The E7 proteins of the nononcogenic human papillomavirus type 6b (HPV-6b) and of the oncogenic HPV-16 differ in retinoblastoma protein binding and other properties.
The E7 early viral protein of the oncogenic human papillomavirus type 16 (HPV-16) has been strongly implicated in the maintenance of the malignant phenotype in cervical cancers and cancer-derived cell lines. HPV-16 E7 is a nuclear phosphoprotein that can cooperate with ras to transform baby rat kidney cells, transactivates the adenovirus E2 promoter, and binds to the retinoblastoma ( RB) protein. The E7 phosphoprotein of the nononcogenic HPV-6b, which is generally associated with benign genital warts, is similar to the HPV-16 E7 in amino acid sequence but differs dramatically in migration in sodium dodecyl sulfate-polyacrylamide gels, sedimentation in nondenaturing glycerol gradients, and the ability to bind the RB protein. Our results indicate that the RB protein preferentially binds the phosphorylated form of HPV-6b E7, which comprises a minor fraction of the total E7 expressed in transiently transfected COS-7 cells. These characteristics may help to explain the difference in the oncogenic potential of the oncogenic and nononcogenic types of genital papillomaviruses.[1]References
- The E7 proteins of the nononcogenic human papillomavirus type 6b (HPV-6b) and of the oncogenic HPV-16 differ in retinoblastoma protein binding and other properties. Gage, J.R., Meyers, C., Wettstein, F.O. J. Virol. (1990) [Pubmed]
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