Ha-ras oncogene strongly stimulates the activity of polyomavirus enhancer in transient expression assay. We found that the target of this stimulation in NIH3T3 cells was a 24 base pair long A element (from nt5107 to nt5130) within the enhancer. At least two nuclear factors in NIH3T3 cells, B and C, were detected by mobility shift assay in vitro to bind to this A element. We determined by transient expression assay that a target of stimulation by Ha-ras gene was the recognition site for B factor. In addition, the sequence within the A element which partly overlapped with the B factor binding site appeared to be also responsive to Ha-ras stimulation. In nuclear extract of NIH3T3 cells stably transformed by Ha-ras oncogene, however, binding of neither B nor C factors to the A element was detected by mobility shift assay. Instead, a new factor, D, emerged which shared the binding site with factor C. These dramatic changes in the behavior of the enhancer binding proteins may be the basis, at least partly, of a critical change in gene expression during the process of cell transformation by Ha-ras gene.
|Number of pages||10|
|Publication status||Published - 1988 Jan 1|
ASJC Scopus subject areas
- Molecular Biology
- Cancer Research