FIG. 8.

(A) Inhibition of Ras activity by UVB in HEKn and HEKn-E6/E7 but not in HaCaT cells. Cells (plated and maintained in BKM+exoGF) were irradiated with the indicated doses of UVB, and the levels of GTP loading of Ras (and ERK phosphorylation in the case of HaCaT cells) were determined by immunoblot analysis at the indicated times after the irradiation as described in the text. (B) Existence of a multiprotein complex containing Sos1, Grb2, and ShcA in untreated or UVB-treated HEKn. HEKn (grown in BKM+exoGF) were treated with UVB (1,200 J/m²). Sos1 was immunoprecipitated 30 min later, and the presence of Sos1, Grb2, and the three forms of ShcA (p46, p52, and p66) in the immunoprecipitate was detected in immunoblot analyses.