Murine cre ! Transcription Is Rapidly Induced in T-CeIls and Fibroblasts by Mitogenic Agents and the Phorbol Ester 1 2O TetradecanoyIphorboI . 1 3-acetate 1

Abstrad The c-re! protooncogene is here shown to be a member of the early response gene family. Expression induced by different agents is regulated by both transcriptional and posttranscriptional mechanisms. In quiescent fibroblasts, c-re! expression is maximally induced by serum or 1 2-O-tetradecanoylphorbol-1 3-acetate within 60 mm and is superinduced in serum-stimulated fibroblasts by cycloheximide. In T-cells, although 12-0tetradecanoylphorbol-13-acetate and concanavalin A both rapidly adivate c-re! expression, the kinetics of indudion mediated by these agents differs markedly. Nuclear run-on analysis demonstrates that induced cre! expression is due primarily to increased transcription, and the rapid decrease in expression observed in serumand 1 2-O-tetradecanoylphorbol13-acetatestimulated cells results from mRNA turnover. In the Blymphoid lineage, c-re! is constitutively transcribed, with the differentiation stage-specific decrease in c-re! expression seen in plasmacytomas refleding posttranscriptional regulation.