To further analyze a possible co-operation of Rac1 and HPV-8 in skin papilloma formation, we generated double transgenic K14 HPV-8/K14 L61Rac1 mice expressing HPV-8 and, in addition, an activating mutant of Rac1, L61Rac1 [19], both under the control of the K14 promoter (Table 1, Figure 2C). Here, KRT14 is linked to skin papilloma.