Isolation of Flat Revertants from Human Papillomavirus Type 18 E6E7 Transformed 3Y1 Cells by Transfection with a Rat Embryo Fibroblast cDNA Expression Library

Abstract

A rat embryo fibroblast (REF) cDNA expression library was transfected into 3Y1 cells transformed by human papillomavirus type 18 E6 and E7 genes and 10 flat revertants were isolated. These revertants expressed the same levels of E6 and E7 mRNA as the parent cells, but had greatly reduced ability to form colonies in soft agar. Suppression of transformation was dominant in cell hybrids generated by fusing each revertant with the parental transformed cells. Furthermore, loss of transfected cDNA was observed in re-transformed cell hybrids derived from one flat revertant. Over expression of the CDNA suppresses the colony-forming efficiency of the cells transformed by E6 and E7 genes.