Genome and proteins of HPV21. [GT1] (a) Schematic illustration of HPV21 genome. The genome structures of beta-HPVs conform to the overall genome structures of alpha-HPVs except that beta-HPVs do not encode an early protein, E5. The genome of HPV21 consists of 7.9 kb circular double stranded DNA. The viral genome encode five early proteins (designated as E1, E2, E4, E6 and E7) and two late proteins (designated as L1 and L2) that are viral capsid proteins. The viral genome contains a non-coding region (NCR) that contains the major promoter for the transcription of early genes. The early genes E6 and E7 constitute the transforming genes. (b) Schematic illustration of the E6 proteins of EV-associated beta-HPVs. The unique N-terminal domains of the E6 proteins of HPV14, HPV21 and HPV20 are compared with the FOXK1/K2-interacting motif of HAdv5 E1A in the boxed area.[GT2]