scholarly journals Restoration of telomeres in human papillomavirus-immortalized human anogenital epithelial cells.

1994 ◽  
Vol 14 (2) ◽  
pp. 961-969 ◽  
Author(s):  
A J Klingelhutz ◽  
S A Barber ◽  
P P Smith ◽  
K Dyer ◽  
J K McDougall
Keyword(s):  
Human Papillomavirus ◽  
Epithelial Cells ◽  
Telomere Length ◽  
Open Reading Frames ◽  
Population Doubling ◽  
Telomere Shortening ◽  
Human Papillomavirus Type 16 ◽  
Immortalized Cells ◽  
E6 And E7

Loss of telomeres has been hypothesized to be important in cellular senescence and may play a role in carcinogenesis. In this study, we have measured telomere length in association with the immortalization and transformation of human cervical and foreskin epithelial cells by the human papillomavirus type 16 or 18 E6 and E7 open reading frames. By using a telomeric TTAGGG repeat probe, it was shown that the telomeres of precrisis normal and E6-, E7-, and E6/E7-expressing cells gradually shortened with passaging (30 to 100 bp per population doubling). Cells that expressed both E6 and E7 went through a crisis period and gave rise to immortalized lines. In contrast to precrisis cells, E6/E7-immortalized cells generally showed an increase in telomere length as they were passaged in culture, with some later passage lines having telomeres that were similar to or longer than the earliest-passage precrisis cells examined. No consistent association could be made between telomere length and tumorigenicity of cells in nude mice. However, of the three cell lines that grew in vivo, two had long telomeres, thus arguing against the hypothesis that cancer cells favor shortened telomeres. Our results indicate that arrest of telomere shortening may be important in human papillomavirus-associated immortalization and that restoration of telomere length may be advantageous to cells with regard to their ability to proliferate.

Restoration of telomeres in human papillomavirus-immortalized human anogenital epithelial cells

1994 ◽  
Vol 14 (2) ◽  
pp. 961-969
Author(s):  
A J Klingelhutz ◽  
S A Barber ◽  
P P Smith ◽  
K Dyer ◽  
J K McDougall
Keyword(s):  
Human Papillomavirus ◽  
Epithelial Cells ◽  
Telomere Length ◽  
Open Reading Frames ◽  
Population Doubling ◽  
Telomere Shortening ◽  
Human Papillomavirus Type 16 ◽  
Immortalized Cells ◽  
E6 And E7

Loss of telomeres has been hypothesized to be important in cellular senescence and may play a role in carcinogenesis. In this study, we have measured telomere length in association with the immortalization and transformation of human cervical and foreskin epithelial cells by the human papillomavirus type 16 or 18 E6 and E7 open reading frames. By using a telomeric TTAGGG repeat probe, it was shown that the telomeres of precrisis normal and E6-, E7-, and E6/E7-expressing cells gradually shortened with passaging (30 to 100 bp per population doubling). Cells that expressed both E6 and E7 went through a crisis period and gave rise to immortalized lines. In contrast to precrisis cells, E6/E7-immortalized cells generally showed an increase in telomere length as they were passaged in culture, with some later passage lines having telomeres that were similar to or longer than the earliest-passage precrisis cells examined. No consistent association could be made between telomere length and tumorigenicity of cells in nude mice. However, of the three cell lines that grew in vivo, two had long telomeres, thus arguing against the hypothesis that cancer cells favor shortened telomeres. Our results indicate that arrest of telomere shortening may be important in human papillomavirus-associated immortalization and that restoration of telomere length may be advantageous to cells with regard to their ability to proliferate.

scholarly journals Targeted expression of the E6 and E7 oncogenes of human papillomavirus type 16 in the epidermis of transgenic mice elicits generalized epidermal hyperplasia involving autocrine factors.

1994 ◽  
Vol 14 (12) ◽  
pp. 8250-8258 ◽  
Author(s):  
P Auewarakul ◽  
L Gissmann ◽  
A Cid-Arregui
Keyword(s):  
Human Papillomavirus ◽  
Growth Factor ◽  
Epithelial Cells ◽  
Transgenic Mice ◽  
Transforming Growth Factor ◽  
Basal Layer ◽  
Epidermal Hyperplasia ◽  
Human Papillomavirus Type 16 ◽  
E6 And E7

The E6 and E7 early genes of human papillomavirus type 16 have been shown in vitro to play a central role in the transforming capability of this virus. To explore their effects on differentiating epithelial cells in vivo, we used a bovine cytokeratin 10 (K10) promoter to target the expression of E6 and E7 to the suprabasal layers of the epidermis of transgenic mice. In two different lines of mice efficiently expressing the transgene, animals displayed generalized epidermal hyperplasia, hyperkeratosis and parakeratosis in the skin and the forestomach, both known to be sites of K10 expression. Northern (RNA) blot analysis revealed high levels of E6 and E7 transcripts, and in situ hybridizations localized these transcripts to the suprabasal strata of epidermis. In vivo labeling of proliferating cells showed two distinct effects of E6 and E7 expression in the epidermis: (i) an increase in the number of growing cells in the undifferentiated basal layer and (ii) abnormal proliferation of differentiated cells in the suprabasal strata. The expression of c-myc in the skin of transgenics was higher than that in control animals. The induction of c-myc transcription by topical application of tetradecanoyl phorbol acetate was prevented by simultaneous treatment with transforming growth factor beta 1 in nontransgenic skin but not in transgenic skin. In addition, transforming growth factor alpha was found to be overexpressed in the suprabasal layers of the transgenic epidermis. These findings suggest that autocrine mechanisms are involved in the development and maintenance of epidermal hyperplasia. Animals of both lines developed papillomas in skin sites exposed to mechanical irritation and wounding, suggesting that secondary events are necessary for progression to neoplasia. Collectively, these results provide new insights into the tumor promoter activities of human papillomavirus type 16 in epithelial cells in vivo.

Targeted expression of the E6 and E7 oncogenes of human papillomavirus type 16 in the epidermis of transgenic mice elicits generalized epidermal hyperplasia involving autocrine factors

1994 ◽  
Vol 14 (12) ◽  
pp. 8250-8258
Author(s):  
P Auewarakul ◽  
L Gissmann ◽  
A Cid-Arregui
Keyword(s):  
Human Papillomavirus ◽  
Growth Factor ◽  
Epithelial Cells ◽  
Transgenic Mice ◽  
Transforming Growth Factor ◽  
Basal Layer ◽  
Epidermal Hyperplasia ◽  
Human Papillomavirus Type 16 ◽  
E6 And E7

The E6 and E7 early genes of human papillomavirus type 16 have been shown in vitro to play a central role in the transforming capability of this virus. To explore their effects on differentiating epithelial cells in vivo, we used a bovine cytokeratin 10 (K10) promoter to target the expression of E6 and E7 to the suprabasal layers of the epidermis of transgenic mice. In two different lines of mice efficiently expressing the transgene, animals displayed generalized epidermal hyperplasia, hyperkeratosis and parakeratosis in the skin and the forestomach, both known to be sites of K10 expression. Northern (RNA) blot analysis revealed high levels of E6 and E7 transcripts, and in situ hybridizations localized these transcripts to the suprabasal strata of epidermis. In vivo labeling of proliferating cells showed two distinct effects of E6 and E7 expression in the epidermis: (i) an increase in the number of growing cells in the undifferentiated basal layer and (ii) abnormal proliferation of differentiated cells in the suprabasal strata. The expression of c-myc in the skin of transgenics was higher than that in control animals. The induction of c-myc transcription by topical application of tetradecanoyl phorbol acetate was prevented by simultaneous treatment with transforming growth factor beta 1 in nontransgenic skin but not in transgenic skin. In addition, transforming growth factor alpha was found to be overexpressed in the suprabasal layers of the transgenic epidermis. These findings suggest that autocrine mechanisms are involved in the development and maintenance of epidermal hyperplasia. Animals of both lines developed papillomas in skin sites exposed to mechanical irritation and wounding, suggesting that secondary events are necessary for progression to neoplasia. Collectively, these results provide new insights into the tumor promoter activities of human papillomavirus type 16 in epithelial cells in vivo.

Studies on in Vivo Induction of Cytotoxic T Lymphocyte Responses by Synthetic Peptides from E6 and E7 Oncoproteins of Human Papillomavirus Type 16

1995 ◽  
Vol 8 (3) ◽  
pp. 165-174 ◽  
Author(s):  
ASIS K. SARKAR ◽  
GUILLERMO TORTOLERO-LUNA ◽  
PRAMOD N. NEHETE ◽  
RALPH B. ARLINGHAUS ◽  
MICHELE FOLLEN MITCHELL ◽  
...  
Keyword(s):  
Human Papillomavirus ◽  
T Lymphocyte ◽  
Synthetic Peptides ◽  
Cytotoxic T Lymphocyte ◽  
Human Papillomavirus Type 16 ◽  
E6 And E7 Oncoproteins ◽  
E6 And E7 ◽  
Lymphocyte Responses ◽  
In Vivo Induction

scholarly journals Degradation of p53, Not Telomerase Activation, by E6 Is Required for Bypass of Crisis and Immortalization by Human Papillomavirus Type 16 E6/E7

2004 ◽  
Vol 78 (11) ◽  
pp. 5698-5706 ◽  
Author(s):  
H. R. McMurray ◽  
D. J. McCance
Keyword(s):  
Human Papillomavirus ◽  
Human Keratinocytes ◽  
Telomerase Activity ◽  
Transformation Process ◽  
Dominant Negative ◽  
Primary Human Keratinocytes ◽  
Telomere Shortening ◽  
Human Papillomavirus Type 16 ◽  
Tert Gene ◽  
E6 And E7

ABSTRACT Bypass of two arrest points is essential in the process of cellular immortalization, one of the components of the transformation process. Expression of human papillomavirus type 16 E6 and E7 together can escape both senescence and crisis, processes which normally limit the proliferative capacity of primary human keratinocytes. Crisis is thought to be mediated by telomere shortening. Because E6 stimulates telomerase activity and exogenous expression of the TERT gene with E7 can immortalize keratinocytes, this function is thought to be important for E6 to cooperate with E7 to bypass crisis. However, it has also been reported that E6 dissociates increased telomerase activity from maintenance of telomere length and that a dominant-negative p53 molecule can substitute for E6 in cooperative immortalization of keratinocytes with E7. Thus, to determine which functions of E6 are required to allow bypass of crisis and immortalization of keratinocytes with E7, immortalization assays were performed using specific mutants of E6, in tandem with E7. In these experiments, every clone expressing an E6 mutant capable of degrading p53 was able to bypass crisis and immortalize, regardless of telomerase induction. All clones containing E6 mutants incapable of degrading p53 died at crisis. These results suggest that the ability of E6 to induce degradation of p53 compensates for continued telomere shortening in E6/E7 cells and demonstrate that degradation of p53 is required for immortalization by E6/E7, while increased telomerase activity is dispensable.

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