SMAD2 and squamous cell carcinoma: These include our observation that MmuPV1 contains separate promoters for E6 and E7, and the additional facts that MmuPV1 causes squamous cell carcinomas at cutaneous sites [57], lacks an E5 ORF [4] and encodes an E6 protein that shares with HPV8 E6 the ability to bind MAML1 and SMAD2/SMAD3 but not E6AP and p53 [58].