The serum and TPA responsive promoter and intron-exon structure of EGR2, a human early growth response gene encoding a zinc finger protein

Abstract

EGR2 is a human zinc finger encoding gene whose expression is induced with fos-like kinetics by diverse mitogens in several cell types. Since its cDNA sequence predicts a protein which contains zinc finger motifs, EGR2 may play a transcriptional regulatory role in cellular proliferation. The present study was undertaken to: 1) examine the genomic organization and 5' flanking sequence of EGR2 so as to identify upstream regulatory elements; 2) test whether these elements are functional in gel shift assays and by transient expression; and 3) examine whether pathways other than protein kinase C lead to serum induction of EGR2, and if they do, ask whether the different pathways converge on a serum response element. The EGR2 gene spans 4.3 kb and has one intron. The translation initiation site is located within the first exon. The transcription start site of EGR2 was determined by S1 nuclease and primer extension analysis and a TATA box was identified 28 bp upstream. Two putative serum response elements, designated CArG-1 and CArG-2 were identified in the 5' flanking sequence. By deletion analyses and mutagenesis, serum and PMA responsiveness of the cloned EGR2 promoter region was traced to the CArG-1 region in transient CAT assays performed in NIH 3T3 cells. Both protein kinase C dependent and independent pathways were found to converge on the CArG-1 box to induce the expression of EGR2.