5'-flanking DNA of the human insulin receptor gene and long terminal repeat of mouse mammary tumour virus bind to the same nuclear protein(s).

The interaction of nuclear protein extracted from rat liver and 5'-flanking DNA of the human insulin receptor gene was investigated with the aid of gel mobility shift analysis. When 5'-flanking DNA (-1255/-1206 or -385/-345 base pairs) was incubated with nuclear protein, two or three 32P-DNA species (protein binding DNA fragment(s) and free DNA fragment) were detected. These bands did not disappear in spite of increasing amounts of synthetic poly(dI-dC), showing that nuclear protein binds specifically to 5'-flanking DNA of the insulin receptor gene. Increasing amounts of long terminal repeat of mouse mammary tumour virus resulted in a reciprocal decrease in nuclear protein binding to 5'-flanking DNA of insulin receptor gene. These results suggest that 5'-flanking DNA of insulin receptor gene binds to the same nuclear protein to which long terminal repeat of mouse mammary tumour binds.