Translational activation early in mitogenic activation of quiescent human T cells occurs at the level of translation initiation. Although eIF-2 alpha mRNA is very well translated in both quiescent and activated T cells, human Go lymphocytes contain very low levels of eIF-2 alpha message that are increased more than 50-fold during activation. Neither increased transcription of the eIF-2 alpha gene nor changes in the half- life of the message account for this rapid and large increase. We have therefore hypothesized that stabilization of the nuclear precursor sufficient to allow processing and transport to the cytoplasm might account for the large increase seen with mitogenic stimulation. During the course of mapping the promoter of the eIF-2 alpha gene by in vitro transcription, we found a divergent transcript that overlaps the eIF-2 alpha primary transcript for approximately 450 nucleotides. We have mapped this in vitro transcript by primer extension analysis and find that it maps to a region of the eIF-2 alpha gene that contains a consensus to the Initiator element described by Smale, Baltimore, and Reinberg. This initiator sequence is oriented to generate an antisense transcript. By RT-PCR we have confirmed in vivo expression of both the sense and antisense transcripts. In Go T cells formation of ds-RNA leads to rapid degradation of the sense transcript, thereby inhibiting accumulation of eIF-2 alpha mRNA. Upon mutagenic activation, transcription of the antisense gene is inhibited. By preventing ds-RNA formation, stabilization of the primary sense transcript is increased and processing and accumulation of the eIF-2 alpha mRNA can occur.
