scholarly journals Cytoplasmic Poly(A) Binding Proteins Regulate Telomerase Activity and Cell Growth in Human Papillomavirus Type 16 E6-Expressing Keratinocytes

2010 ◽  
Vol 84 (24) ◽  
pp. 12934-12944 ◽  
Author(s):  
Rachel A. Katzenellenbogen ◽  
Portia Vliet-Gregg ◽  
Mei Xu ◽  
Denise A. Galloway
Keyword(s):  
Human Papillomavirus ◽  
Rna Processing ◽  
Posttranscriptional Regulation ◽  
Cellular Localization ◽  
Binding Proteins ◽  
Telomerase Activity ◽  
Htert Mrna ◽  
Hpv16 E6 ◽  
Hpv E6 ◽  
E6 And E7

ABSTRACT The high-risk human papillomavirus (HPV) E6 and E7 oncoproteins are critical to the immortalization of keratinocytes. HPV type 16 (HPV16) E6 interacts with endogenous proteins to activate hTERT, the catalytic subunit of telomerase, thus avoiding cellular senescence signals. NFX1-123, the longer splice variant of NFX1, interacts with HPV16 E6, as well as cytoplasmic poly(A) binding proteins 1 and 4 (PABPC1 and PABPC4). HPV16 E6 affects hTERT expression posttranscriptionally through NFX1-123, as NFX1-123 interacts with hTERT mRNA and stabilizes it, leading to greater telomerase activity. The PAM2 motif of NFX1-123, with which it binds PABPCs, is required for the posttranscriptional regulation of hTERT by HPV16 E6 and NFX1-123. There is increasing evidence that RNA and DNA viruses utilize RNA-processing proteins, and specifically PABPCs, in the normal virus life cycle, and there is also evidence that RNA-processing proteins are perturbed in cancers. Here, we show that PABPCs are critical in hTERT regulation by HPV16 E6. Although the amount and cellular localization of PABPCs were largely unchanged in cervical cancer cell lines with or without HPV16 and in human foreskin keratinocytes (HFKs) with or without HPV16 E6, knockdown of PABPCs decreased hTERT mRNA and telomerase activity and overexpression of PABPC4 increased these in HPV16 E6-expressing HFKs. In contrast, knockdown of PABPCs in C33A cells had no effect on hTERT mRNA or telomerase activity. Additionally, overexpression of PABPC4 and hTERT led to greater growth of cultured HPV16 E6-expressing HFKs. This is the first evidence that PABPCs have a targeted role in hTERT regulation leading to a growth advantage in cells expressing HPV16 E6.

scholarly journals NFX1-123 and Poly(A) Binding Proteins Synergistically Augment Activation of Telomerase in Human Papillomavirus Type 16 E6-Expressing Cells

2007 ◽  
Vol 81 (8) ◽  
pp. 3786-3796 ◽  
Author(s):  
Rachel A. Katzenellenbogen ◽  
Erin M. Egelkrout ◽  
Portia Vliet-Gregg ◽  
Lindy C. Gewin ◽  
Philip R. Gafken ◽  
...  
Keyword(s):  
Human Papillomavirus ◽  
Epithelial Cells ◽  
Binding Proteins ◽  
Telomerase Activity ◽  
Protein Domain ◽  
Mrna Levels ◽  
Hpv16 E6 ◽  
Hpv E6 ◽  
Protein Partners ◽  
Reporter Assays

ABSTRACT Overcoming senescence signals in somatic cells is critical to cellular immortalization and carcinogenesis. High-risk human papillomavirus (HPV) can immortalize epithelial cells in culture through degradation of the retinoblastoma protein by HPV E7 and activation of hTERT transcription, the catalytic subunit of telomerase, by the heterodimer HPV E6/E6-associated protein (E6AP). Recent work in our laboratory identified a novel repressor of hTERT transcription, NFX1-91, which is targeted for ubiquitin-mediated degradation by HPV type 16 (HPV16) E6/E6AP. In contrast, NFX1-123, a splice variant NFX1, increased expression from an hTERT promoter that was activated by HPV16 E6/E6AP. Here, we show that HPV16 E6 bound both NFX1-91 and NFX1-123 through the common central domain of NFX1 in the absence of E6AP. NFX1-123 positively regulated hTERT expression, as its knockdown decreased hTERT mRNA levels and telomerase activity and its overexpression increased telomerase activity. We identified new protein partners of NFX1-123, including several cytoplasmic poly(A) binding proteins (PABPCs) that interacted with NFX1-123 through its N-terminal PAM2 motif, a protein domain characteristic of other PABPC protein partners. Furthermore, NFX1-123 and PABPCs together had a synergistic stimulatory effect on hTERT-regulated reporter assays. The data suggest that NFX1-123 is integral to hTERT regulation in HPV16 E6-expressing epithelial cells and that the interaction between NFX1-123 and PABPCs is critical to hTERT activity.

scholarly journals NFX1-123 Increases hTERT Expression and Telomerase Activity Posttranscriptionally in Human Papillomavirus Type 16 E6 Keratinocytes

2009 ◽  
Vol 83 (13) ◽  
pp. 6446-6456 ◽  
Author(s):  
Rachel A. Katzenellenbogen ◽  
Portia Vliet-Gregg ◽  
Mei Xu ◽  
Denise A. Galloway
Keyword(s):  
Human Papillomavirus ◽  
Transcriptional Activation ◽  
Telomerase Activity ◽  
Mrna Levels ◽  
Htert Mrna ◽  
Cytoplasmic Protein ◽  
Nucleic Acid Binding ◽  
Htert Expression ◽  
Hpv16 E6

ABSTRACT High-risk human papillomavirus (HPV) E6 protein induces telomerase activity through transcriptional activation of hTERT, the catalytic subunit of telomerase. HPV type 16 (HPV16) E6 interacts with two splice variants of NFX1 to increase hTERT expression. NFX1-91 is a transcriptional repressor of hTERT that is polyubiquitinated and targeted for degradation by HPV16 E6 in concert with E6-associated protein. We previously showed that NFX1-123 augments hTERT expression through binding to cytoplasmic poly(A) binding proteins (PABPCs). In this study, we determined that unlike NFX1-91, NFX1-123 is a cytoplasmic protein that colocalized with PABPCs but does not shuttle with PABPCs between the nucleus and cytoplasm. NFX1-123 requires both its PAM2 motif, with which it binds PABPCs, and its R3H domain, which has putative nucleic acid binding capabilities, to increase hTERT mRNA levels and telomerase activity in keratinocytes expressing HPV16 E6. In keratinocytes expressing HPV16 E6 and overexpressing NFX1-123, there was increased protein expression from in vitro-transcribed RNA fused with the 5′ untranslated region (5′ UTR) of hTERT. This posttranscriptional increase in expression required the PAM2 motif and R3H domain of NFX1-123 as well as the coexpression of HPV16 E6. NFX1-123 bound endogenous hTERT mRNA and increased its stability in HPV16 E6-expressing human foreskin keratinocytes, and NFX1-123 increased the stability of in vitro-transcribed RNA fused with the 5′ UTR of hTERT. Together, these studies describe the first evidence of posttranscriptional regulation of hTERT, through the direct interaction of the cytoplasmic protein NFX1-123 with hTERT mRNA, in HPV16 E6-expressing keratinocytes.

scholarly journals Identification of High-Risk Human Papillomavirus DNA, p16 and E6/E7 Oncoproteins in Laryngeal and Hypopharyngeal Squamous Cell Carcinomas

Viruses ◽  
2021 ◽  
Vol 13 (6) ◽  
pp. 1008
Author(s):  
Andrejs Lifsics ◽  
Valerija Groma ◽  
Maksims Cistjakovs ◽  
Sandra Skuja ◽  
Renars Deksnis ◽  
...  
Keyword(s):  
Human Papillomavirus ◽  
High Risk ◽  
Squamous Cell ◽  
Surrogate Marker ◽  
Hpv Infection ◽  
Hpv16 E6 ◽  
Hpv Dna ◽  
Molecular Virology ◽  
Hpv E6 ◽  
E6 And E7

Human papillomavirus (HPV) was proven to play a significant role in cancer development in the oropharynx. However, its role in the development of laryngeal (LSCC) and hypopharyngeal squamous cell carcinoma (HPSCC) remains to be clarified. High-risk HPV (HR-HPV) viral proteins E6 and E7 are considered to be pertinent to HPV-related carcinogenesis. Hence, our aim was to estimate LSCC and HPSCC for HR-HPV DNA, p16, and E6/E7 oncoprotein status by using molecular virology and immunohistochemistry methods. The prevalence of HPV16 infection was 22/41 (53.7%) and 20/31 (64.5%) for LSCC and HPSCC, accordingly. The majority of HPV16+ tumor samples were stage III or IV. In most samples, the presence of either HPV16 E6 or HPV16 E7 viral protein in dysplastic or tumor cells was confirmed using immunohistochemistry. Our results suggest a high prevalence of HPV16 as a primary HR-HPV type in LSCC and HPSCC. The lack of HPV E6/E7 oncoproteins in some tumor samples may suggest either the absence of viral integration or the presence of other mechanisms of tumorigenesis. The utilization of p16 IHC as a surrogate marker of HR-HPV infection is impractical in LSCC and HPSCC.

scholarly journals Intrabodies targeting human papillomavirus 16 E6 and E7 oncoproteins for therapy of established HPV-associated tumors

2021 ◽  
Vol 40 (1) ◽  
Author(s):  
Francesca Paolini ◽  
Carla Amici ◽  
Mariantonia Carosi ◽  
Claudia Bonomo ◽  
Paola Di Bonito ◽  
...  
Keyword(s):  
Human Papillomavirus ◽  
Antitumor Activity ◽  
Tumor Growth ◽  
Tumor Progression ◽  
Cellular Transformation ◽  
Neoplastic Progression ◽  
Single Chain ◽  
Hpv16 E6 ◽  
Associated Lesions ◽  
E6 And E7

Abstract Background The oncogenic activity of the high risk human papillomavirus type 16 (HPV16) is fully dependent on the E6 and E7 viral oncoproteins produced during viral infection. The oncoproteins interfere with cellular homeostasis by promoting proliferation, inhibiting apoptosis and blocking epithelial differentiation, driving the infected cells towards neoplastic progression. The causal relationship between expression of E6/E7 and cellular transformation allows inhibiting the oncogenic process by hindering the activity of the two oncoproteins. We previously developed and characterized some antibodies in single-chain format (scFvs) against the HPV16 E6 and E7 proteins, and demonstrated both in vitro and in vivo their antitumor activity consisting of protective efficacy against tumor progression of HPV16-positive cells. Methods Envisioning clinical application of the best characterized anti-HPV16 E6 and –HPV16 E7 scFvs, we verified their activity in the therapeutic setting, on already implanted tumors. Recombinant plasmids expressing the anti-HPV16 E6 scFvI7 with nuclear targeting sequence, or the anti-HPV16 E7 scFv43M2 with endoplasmic reticulum targeting sequence were delivered by injection followed by electroporation to three different preclinical models using C57/BL6 mice, and their effect on tumor growth was investigated. In the first model, the HPV16+ TC-1 Luc cells were used to implant tumors in mice, and tumor growth was measured by luciferase activity; in the second model, a fourfold number of TC-1 cells was used to obtain more aggressively growing tumors; in the third model, the HPV16+ C3 cells where used to rise tumors in mice. To highlight the scFv possible mechanism of action, H&E and caspase-3 staining of tumor section were performed. Results We showed that both the anti-HPV16 E6 and HPV16 E7 scFvs tested were efficacious in delaying tumor progression in the three experimental models and that their antitumor activity seems to rely on driving tumor cells towards the apoptotic pathway. Conclusion Based on our study, two scFvs have been identified that could represent a safe and effective treatment for the therapy of HPV16-associated lesions. The mechanism underlying the scFv effectiveness appears to be leading cells towards death by apoptosis. Furthermore, the validity of electroporation, a methodology allowed for human treatment, to deliver scFvs to tumors was confirmed.

scholarly journals Human Papillomavirus E6 Proteins Mediate Resistance to Interferon-Induced Growth Arrest through Inhibition of p53 Acetylation

2007 ◽  
Vol 81 (23) ◽  
pp. 12740-12747 ◽  
Author(s):  
Christy Hebner ◽  
Melanie Beglin ◽  
Laimonis A. Laimins
Keyword(s):  
Human Papillomavirus ◽  
Human Fibroblasts ◽  
Antiviral Agents ◽  
Growth Arrest ◽  
Physiological Role ◽  
Human Keratinocytes ◽  
Hpv E6 ◽  
E6 And E7 ◽  
E7 Proteins ◽  
Mutant Forms

ABSTRACT The high-risk human papillomavirus (HPV) E6 and E7 proteins act cooperatively to mediate multiple activities in viral pathogenesis. For instance, E7 acts to increase p53 levels while E6 accelerates its rate of turnover through the binding of the cellular ubiquitin ligase E6AP. Interferons are important antiviral agents that modulate both the initial and persistent phases of viral infection. The expression of HPV type 16 E7 was found to sensitize keratinocytes to the growth-inhibitory effects of interferon, while coexpression of E6 abrogates this inhibition. Treatment of E7-expressing cells with interferon ultimately resulted in cellular senescence through a process that is dependent upon acetylation of p53 by p300/CBP at lysine 382. Cells expressing mutant forms of E6 that are unable to bind p300/CBP or bind p53 failed to block acetylation of p53 at lysine 382 and were sensitive to growth arrest by interferon. In contrast, mutant forms of E6 that are unable to bind E6AP remain resistant to the effects of interferon, demonstrating that the absolute levels of p53 are not the major determinants of this activity. Finally, p53 acetylation at lysine 382 was found not to be an essential determinant of other types of senescence such as that induced by overexpression of Ras in human fibroblasts. This study identifies an important physiological role for E6 binding to p300/CBP in blocking growth arrest of human keratinocytes in the presence of interferon and so contributes to the persistence of HPV-infected cells.

scholarly journals The Global Transcriptional Effects of the Human Papillomavirus E6 Protein in Cervical Carcinoma Cell Lines Are Mediated by the E6AP Ubiquitin Ligase

2005 ◽  
Vol 79 (6) ◽  
pp. 3737-3747 ◽  
Author(s):  
Melissa L. Kelley ◽  
Kerri E. Keiger ◽  
Chan Jae Lee ◽  
Jon M. Huibregtse
Keyword(s):  
Human Papillomavirus ◽  
Cell Lines ◽  
Ubiquitin Ligase ◽  
Telomerase Activity ◽  
Transcriptional Program ◽  
Hpv E6 ◽  
Amplification Protocol ◽  
Independent Functions ◽  
Interfering Rna ◽  
E6 Protein

ABSTRACT The function of the human papillomavirus (HPV) E6 protein that is most clearly linked to carcinogenesis is the targeted degradation of p53, which is dependent on the E6AP ubiquitin ligase. Additional functions have been attributed to E6, including the stimulation of telomerase activity and the targeted degradation of other cellular proteins, but in most cases it is unclear whether these activities are also E6AP dependent. While E6 clearly influences the transcriptional program of HPV-positive cell lines through the inactivation of p53, it has been shown that at least a subset of its p53-independent functions are also reflected in the transcriptional program. For this study, we have determined the extent to which E6AP is involved in mediating the set of E6 functions that impact on the global transcriptional program of HPV-positive cell lines. The transcriptional profiles of ∼31,000 genes were characterized for three cell lines (HeLa, Caski, and SiHa cells) after small interfering RNA (siRNA)-mediated silencing of E6 or E6AP. We found that E6 and E6AP siRNAs elicited nearly identical alterations in the transcriptional profile of each cell line. Some of the expression alterations were apparent secondary effects of p53 stabilization, while the basis of most other changes was not reconcilable with previously proposed E6 functions. While expression changes of the TERT gene (telomerase catalytic subunit) were not revealed by the array, telomerase repeat amplification protocol assays showed that both E6 and E6AP knockouts resulted in a suppression of telomerase activity. Together, these results suggest that E6AP mediates a broad spectrum of E6 functions, including virtually all functions that impact on the transcriptional program of HPV-positive cell lines.

scholarly journals The High-Risk Human Papillomavirus Type 16 E6 Counters the GAP Function of E6TP1 toward Small Rap G Proteins

2003 ◽  
Vol 77 (2) ◽  
pp. 1614-1620 ◽  
Author(s):  
Latika Singh ◽  
Qingshen Gao ◽  
Ajay Kumar ◽  
Takaya Gotoh ◽  
David E. Wazer ◽  
...  
Keyword(s):  
Human Papillomavirus ◽  
High Risk ◽  
G Protein ◽  
Mutational Analysis ◽  
Protein Signaling ◽  
Hpv16 E6 ◽  
Human Papillomavirus Type 16 ◽  
Hpv E6 ◽  
Small G Protein ◽  
Transforming Activity

ABSTRACT We have recently identified E6TP1 (E6-targeted protein 1) as a novel high-risk human papillomavirus type 16 (HPV16) E6-binding protein. Importantly, mutational analysis of E6 revealed a strong correlation between the transforming activity and its abilities to bind and target E6TP1 for ubiquitin-mediated degradation. As a region within E6TP1 has high homology with GAP domains of known and putative Rap GTPase-activating proteins (GAPs), these results raised the possibility that HPV E6 may alter the Rap small-G-protein signaling pathway. Using two different approaches, we now demonstrate that human E6TP1 exhibits GAP activity for Rap1 and Rap2, confirming recent findings that a closely related rat homologue exhibits Rap-specific GAP activity. Using mutational analysis, we localize the GAP activity to residues 240 to 945 of E6TP1. Significantly, we demonstrate that coexpression of HPV16 E6, by promoting the degradation of E6TP1, enhances the GTP loading of Rap. These results support a role of Rap small-G-protein pathway in E6-mediated oncogenesis.

scholarly journals NFX1 Plays a Role in Human Papillomavirus Type 16 E6 Activation of NFκB Activity

2010 ◽  
Vol 84 (21) ◽  
pp. 11461-11469 ◽  
Author(s):  
Mei Xu ◽  
Rachel A. Katzenellenbogen ◽  
Carla Grandori ◽  
Denise A. Galloway
Keyword(s):  
Human Papillomavirus ◽  
Human Telomerase Reverse Transcriptase ◽  
Hpv16 E6 ◽  
Regulatory Pathways ◽  
Cellular Processes ◽  
Hpv E6 ◽  
Host Cell Interactions ◽  
Nfκb Pathway ◽  
Human Telomerase ◽  
Dual Regulator

ABSTRACT High-risk human papillomavirus (HR HPV) requires differentiating epithelial cells to continue to divide in order to replicate the viral DNA. To achieve this, HPV perturbs several regulatory pathways, including cellular apoptosis and senescence signals. HPV E6 has been identified as a regulator of the NFκB signaling pathway, a pathway important in many cellular processes, as well as regulation of virus-host cell interactions. We report here that NFX1-91, an endogenously expressed transcriptional regulator of human telomerase reverse transcriptase (hTERT) that is targeted by HPV type 16 (HPV16) E6/E6-associated protein (E6AP) for degradation, is also critical for regulation of the NFκB pathway by HPV16 E6. Microarray analysis revealed induction of NFκB-responsive genes and reduction of NFκB inhibitors with knockdown of NFX1-91. Knockdown of NFX1-91 induced downregulation of p105, an NFκB inhibitor in both primary human foreskin keratinocytes (HFKs) and HCT116 cells. Chromatin immunoprecipitation assays further confirmed that NFX1-91 bound to the p105 promoter and upregulated its expression. Similarly, in HPV16 E6-positive cells, reduction of p105 expression was observed, paralleling knockdown of NFX1-91 expression. Overall, our data suggest a mechanism for HPV16 E6 activation of the NFκB pathway through NFX1-91. Also, it provides evidence that NFX1-91 can function as a dual regulator, not only a transcriptional repressor, but also a transcriptional activator, when bound to DNA.

scholarly journals Upregulation of PIR gene expression induced by human papillomavirus E6 and E7 in epithelial oral and cervical cells

Open Biology ◽  
2017 ◽  
Vol 7 (11) ◽  
pp. 170111 ◽  
Author(s):  
Diego Carrillo ◽  
Juan P. Muñoz ◽  
Hernán Huerta ◽  
Gabriel Leal ◽  
Alejandro Corvalán ◽  
...  
Keyword(s):  
Gene Expression ◽  
Human Papillomavirus ◽  
Dna Microarrays ◽  
Epithelial Mesenchymal Transition ◽  
Dependent Manner ◽  
Mesenchymal Transition ◽  
Hpv E6 ◽  
E6 And E7 Oncoproteins ◽  
E6 And E7 ◽  
Oral Cells

The hallmark of high-risk human papillomavirus (HR-HPV)-related carcinogenesis is E6 and E7 oncogene overexpression. The aim of this work was to characterize epithelial oral and cervical cancer cells that express HR-HPV E6 and E7 oncoproteins. Transcriptomic assay using DNA microarrays revealed that PIR gene expression was detected in oral cells in an HR-HPV E6/E7-dependent manner. In addition, PIR was overexpressed in HPV-positive SiHa and Ca Ski cells, whereas it was undetectable in HPV-negative C33A cells. The PIR expression was dependent on functional HR-HPV E6 and E7 oncoproteins even though the E7 oncoprotein had higher activity to induce PIR overexpression in comparison with E6. In addition, using an siRNA for PIR silencing in oral cells ectopically expressing HR-HPV E6/E7, there was a significant increase in E-cadherin transcripts and a decrease in Vimentin, Slug, Zeb and Snail transcripts, suggesting that HR-HPV-induced PIR overexpression is involved in epithelial–mesenchymal transition. Furthermore, migration of PIR-silenced cells was significantly decreased. Finally, using inhibitors of some specific pathways, it was found that EGFR/ERK and PI3 K/AKT signalling pathways are important for E7-mediated PIR overexpression. It can be concluded that PIR gene expression is highly dependent on the expression of HR-HPV oncoproteins and is important for EMT regulation.

scholarly journals MicroRNA 203 Expression in Keratinocytes Is Dependent on Regulation of p53 Levels by E6

2010 ◽  
Vol 84 (20) ◽  
pp. 10644-10652 ◽  
Author(s):  
Declan J. McKenna ◽  
Simon S. McDade ◽  
Daksha Patel ◽  
Dennis J. McCance
Keyword(s):  
Dna Damage ◽  
Human Papillomavirus ◽  
Cell Biology ◽  
Viral Oncoprotein ◽  
Hpv16 E6 ◽  
Human Papillomavirus Type 16 ◽  
Proliferation And Differentiation ◽  
Short Hairpin ◽  
E6 And E7 ◽  
Short Hairpin Rnas

ABSTRACT A screen of microRNA (miRNA) expression following differentiation in human foreskin keratinocytes (HFKs) identified changes in several miRNAs, including miRNA 203 (miR-203), which has previously been shown to play an important role in epithelial cell biology by regulating p63 levels. We investigated how expression of human papillomavirus type 16 (HPV16) oncoproteins E6 and E7 affected miR-203 expression during proliferation and differentiation of HFKs. We demonstrated that miR-203 expression is reduced in HFKs where p53 function is compromised, either by the viral oncoprotein E6 or by knockout of p53 using short hairpin RNAs (p53i). We show that the induction of miR-203 observed during calcium-induced differentiation of HFKs is significantly reduced in HFKs expressing E6 and in p53i HFKs. Induction of miR-203 in response to DNA damage is also reduced in the absence of p53. We report that proliferation of HFKs is dependent on the level of miR-203 expression and that overexpression of miR-203 can reduce overproliferation in E6/E7-expressing and p53i HFKs. In summary, these results indicate that expression of miR-203 is dependent on p53, which may explain how expression of HPV16 E6 can disrupt the balance between proliferation and differentiation, as well as the response to DNA damage, in keratinocytes.

Sign in / Sign up

Export Citation Format

Share Document