preparations made from various normal nonlymphoid tissues. Computer analysis of th e sequence identified an open reading frame encoding a putative protei n of 13.2 kDa initiating at a CUG translational codon. In vitro transl ation and Western blot analysis with anti-peptide serum supported this analysis. We hypothesize that epag functions as an early signal that helps mediate the activation of T cells.