Fig. 8. Expression of Egr1 in wild-type HaCaT cells and HaCaT cells transfected with an expression vector for the dominant-negative type II TGFß receptor. (A) Expression of the dominant negative type II TGFß receptor in two transfected HaCaT clones. The northern blot was probed with cDNA of the dnTGFßRII and with keratin 5 cDNA. Lane 1 shows HaCaT clone dn, which has a high expression level of the dnTGFßRII (2.4 kb). Lane 2 shows the very low expressing clone neo. Keratin 5 expression (2.6 kb) was used as loading control. (B) Northern blot analysis of RNA from HaCaT cells transfected with the dominant-negative type II TGFß receptor (wt) and transfectants (dn). Without addition of TGFß1, the expression of Egr1 in wild-type and transfectant cells is very low. Forty-five minutes after addition of 5 ng/ml TGFß1, the expression of Egr1 (3.2 kb) is strongly induced in untransfected HaCaT cells only. GAPDH expression (1.3 kb) was used as loading control. (C) Quantification of the northern blot analysis by PhosphorImager system. The expression level of Egr1 after addition of 5 ng/ml TGFß1 (+TGFß1) is elevated 24-fold in HaCaT cells and neo controls. By contrast, in HaCaT cells expressing the dominant-negative type II receptor at high levels (dn), only a ninefold increase is found.