Characterization of the promoter region of the human c-erbB-2 protooncogene.

Three overlapping genomic clones that contain the 5'-terminal portion of the human c-erbB-2 gene (ERBB2) were isolated. The promoter region was identified by nuclease S1 mapping with c-erbB-2 mRNA. Seven transcriptional start sites were identified. DNA sequence analysis showed that the promoter region contains a "TATA box" and a "CAAT box" about 30 and 80 base pairs (bp), respectively, upstream of the most downstream RNA initiation site. Two putative binding sites for transcription factor Sp1 were identified about 50 and 110 bp upstream of the CAAT box, and six GGA repeats were found between the CAAT box and the TATA box. This region had strong promoter activity when placed upstream of the bacterial chloramphenicol acetyltransferase gene and transfected into monkey CV-1 cells. These data indicate that the promoter of the human c-erbB-2 protooncogene is different from that of the protooncogene c-erbB-1 (epidermal growth factor receptor gene), which does not contain either a TATA box or a CAAT box. Comparison of the promoter sequences and activities of the two protooncogenes should be helpful in analysis of the regulatory mechanism of expression of their gene products, which are growth-factor receptors.