FIG. 1.
Expression of DNp110 or DNp85 nearly completely abrogates EGF-stimulated induction of cyclin D1 protein expression, whereas expression of WTp110 potentiates it. Cells were transiently cotransfected with 1.5 μg each of pSV-βgal and an expression plasmid of a DN form of p110 (DNp110) or p85 (DNp85), wild-type p110 (WTp110), or an empty vector and made quiescent. Two days after transfection, the cells were stimulated with EGF (30 ng/ml) for 9 h, which corresponds to the late G1 R point. The expression of β-galactosidase (left) and cyclin D1 (right) was detected by double immunofluorescence as described in Materials and Methods. Identical fields in pairs are shown from a representative experiment. Arrowheads indicate positions of nuclei in transfected cells.