TABLE 5.

Levels of Ras Protein and AP-1 Transactivating Activity

Clone	Vector	MGSA/GROβ	MGSA/GROγ	MGSA/GROα
Ras protein expression level (fold)	1	4.15 ± 0.65	3.25 ± 0.05	7.00 ± 0.90
Basal AP-1 transactivation (fold)	1	1.12 ± 0.32	2.10 ± 0.18	3.16 ± 0.45
Dominant-negative Ras inhibits AP-1 transactivation	0.54 ± 0.10		0.48 ± 0.01	0.43 ± 0.12

The level of Ras protein and AP-1 transactivating activity were monitored by Western blot and by luciferase activity in the MGSA/GROα-, β-, and γ-expressing melan-a clones as described in Materials and Methods. The luciferase and β-Gal activities were measured 48 h after transfection. Transfection efficiency was normalized by comparing AP-1 luciferase activity to β-galactosidase activity. The data are reported as mean ± SEM fold induction (the relative luciferase activity of MGSA/GROα, β, γ divided by the relative luciferase activity of the vector) from three independent experiments. In experiments involving dominant-negative Ras transfection, the results are reported as mean fold inhibition ± SEM (the relative luciferase activity of dominant-negative form of M-Ras divided by the relative luciferase activity of pBK-CMV vector) from three independent experiments. Co-transfection of the dominant negative Ras expression construct with the AP-1 luciferase reporter construct resulted in a marked reduction in endogenous AP-1 reporter activity.