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Beta-HPV 5 and 8 E6 promote p300 degradation by blocking AKT/p300 association.

ABSTRACT: The E6 oncoprotein from high-risk genus alpha human papillomaviruses (α-HPVs), such as HPV 16, has been well characterized with respect to the host-cell proteins it interacts with and corresponding signaling pathways that are disrupted due to these interactions. Less is known regarding the interacting partners of E6 from the genus beta papillomaviruses (β-HPVs); however, it is generally thought that β-HPV E6 proteins do not interact with many of the proteins known to bind to α-HPV E6. Here we identify p300 as a protein that interacts directly with E6 from both α- and β-HPV types. Importantly, this association appears much stronger with β-HPV types 5 and 8-E6 than with α-HPV type 16-E6 or β-HPV type 38-E6. We demonstrate that the enhanced association between 5/8-E6 and p300 leads to p300 degradation in a proteasomal-dependent but E6AP-independent manner. Rather, 5/8-E6 inhibit the association of AKT with p300, an event necessary to ensure p300 stability within the cell. Finally, we demonstrate that the decreased p300 protein levels concomitantly affect downstream signaling events, such as the expression of differentiation markers K1, K10 and Involucrin. Together, these results demonstrate a unique way in which β-HPV E6 proteins are able to affect host-cell signaling in a manner distinct from that of the α-HPVs.

SUBMITTER: Howie HL

PROVIDER: S-EPMC3161984 | biostudies-literature |

REPOSITORIES: biostudies-literature

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HPV E6 Impairs Translesion Synthesis by Blocking POLη Induction

Project description:Many DNA tumor viruses inhibit or repurpose host DNA repair pathways to evade viral defense mechanisms or promote their own replication. High risk genus α human papillomaviruses (α-HPVs) express two versatile oncogenes (α-HPV E6 and E7) that use both approaches simultaneously. To identify new interactions with DNA repair pathways, we conducted a computational analysis of gene expression in cervical cancer (CaCx) transcriptomic datasets and identified a frequent upregulation of translesion synthesis (TLS) genes. TLS polymerase genes, particularly the gene for POLη (POLH), did not follow this pattern. Characterization of α-HPV oncogene expressing cell lines and premalignant cervical tissue confirm these data. They also show that the increased TLS protein abundance come in response to nucleoside depletion. Primary and transformed cell lines to demonstrate that α-HPV E6 blocks POLη induction by degrading p53. Lack of POLη dooms the pathway, preventing it from facilitating tolerance of replication stress. Failed TLS results in replication fork stalling and collapse into deleterious double strand breaks in the DNA (DSBs). Consequently, cellular genome fidelity decreases in a manner consistent with the mutations that accumulate during CaCx progression. Alterations in TLS are determinants for the efficacy of the chemotherapeutics most often used to treat CaCx (cisplatin and carboplatin). Exogenous expression of POLη protected CaCx cells from cisplatin-associated toxicity/damage, effectively stabilizing their genome. TLS polymerase expression is also a prognostic factor in CaCx. Analysis of the cancer genome atlas database (TCGA) shows increased expression of these genes correlated with over a decade shorter median survival.

2020-05-01 | GSE145976 | GEO

High Risk α-HPV E6 Impairs Translesion Synthesis by Blocking POLη Induction.

Project description:High risk genus α human papillomaviruses (α-HPVs) express two versatile oncogenes (α-HPV E6 and E7) that cause cervical cancer (CaCx) by degrading tumor suppressor proteins (p53 and RB). α-HPV E7 also promotes replication stress and alters DNA damage responses (DDR). The translesion synthesis pathway (TLS) mitigates DNA damage by preventing replication stress from causing replication fork collapse. Computational analysis of gene expression in CaCx transcriptomic datasets identified a frequent increased expression of TLS genes. However, the essential TLS polymerases did not follow this pattern. These data were confirmed with in vitro and ex vivo systems. Further interrogation of TLS, using POLη as a representative TLS polymerase, demonstrated that α-HPV16 E6 blocks TLS polymerase induction by degrading p53. This doomed the pathway, leading to increased replication fork collapse and sensitivity to treatments that cause replication stress (e.g., UV and Cisplatin). This sensitivity could be overcome by the addition of exogenous POLη.

| S-EPMC7793514 | biostudies-literature

E6 proteins from high-risk HPV, low-risk HPV, and animal papillomaviruses activate the Wnt/β-catenin pathway through E6AP-dependent degradation of NHERF1.

Project description:High-risk human papillomavirus (HPV) E6 proteins associate with the cellular ubiquitin ligase E6-Associated Protein (E6AP), and then recruit both p53 and certain cellular PDZ proteins for ubiquitination and degradation by the proteasome. Low-risk HPV E6 proteins also associate with E6AP, yet fail to recruit p53 or PDZ proteins; their E6AP-dependent targets have so far been uncharacterized. We found a cellular PDZ protein called Na+/H+ Exchanger Regulatory Factor 1 (NHERF1) is targeted for degradation by both high and low-risk HPV E6 proteins as well as E6 proteins from diverse non-primate mammalian species. NHERF1 was degraded by E6 in a manner dependent upon E6AP ubiquitin ligase activity but independent of PDZ interactions. A novel structural domain of E6, independent of the p53 recognition domain, was necessary to associate with and degrade NHERF1, and the NHERF1 EB domain was required for E6-mediated degradation. Degradation of NHERF1 by E6 activated canonical Wnt/β-catenin signaling, a key pathway that regulates cell growth and proliferation. Expression levels of NHERF1 increased with increasing cell confluency. This is the first study in which a cellular protein has been identified that is targeted for degradation by both high and low-risk HPV E6 as well as E6 proteins from diverse animal papillomaviruses. This suggests that NHERF1 plays a role in regulating squamous epithelial growth and further suggests that the interaction of E6 proteins with NHERF1 could be a common therapeutic target for multiple papillomavirus types.

| S-EPMC6493770 | biostudies-literature

Structure of the E6/E6AP/p53 complex required for HPV-mediated degradation of p53.

Project description:The p53 pro-apoptotic tumour suppressor is mutated or functionally altered in most cancers. In epithelial tumours induced by 'high-risk' mucosal human papilloma viruses, including human cervical carcinoma and a growing number of head-and-neck cancers, p53 is degraded by the viral oncoprotein E6 (ref. 2). In this process, E6 binds to a short leucine (L)-rich LxxLL consensus sequence within the cellular ubiquitin ligase E6AP. Subsequently, the E6/E6AP heterodimer recruits and degrades p53 (ref. 4). Neither E6 nor E6AP are separately able to recruit p53 (refs 3, 5), and the precise mode of assembly of E6, E6AP and p53 is unknown. Here we solve the crystal structure of a ternary complex comprising full-length human papilloma virus type 16 (HPV-16) E6, the LxxLL motif of E6AP and the core domain of p53. The LxxLL motif of E6AP renders the conformation of E6 competent for interaction with p53 by structuring a p53-binding cleft on E6. Mutagenesis of critical positions at the E6-p53 interface disrupts p53 degradation. The E6-binding site of p53 is distal from previously described DNA- and protein-binding surfaces of the core domain. This suggests that, in principle, E6 may avoid competition with cellular factors by targeting both free and bound p53 molecules. The E6/E6AP/p53 complex represents a prototype of viral hijacking of both the ubiquitin-mediated protein degradation pathway and the p53 tumour suppressor pathway. The present structure provides a framework for the design of inhibitory therapeutic strategies against oncogenesis mediated by human papilloma virus.

| S-EPMC4853763 | biostudies-literature

Targeting HPV16 E6-p300 interaction reactivates p53 and inhibits the tumorigenicity of HPV-positive head and neck squamous cell carcinoma.

Project description:The incidence of human papillomavirus (HPV)-positive head and neck squamous cell carcinoma (HNSCC) has rapidly increased over the past 30 years, prompting the suggestion that an epidemic maybe on the horizon. Therefore, there is a clinical need to develop alternate therapeutic strategies to manage the growing number of HPV-positive HNSCC patients. High-risk HPV E6 inactivates p53 through two distinct mechanisms; association with E6AP to degrade p53 and association with p300 to block p300-mediated p53 acetylation and activation. In this study, we determined if targeting the E6-p300 interaction is an effective approach to reactivate p53 in HPV-positive HNSCC. Ectopic expression of the CH1 domain of p300 in HPV-positive HNSCC blocks the association between E6 and p300, increases total and acetylated p53 levels and enhances p53 transcriptional activity. Moreover, expression of p21, miR-34a and miR-200c are increased, demonstrating functional p53 reactivation. CH1 overexpression in HPV-positive HNSCC has a global anticancer effect resulting in a decrease in cell proliferation and clonogenic survival and an increase in apoptosis. The in vivo tumor-initiating ability of HPV-positive HNSCC is severely compromised with CH1 overexpression, in part through a reduction in the cancer-initiating cell population. A novel small-molecule CH1 inhibitor, CH1iB, reactivates p53 and potentiates the anticancer activity of cis-platinum in HPV-positive HNSCC cells. Our work shows that CH1-domain inhibitors represent a novel class of p53-reactivation therapeutics for managing HPV-positive HNSCC patients.

| S-EPMC3912227 | biostudies-literature

Docosahexaenoic acid induces the degradation of HPV E6/E7 oncoproteins by activating the ubiquitin-proteasome system.

Project description:The oncogenic human papillomavirus (HPV) E6/E7 proteins are essential for the onset and maintenance of HPV-associated malignancies. Here, we report that activation of the cellular ubiquitin-proteasome system (UPS) by the omega-3 fatty acid, docosahexaenoic acid (DHA), leads to proteasome-mediated degradation of E6/E7 viral proteins and the induction of apoptosis in HPV-infected cancer cells. The increases in UPS activity and degradation of E6/E7 oncoproteins were associated with DHA-induced overproduction of mitochondrial reactive oxygen species (ROS). Exogenous oxidative stress and pharmacological induction of mitochondrial ROS showed effects similar to those of DHA, and inhibition of ROS production abolished UPS activation, E6/E7 viral protein destabilization, and apoptosis. These findings identify a novel role for DHA in the regulation of UPS and viral proteins, and provide evidence for the use of DHA as a mechanistically unique anticancer agent for the chemoprevention and treatment of HPV-associated tumors.

| S-EPMC4260735 | biostudies-literature

HPV E6, E6AP and cervical cancer.

Project description:Every year, approximately 470,000 new cases of cervical cancer are diagnosed and approximately 230,000 women worldwide die of the disease, with the majority (approximately 80%) of these cases and deaths occurring in developing countries. Human papillomaviruses (HPVs) are the etiological agents in nearly all cases (99.7%) of cervical cancer, and the HPV E6 protein is one of two viral oncoproteins that is expressed in virtually all HPV-positive cancers. E6 hijacks a cellular ubiquitin ligase, E6AP, resulting in the ubiquitylation and degradation of the p53 tumor suppressor, as well as several other cellular proteins. While the recent introduction of prophylactic vaccines against specific HPV types offers great promise for prevention of cervical cancer, there remains a need for therapeutics. Biochemical characterization of E6 and E6AP has suggested approaches for interfering with the activities of these proteins that could be useful for this purpose. PUBLICATION HISTORY : Republished from Current BioData's Targeted Proteins database (TPdb; http://www.targetedproteinsdb.com).

| S-EPMC2582798 | biostudies-literature

p38 MAPK- and Akt-mediated p300 phosphorylation regulates its degradation to facilitate nucleotide excision repair.

Project description:Besides the primary histone acetyltransferase (HAT)-mediated chromatin remodeling function, co-transcriptional factor, p300, is also known to play a distinct role in DNA repair. However, the exact mechanism of p300 function in DNA repair has remained unclear and difficult to discern due to the phosphorylation and degradation of p300 in response to DNA damage. Here, we have demonstrated that p300 is only degraded in the presence of specific DNA lesions, which are the substrates of nucleotide excision repair (NER) pathway. In contrast, DNA double-strand breaks fail to degrade p300. Degradation is initiated by phosphorylation of p300 at serine 1834, which is catalyzed by the cooperative action of p38 mitogen-activated protein kinases and Akt kinases. In depth, functional analysis revealed that (i) p300 and CBP act redundantly in repairing ultraviolet (UV) lesions, (ii) the phosphorylation of p300 at S1834 is critical for efficient removal of UV-induced cyclobutane pyrimidine dimers and (iii) p300 is recruited to DNA damage sites located within heterochromatin. Taken together, we conclude that phosphorylated p300 initially acetylates histones to relax heterochromatin to allow damage recognition factors access to damage DNA. Thereupon, p300 is promptly degraded to allow the sequential recruitment of downstream repair proteins for successful execution of NER.

| S-EPMC3561975 | biostudies-literature

T Cell Receptor Immunotherapy Targeting HPV-16 E6 for HPV-Associated Cancers

Project description:Background: The National Cancer Institute (NCI) Surgery Branch has developed an experimental therapy for treating patients with cancer that involves taking white blood cells from the patient, growing them in the laboratory in large numbers, genetically modifying these specific cells with a type of virus (retrovirus) to attack only the tumor cells, and then giving the cells back to the patient. This type of therapy is called gene transfer. Researchers want to test this on human papilloma virus (HPV)-associated cancers. Objective: - The purpose of this study is to determine a safe number of these cells to infuse and to see if these particular tumor-fighting cells (Anti-HPV E6) can shrink tumors associated with HPV and test the toxicity of this treatment. Eligibility: - Adults age 18-66 with an HPV-16-associated cancer. Design: * Work up stage: Patients will be seen as an outpatient at the National Institutes of Health (NIH) clinical Center and undergo a history and physical examination, scans, x-rays, lab tests, and other tests as needed * Leukapheresis: If the patients meet all of the requirements for the study they will undergo leukapheresis to obtain white blood cells to make the anti HPV E6 cells. {Leukapheresis is a common procedure, which removes only the white blood cells from the patient.} * Treatment: Once their cells have grown, the patients will be admitted to the hospital for the conditioning chemotherapy, the anti HPV E6 cells and aldesleukin. They will stay in the hospital for about 4 weeks for the treatment. Follow up: Patients will return to the clinic for a physical exam, review of side effects, lab tests, and scans about every 1-3 months for the first year, and then every 6 months to 1 year as long as their tumors are shrinking. Follow up visits take up to 2 days.

| 2177506 | ecrin-mdr-crc

HPV-18 E6 Oncoprotein and Its Spliced Isoform E6*I Regulate the Wnt/β-Catenin Cell Signaling Pathway through the TCF-4 Transcriptional Factor.

Project description:The Wnt/β-catenin signaling pathway regulates cell proliferation and differentiation and its aberrant activation in cervical cancer has been described. Persistent infection with high risk human papillomavirus (HR-HPV) is the most important factor for the development of this neoplasia, since E6 and E7 viral oncoproteins alter cellular processes, promoting cervical cancer development. A role of HPV-16 E6 in Wnt/β-catenin signaling has been proposed, although the participation of HPV-18 E6 has not been previously studied. The aim of this work was to investigate the participation of HPV-18 E6 and E6*I, in the regulation of the Wnt/β-catenin signaling pathway. Here, we show that E6 proteins up-regulate TCF-4 transcriptional activity and promote overexpression of Wnt target genes. In addition, it was demonstrated that E6 and E6*I bind to the TCF-4 (T cell factor 4) and β-catenin, impacting TCF-4 stabilization. We found that both E6 and E6*I proteins interact with the promoter of Sp5, in vitro and in vivo. Moreover, although differences in TCF-4 transcriptional activation were found among E6 intratype variants, no changes were observed in the levels of regulated genes. Furthermore, our data support that E6 proteins cooperate with β-catenin to promote cell proliferation.

| S-EPMC6214013 | biostudies-literature

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