Transcriptional Enhancement of the Human Gene Encoding for a Melanoma‐associated Antigen (ME491) in Association with Malignant Transformation

A cloned DNA fragment (λR31) containing the human gene for melanoma‐associated ME491 antigen was transfected into mouse fibroblast cell lines and the antigen expression was studied. Our preliminary observation of higher expression of the antigen in more malignant Ltk cells and weaker expression in less malignant NIH3T3 cells tempted us to investigate the antigen expression in Harvey (H)‐ras‐transformed NIH3T3 cells. It was observed that malignant transformation of the λR31‐transfected NIH3T3 cells by H‐ras oncogene enhanced the antigen expression to some extent. Northern blot analysis suggested that the enhancement occurred at the transcriptionsl level. Nucleotide sequence analysis of the 5′‐regulatory region of the ME491 antigen gene in λR31 identified a number of consensus sequence motifs for binding of transcription factors such as Sp1, AP‐2 and polyomavirus enhancer binding proteins 2 and 3. A consensus sequence motif for binding of AP‐1, known as a ras‐responsive element, was not found in that region. The significance and possible involvement of the transcription factors in the enhancement of ME491 antigen expression are discussed.