The minimal transforming fragment of HSV-2 mtrIII can function as a complex promoter element.

The minimal transforming fragment (486 TF) of HSV-2 mtrIII (0.567-0.570 map units) is composed of two distinct and non-overlapping promoter elements when linked to bacterial CAT genes. A 230-nucleotide fragment of 486 TF, Sal1-Hpa1, was active as a promoter element in primate cells but not rodent cells. A 173-nucleotide fragment, Sma1-Pst1, was active in both primate and rodent cells. The 486 TF did not compete for limiting cellular factors required to drive the CAT gene under control of the SV40 early promoter/enhancer. However, gel-retardation assays suggest that unique factors exist in cells transformed by HSV-2 which specifically recognized regions of 486 TF. These results are discussed with respect to HSV-2-mediated transformation.