The Transcriptional Factor Egr-1 Is Synthesized by Baculovirus-Infected Insect Cells in an Active, DNA-Binding Form

The Egr-1 (zfp-6) gene encodes a zinc-finger-containing nuclear protein that is rapidly and transiently induced in quiescent cells treated with mitogens. We have constructed baculovirus vectors that synthesize mouse Egr-1 protein initiating at two putative ATG start sites. The ATG site producing the larger protein (Mr, 80,000) is similar, if not identical, to Egr-1 synthesized by serum-stimulated quiescent mouse fibroblasts, thus identifying the likely site for translation. The protein synthesized by the insect cells is active as assayed by its ability to bind to a specific DNA sequence that has been identified as an Egr-1 binding site. The insect cell system will allow further studies of the structure and function of the Egr-1 product, a protein that appears to be an important "master switch" for other genes.