The human EGF receptor gene: structure of the 110 kb locus and identification of sequences regulating its transcription.

The human epidermal growth factor receptor (EGFR) proto-oncogene is shown to span 110 kb of DNA divided into 26 exons. Analysis of sequences surrounding exon 1 reveals a highly CG rich region which promotes transcription. The activity of the EGF receptor promoter can be modulated by E1A protein and receptor RNA levels increased by stimulation with phorbol ester or fetal calf serum. Promoter activity is assayed by linkage to the chloramphenicol acetyl transferase gene and transfection in three cell lines, with quantitation of plasmid DNA uptake by isolation of a Hirt supernatent from each transfection. Deletion analysis of the CG rich promoter region of the gene and construction of chimeric EGFR/SV40 promoters are used to demonstrate positive transcription elements located both within exon 1 and 5' to the start of transcription. Negative regulation of transcription by sequences within a -140 to +80 region is suggested. Cotransfection experiments suggest a requirement for the interaction of DNA binding protein Sp1 for maximal activity. Finally, derepression of a positive regulatory sequence located in exon 1 during cotransfection experiments is shown. Results are discussed in reference to the multilevel regulation of EGF receptor expression.