Mutations of the human papillomavirus type 16 E7 gene that affect transformation, transactivation and phosphorylation by the E7 protein

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Abstract
The human papillomavirus type 16 (HPV-16) E7 gene cooperates with an activated ras oncogene to transform primary rodent cells and is important in the immortalization of cervical keratinocytes. We have generated a series of point mutations within the E7 gene and show that mutation of residues serine 31 and serine 71 affect the phosphorylation of the E7 protein, but do not alter its ability to cooperate with ras. Further mutations which alter cysteine residues in a -Cys-X-X-Cys- motif decrease transformation markedly, although they do not abolish it entirely. All the mutations generated displayed a decreased ability to transactivate the adenovirus E2 promoter. These results show that neither phosphorylation of E7 nor its ability to transactivate are required for transformation by E7.