We are investigating the consequences of mitogen mediated signals to T cells isolating and characterizing genes that constitute the immediate early by transcriptional response to these events. Primary sequence analysis has revealed that a large number of early induced genes code for transcription factors. A variety of structural classes of factors have been observed, including 3 zinc-finger containing proteins (pAT 225, 133, and 591), a protein related to the steroid receptor family of transcription factors (pAT 416), and two rel-related members of the NF-(kappa)B-binding transcription complex (pAT 243 and 189). Additional clones have been described for a putative GTP-binding protein (pAT 270, RAI-1), a phosphotyrosine phosphatase (pAT 120, CAP-1), a hematopoietic cell-specific membrane protein (pAT 237), and a 158 amino acid peptide that contains a hydrophobic leader sequence, but appears to be cell-associated (pAT 154). Structural and functional analyses are proceeding on selected clones.