The ability of human papillomavirus E6 proteins to target p53 for degradation in vivo correlates with their ability to abrogate actinomycin D-induced growth arrest

Foster, Scott A.; Demers, G W; Etscheid, Beth G.; Galloway, Denise A.

doi:10.1128/jvi.68.9.5698-5705.1994

Cited by 174 publications

(89 citation statements)

References 45 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…In another study, targeted mutation of K11, K11E, was shown to completely impair E6 ability to induce p53 degradation in vitro and in human keratinocytes [Cooper et al, 2003]. Other variants that contained changes in amino acids previously shown to be important for p53 degradation [Foster et al, 1994], such as variant 1 (K10G) and 9 (K8Q), retained the capacity to induce p53 degradation in human keratinocytes ( Figs. 3 and 4) and in H1299 cells cotransfected with p53 [Lichtig et al, 2006].…”

Section: Discussionmentioning

confidence: 93%

Activities of human papillomavirus 16 E6 natural variants in human keratinocytes

Asadurian

Kurilin

Lichtig

et al. 2007

Journal of Medical Virology

View full text Add to dashboard Cite

Genetic variations in the E6 oncogene have been associated with different risk for cancer progression. In the present study, the functional significance of human papillomavirus (HPV) polymorphism in the E6 oncogene was investigated. Ten HPV16 E6 variants containing amino acid substitutions in the N-terminal region of E6 were evaluated for different biological and biochemical activities in human keratinocytes, the target cells for HPV infection. Western blot analyses of primary foreskin human keratinocytes or immortalized human keratinocytes, stably transduced with the E6 variants, revealed reduced p53 and Bax levels in all E6 expressing cultures. The reduction induced by most E6 proteins was at similar levels and comparable to the reduction induced by the E6 prototype. The ability of the proteins to induce serum/calcium-differentiation resistant colonies in primary keratinocytes was more variable. Overall activities of the variants ranged between 0.24- and 2.18-fold of the E6 prototype activity. The I27R/L83V variant showed the lowest activity whereas the R8Q variant showed the highest activity. The L83V polymorphism previously associated with risk for cancer progression in some populations, showed significant activity, comparable to that of the E6 prototype, in reducing p53 and Bax levels. Furthermore, this variant showed enhancement in the ability to induce colonies resistant to serum/calcium-triggered differentiation, however, the difference from the prototype was not statistically significant. This, and augmentation of other described functions might result in differences in L83V pathogenicity.

show abstract

Section: Discussionmentioning

confidence: 93%

Activities of human papillomavirus 16 E6 natural variants in human keratinocytes

Asadurian

Kurilin

Lichtig

et al. 2007

Journal of Medical Virology

View full text Add to dashboard Cite

show abstract

“…Conversely, while HPV 16 E6 expression has been found to sensitize mammary epithelial cells to apoptosis following DNA damage, mitomycin C, and staurosporine, this apparently occurred in a p53-independent manner [Xu et al, 1995]. HPV 16 E6 has been reported to have p53-independent activity including modulation of transcription [Foster et al, 1994], immortalization of mouse cells in conjunction with ras [Storey et al, 1995], and growth stimulation [Ishiwatari et al, 1994].…”

Section: Discussionmentioning

confidence: 99%

Human papillomavirus (HPV) 16 E6 sensitizes cells to atractyloside-induced apoptosis: Role of p53, ICE-like proteases and the mitochondrial permeability transition

et al. 1997

View full text Add to dashboard Cite

Infection of cervical epithelial cells with certain high risk HPV genotypes is thought to play an etiologic role in the development of cervical cancer. In particular, HPV type 16 and 18 early protein 6 (E6) is thought to contribute to epithelial transformation by binding to the tumor suppressor protein p53, targeting it for rapid proteolysis, resulting in loss of its cell cycle arrest and apoptosis-inducing activities. Recent data indicate that factors responsible for triggering apoptosis reside in the cytoplasm of cells, and not in the nucleus. In particular, the findings that mitochondria are required in certain cell-free models for induction of apoptosis and that bcl-2 is localized to mitochondria have focused attention on the role of the mitochondrial membrane permeability transition (MPT) in apoptosis. Here we present data to indicate that HPV 16 E6 expression sensitizes cells to MPT-induced apoptosis. We also report that HPV 16 E6 sensitization of cells to MPT-induced apoptosis occurs only in the presence of wildtype (wt) p53 expression. The extent of apoptosis induced by atractyloside (an inducer of the MPT) in normal, temperature-sensitive (ts) p53, and HPV-16 E6 transfected J2-3T3 cells, and the HPV expressing cervical carcinoma cell lines SiHa, Hela and CaSki was determined. C33A cells, which express mutant p53 but not HPV, were also exposed to atractyloside in the presence or absence of HPV 16 E6 expression. Dose-dependent apoptosis induced by atractyloside in normal J2-3T3 cells and cervical carcinoma cells was measured by loss of cell viability, nuclear fragmentation and DNA laddering. The sensitivity of cells to atractyloside-induced apoptosis was found to be: HPV 16 E6-J2-3T3 > CaSki > normal-J2-3T3 cells approximately ts p53-J2-3T3 approximately vector-J2-3T3 cells > Hela > SiHa > C33A approximately C33A 16 E6. Cyclosporin A (CsA), an inhibitor of the MPT, and ICE-I, a protease inhibitor, provided protection against atractyloside-induced apoptosis. These findings indicate that: 1) high risk HPV 16 E6 protein is capable of sensitizing cells to apoptosis; 2) HPV 16 E6 sensitization of cells to atractyloside-induced apoptosis occurs in a p53-dependent fashion; 3) the target of HPV 16 E6 sensitization of cells to atractyloside-induced apoptosis is the mitochondria; and 4) HPV 16 E6 sensitization of cells to atroctycoside-induced apoptosis involves an ICE-like protease-sensitive mechanism, regulating the onset of the MPT. These findings constitute the first evidence that mitochondria play a role in HPV 16 E6 modulation of apoptosis.

show abstract

“…This was not entirely surprising since in HPV-6 E6, 6 of 10 amino acids match those in the critical segment of HPV-16 E6. Although HPV-6 E6 appears to bind to p53 under some experimental conditions (11), in other experiments no binding of HPV-6 E6 was detected (18,55). In the experiments performed here with mouse cells as the source of p53, there was no binding to HPV-6 E6 or to LE6 or SE6.…”

Section: Discussionmentioning

confidence: 46%

Transforming properties of the cottontail rabbit papillomavirus oncoproteins Le6 and SE6 and of the E8 protein

Harry

Wettstein

1996

J Virol

View full text Add to dashboard Cite

Cottontail rabbit papillomavirus induces on cottontail and domestic rabbits papillomas which progress at a high frequency to carcinoma. The virus encodes three transforming proteins; one is translated from open reading frame (ORF) E7 and binds the retinoblastoma protein, and two, LE6 and SE6, are translated from the first and second ATGs of ORF E6, respectively. Here we show that neither of the E6 proteins coprecipitated with p53 in vitro, nor did they bind to a recently identified E6-binding protein (J. J. Chen, C. E. Reid, V. Band, and E. Androphy, Science 269:529-531, 1995). This protein was shown to bind to the E6 proteins of the high-risk human papillomavirus types 16 and 18 but not to the low-risk human papillomavirus types 6 and 11. In-frame deletions cloned into the pZipNeo vector were used to identify structural features of SE6 and LE6 important for transformation of NIH 3T3 cells. Three deletions covering the amino-terminal half of SE6 did not transform cells. In two of the three deletions, two Cys-X-X-Cys motifs were deleted, each deletion preventing the formation of one of the potential small Zn fingers of SE6. Among the LE6 deletions, only one had a reduced transformation efficiency, while seven transformed cells at least as efficiently as wild-type LE6. In each of three of these seven mutants, two Cys-X-X-Cys motifs were deleted. None of the three amino acid deletions which abolished transformation by SE6 reduced transformation by LE6. Furthermore, transformation did not correlate with the level of SE6 or LE6 proteins detectable. ORF E8 colinear with ORF E6, which could generate a 50-amino-acid protein with a hydrophobic segment, did not transform cells when cloned into the pZipNeo vector. However, mutation of the E8 ATG, which did not alter the amino acid sequence of LE6, increased transformation by LE6 without affecting the level of LE6 expression. The data suggest that transformation by the E6 proteins is not mediated by interfering with p53 function or through binding to the E6-binding protein. Furthermore, different structural features are important to maintain transformation functions and protein stability of LE6 and SE6. Finally, E8 seems not to be a transforming protein but rather appears to modulate transformation by LE6.

show abstract

The ability of human papillomavirus E6 proteins to target p53 for degradation in vivo correlates with their ability to abrogate actinomycin D-induced growth arrest

Cited by 174 publications

References 45 publications

Activities of human papillomavirus 16 E6 natural variants in human keratinocytes

Activities of human papillomavirus 16 E6 natural variants in human keratinocytes

Human papillomavirus (HPV) 16 E6 sensitizes cells to atractyloside-induced apoptosis: Role of p53, ICE-like proteases and the mitochondrial permeability transition

Transforming properties of the cottontail rabbit papillomavirus oncoproteins Le6 and SE6 and of the E8 protein

Contact Info

Product

Resources

About