scholarly journals E6 Proteins from Multiple Human Betapapillomavirus Types Degrade Bak and Protect Keratinocytes from Apoptosis after UVB Irradiation

2008 ◽  
Vol 82 (21) ◽  
pp. 10408-10417 ◽  
Author(s):  
Michael P. Underbrink ◽  
Heather L. Howie ◽  
Kristin M. Bedard ◽  
Jennifer I. Koop ◽  
Denise A. Galloway
Keyword(s):  
Ubiquitin Ligase ◽  
E3 Ubiquitin Ligase ◽  
Intrinsic Apoptotic Pathway ◽  
Uv Damage ◽  
Uv Treatment ◽  
Apoptotic Pathway ◽  
Hpv16 E6 ◽  
Hpv E6 ◽  
Hpv Types ◽  
E6 Protein

ABSTRACT Human papillomavirus (HPV) types from the beta genus (beta-HPVs) have been implicated in the development of skin cancer. A potentially important aspect of their carcinogenic role is the ability of the E6 protein to degrade the proapoptotic family member Bak, which gives cells the ability to survive UV damage. However, it is unknown if the ability to degrade Bak is limited to certain beta-HPV types or whether E6 expression in keratinocytes affects other proteins important for apoptosis signaling. We tested the abilities of E6 proteins from several representative members of the beta-HPVs to degrade Bak and protect UV-treated keratinocytes from apoptosis. The E6 proteins of the beta-HPV type 5 (HPV5), -8, -20, -22, -38, -76, -92, and -96, as well as the alpha genus HPV HPV16, all degraded Bak or prevented its accumulation following UV treatment but did not degrade Bak constitutively. In addition, when tested using HPV16 E6 (16E6) and 8E6 as representative E6 proteins from the alpha and beta genera, respectively, Bak degradation was dependent on the E3 ubiquitin ligase, E6AP. Other important regulators of apoptotic signaling were examined and found to be unperturbed by the expression of the beta-HPV E6 proteins. Importantly, the expression of beta-HPV E6 proteins protected keratinocytes from apoptosis to the same extent as 16E6-expressing cells. In conclusion, several of the beta-HPV types possess the ability to protect UV-treated keratinocytes from apoptosis by reducing levels of Bak in those cells, thus blocking the intrinsic apoptotic pathway.

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 E6 Oncoproteins of High-Risk Papillomaviruses Bind to a Novel Putative GAP Protein, E6TP1, and Target It for Degradation

1999 ◽  
Vol 19 (1) ◽  
pp. 733-744 ◽  
Author(s):  
Qingshen Gao ◽  
Seetha Srinivasan ◽  
Sarah N. Boyer ◽  
David E. Wazer ◽  
Vimla Band
Keyword(s):  
High Risk ◽  
P53 Protein ◽  
Single Gene ◽  
Human Papillomaviruses ◽  
Dominant Negative ◽  
Hpv16 E6 ◽  
Hpv E6 ◽  
E6 Oncoprotein ◽  
E6 Protein

ABSTRACT The high-risk human papillomaviruses (HPVs) are associated with carcinomas of the cervix and other genital tumors. Previous studies have identified two viral oncoproteins, E6 and E7, which are expressed in the majority of HPV-associated carcinomas. The ability of high-risk HPV E6 protein to immortalize human mammary epithelial cells (MECs) has provided a single-gene model to study the mechanisms of E6-induced oncogenic transformation. In this system, the E6 protein targets the p53 tumor suppressor protein for degradation, and mutational analyses have shown that E6-induced degradation of p53 protein is required for MEC immortalization. However, the inability of most dominant-negative p53 mutants to induce efficient immortalization of MECs suggests the existence of additional targets of the HPV E6 oncoprotein. Using the yeast two-hybrid system, we have isolated a novel E6-binding protein. This polypeptide, designated E6TP1 (E6-targeted protein 1), exhibits high homology to GTPase-activating proteins for Rap, including SPA-1, tuberin, and Rap1GAP. The mRNA for E6TP1 is widely expressed in tissues and in vitro-cultured cell lines. The gene for E6TP1 localizes to chromosome 14q23.2-14q24.3 within a locus that has been shown to undergo loss of heterozygosity in malignant meningiomas. Importantly, E6TP1 is targeted for degradation by the high-risk but not the low-risk HPV E6 proteins both in vitro and in vivo. Furthermore, the immortalization-competent but not the immortalization-incompetent HPV16 E6 mutants target the E6TP1 protein for degradation. Our results identify a novel target for the E6 oncoprotein and provide a potential link between HPV E6 oncogenesis and alteration of a small G protein signaling pathway.

scholarly journals E3 ubiquitin ligase E6AP-mediated TSC2 turnover in the presence and absence of HPV16 E6

2008 ◽  
Vol 13 (3) ◽  
pp. 285-294 ◽  
Author(s):  
Li Zheng ◽  
Huirong Ding ◽  
Zheming Lu ◽  
Yong Li ◽  
Yaqi Pan ◽  
...  
Keyword(s):  
Ubiquitin Ligase ◽  
E3 Ubiquitin Ligase ◽  
Hpv16 E6 ◽  
Presence And Absence

scholarly journals β-HPV 8E6 Attenuates ATM and ATR Signaling in Response to UV Damage

2019 ◽  
Author(s):  
Jazmine A. Snow ◽  
Vaibhav Murthy ◽  
Dalton Dacus ◽  
Changkun Hu ◽  
Nicholas A. Wallace
Keyword(s):  
Host Cells ◽  
Uv Damage ◽  
Downstream Signaling ◽  
Hpv E6 ◽  
Cycle Arrest ◽  
Non Melanoma Skin Cancer ◽  
High Prevalence ◽  
E6 Protein ◽  
The Impact

Given the high prevalence of cutaneous genus beta human papillomavirus (β-HPV) infections, it is important to understand how they are manipulating their host cells. This is particularly true for cellular responses to UV damage, since our skin is continually exposed to UV. The E6 protein from β-HPV (β-HPV E6) decreases the abundance of two essential UV-repair kinases (ATM and ATR). Since β-HPV E6 reduces their availability, the impact on downstream signaling events has been uncertain. We demonstrate that β-HPV E6 decreases ATM and ATR activation. This inhibition extended to XPA, an ATR target necessary for UV repair, lowering both its phosphorylation and accumulation. β-HPV E6 hinders POLη phosphorylation and foci formation, critical steps in translesion synthesis. ATM’s phosphorylation of BRCA1 is also attenuated by β-HPV E6. However, β-HPV E6’s hindrance of ATM/ATR signaling during UV-associated cell cycle arrest was incomplete. While there was less phosphorylation of immediate downstream targets (CHK1), events further down the cascade were not decreased. These observations are consistent with β-HPV infections making UV radiation more deleterious and support the proposed role of β-HPV in early stages of non-melanoma skin cancer development.

scholarly journals β-HPV 8E6 Attenuates ATM and ATR Signaling in Response to UV Damage

Pathogens ◽  
2019 ◽  
Vol 8 (4) ◽  
pp. 267 ◽  
Author(s):  
Jazmine A. Snow ◽  
Vaibhav Murthy ◽  
Dalton Dacus ◽  
Changkun Hu ◽  
Nicholas A. Wallace
Keyword(s):  
Cellular Responses ◽  
Host Cells ◽  
Uv Damage ◽  
Downstream Signaling ◽  
Hpv E6 ◽  
High Prevalence ◽  
Functional Consequences ◽  
E6 Protein ◽  
The Impact ◽  
Atr Activation

Given the high prevalence of cutaneous genus beta human papillomavirus (β-HPV) infections, it is important to understand how they manipulate their host cells. This is particularly true for cellular responses to UV damage, since our skin is continually exposed to UV. The E6 protein from β-genus HPV (β-HPV E6) decreases the abundance of two essential UV-repair kinases (ATM and ATR). Although β-HPV E6 reduces their availability, the impact on downstream signaling events is unclear. We demonstrate that β-HPV E6 decreases ATM and ATR activation. This inhibition extended to XPA, an ATR target necessary for UV repair, lowering both its phosphorylation and accumulation. β-HPV E6 also hindered POLη accumulation and foci formation, critical steps in translesion synthesis. ATM’s phosphorylation of BRCA1 is also attenuated by β-HPV E6. While there was a striking decrease in phosphorylation of direct ATM/ATR targets, events further down the cascade were not reduced. In summary, despite being incomplete, β-HPV 8E6’s hindrance of ATM/ATR has functional consequences.

Author response for "TAM receptors attenuate murine NK cell responses via E3 ubiquitin ligase Cbl‐b"

2019 ◽  
Author(s):  
Leilani M. Chirino ◽  
Suresh Kumar ◽  
Mariko Okumura ◽  
David E. Sterner ◽  
Michael Mattern ◽  
...  
Keyword(s):  
Ubiquitin Ligase ◽  
Nk Cell ◽  
E3 Ubiquitin Ligase ◽  
Author Response ◽  
Cell Responses ◽  
Tam Receptors

Activation of the intrinsic-apoptotic pathway in LNCaP prostate cancer cells by genistein- topotecan combination treatments

2013 ◽  
Vol 3 (3) ◽  
pp. 66 ◽  
Author(s):  
Vanessa Hörmann ◽  
Sivanesan Dhandayuthapani ◽  
James Kumi-Diaka ◽  
Appu Rathinavelu
Keyword(s):  
Prostate Cancer ◽  
Cell Death ◽  
Cancer Cells ◽  
Apoptotic Cell ◽  
Treatment Options ◽  
Attractive Alternative ◽  
Intrinsic Apoptotic Pathway ◽  
Prostate Cancer Cells ◽  
Apoptotic Pathway ◽  
Combination Treatments

Background: Prostate cancer is the second most common cancer in American men. The development of alternative preventative and/or treatment options utilizing a combination of phytochemicals and chemotherapeutic drugs could be an attractive alternative compared to conventional carcinoma treatments. Genistein isoflavone is the primary dietary phytochemical found in soy and has demonstrated anti-tumor activities in LNCaP prostate cancer cells. Topotecan Hydrochloride (Hycamtin) is an FDA-approved chemotherapy for secondary treatment of lung, ovarian and cervical cancers. The purpose of this study was to detail the potential activation of the intrinsic apoptotic pathway in LNCaP prostate cancer cells through genistein-topotecan combination treatments. Methods: LNCaP cells were cultured in complete RPMI medium in a monolayer (70-80% confluency) at 37ºC and 5% CO2. Treatment consisted of single and combination groups of genistein and topotecan for 24 hours. The treated cells were assayed for i) growth inhibition through trypan blue exclusion assay and microphotography, ii) classification of cellular death through acridine/ ethidium bromide fluorescent staining, and iii) activation of the intrinsic apoptotic pathway through Jc-1: mitochondrial membrane potential assay, cytochrome c release and Bcl-2 protein expression.Results: The overall data indicated that genistein-topotecan combination was significantly more efficacious in reducing the prostate carcinoma’s viability compared to the single treatment options. In all treatment groups, cell death occurred primarily through the activation of the intrinsic apoptotic pathway.Conclusion: The combination of topotecan and genistein has the potential to lead to treatment options with equal therapeutic efficiency as traditional chemo- and radiation therapies, but lower cell cytotoxicity and fewer side effects in patients. Key words: topotecan; genistein; intrinsic apoptotic cell death

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