E7 protein

Figure 26.1 Immortalization of human cells Cells enter replicative senescence at mortality stage 1 (Ml Hayflick limit) after about 60 population doublings (PD). The protein p 16 accumulates in senescent cells. The simian virus 40 (SV40) large T antigen as well as the human papilloma virus (HPV) type 16-E6 and E7 proteins sequester the retinoblastoma protein (Rb) and/or p53 constitutively releases the transcription factor E2F. E2F induces expression proteins required for progression through Gl/S transition, thus the cells escape cell cycle arrest. At mortality stage 2 (M2), transformed cells must overcome senescence and crisis before they are immortalized. This is likely to involve the activation of telomerase either by the introduction of hTERT cDNA or by a genetic change that activates telomerase.

Clinical studies with a recombinant vaccine (using Vaccinia virus expressing HPV 16, 18, E6, and E7 proteins) in patients with preinvasive and invasive cancer have been reviewed (1). 

HPV-16 encodes a set of early gene oncoproteins (E6 and E7) responsible for cellular immortalization. HPV types 16 and 18 E6 and E7 proteins are known to interact strongly with p53 and retinoblastoma (Rb) tumor suppressor gene products, respectively (2). The association of E6 with p53 marks this tumor suppressor for rapid ubiquitin-mediated proteolysis. Reduced levels of p53 prevent the cell from activating cell cycle arrest and/or induction of apoptosis in genetically mutated cells. 

Quantitatively assessing oncoproteins in HPV-transformed cells is useful for evaluating viral activity and the potential effectiveness of antiviral therapy (4). The following describes immunodetection methods for assaying levels of human papillomavirus E6 and E7 protein in total protein cell lysates. This pro-... 

Similar to two-hybrid screens, SPRi can be used to detect conditions under which proteins do not interact. The interaction of human papillomavirus E7 protein and retinoblastoma tumor suppressor protein RB was studied by Jung and co-workers [49]. Fifteen hundred protein spots containing immobilized E7 protein were produced, and an interaction with added RB protein was detected using SPR. The addition of a peptide derived from a motif on E7 along with RB has been observed to clearly disrupt the interaction through lack of an SPR signal. The one peptide discussed in this study can easily be replaced with an array of... 

Another manifestation of genetic instability is an abnormal number of centro-somes. Centrosomes can be stained and quantified in an assay using anti-centrin antibodies. Both, genetic instability and loss of genomic integrity, are often posttransformation events. However, under certain circumstances they can contribute to cellular transformation directly. An example is the transformation by the human papillomavirus (HPV) E7 protein. The HPV E7 and E6 proteins are the two HPV oncogenes found in 99.3% of all cervical cancers. 

UTS Biotech, Rome, Italy Human papillomavirus 16 E7 protein 210, 211... 

Other sensor platforms have also been explored, such as surface plasmon resonance, field-effect transistors, other optical/spectrophotometric methods, for example, Raman spectroscopy and chemiluminescence, and electrochemical techniques. Very recently, Cai et al. have demonstrated that arrays of carbon-nanotube tips with an imprinted nonconducting polymer coating can recognize proteins below the picograms per liter level, using electrochemical impedance spectroscopy. Devices for the specific recognition of human ferritin and human papillomavirus-derived E7 protein were described (Figure 34). 

Bermudez-Humaran, L.G., Langella, P, Miyoshi, A., et al. (2002) Production of human papillomavirus type 16 E7 protein in Lactococcus lactis. Appl Environ Microbiol 68, 917-922. 

Li, Y., Li, X., liu, H., et al. (2014) Intranasal immunization with recombinant lactococci carrying human papillomavirus E7 protein and mouse interleukin-12 DNA induces E7-specific antitumor effects in C57BL/6 mice. Oncol Lett 7, 576-582. 

Munger, K., Wemess, B.A., Dyson, N., et al. (1989) Complex formation of human papillomavirus E7 proteins with the retinoblastoma mmor suppressor gene product. EMBO J 8, 4099-4105. 

Whitehead, M., Ohlschlager, R, Almajhdi, F.N., et al. (2014) Human papillomavirus (HPV) type 16 E7 protein bodies cause tumour regression in mice. BMC Cancer 14, 367. 

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