Dataset Information

High-Risk Human Papillomavirus E7 Proteins Target PTPN14 for Degradation.

ABSTRACT: The major transformation activity of the high-risk human papillomaviruses (HPV) is associated with the E7 oncoprotein. The interaction of HPV E7 with retinoblastoma family proteins is important for several E7 activities; however, this interaction does not fully account for the high-risk E7-specific cellular immortalization and transformation activities. We have determined that the cellular non-receptor protein tyrosine phosphatase PTPN14 interacts with HPV E7 from many genus alpha and beta HPV types. We find that high-risk genus alpha HPV E7, but not low-risk genus alpha or beta HPV E7, is necessary and sufficient to reduce the steady-state level of PTPN14 in cells. High-risk E7 proteins target PTPN14 for proteasome-mediated degradation, which requires the ubiquitin ligase UBR4, and PTPN14 is degraded by the proteasome in HPV-positive cervical cancer cell lines. Residues in the C terminus of E7 interact with the C-terminal phosphatase domain of PTPN14, and interference with the E7-PTPN14 interaction restores PTPN14 levels in cells. Finally, PTPN14 degradation correlates with the retinoblastoma-independent transforming activity of high-risk HPV E7. High-risk human papillomaviruses (HPV) are the cause of cervical cancer, some other anogenital cancers, and a growing fraction of oropharyngeal carcinomas. The high-risk HPV E6 and E7 oncoproteins enable these viruses to cause cancer, and the mechanistic basis of their carcinogenic activity has been the subject of intense study. The high-risk E7 oncoprotein is especially important in the immortalization and transformation of human cells, which makes it a central component of HPV-associated cancer development. E7 oncoproteins interact with retinoblastoma family proteins, but for several decades, it has been recognized that high-risk HPV E7 oncoproteins have additional cancer-associated activities. We have determined that high-risk E7 proteins target the proteolysis of the cellular protein tyrosine phosphatase PTPN14 and find that this activity is correlated with the retinoblastoma-independent transforming activity of E7.

SUBMITTER: White EA

PROVIDER: S-EPMC5030362 | biostudies-literature | 2016 Sep

REPOSITORIES: biostudies-literature

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High-Risk Human Papillomavirus E7 Proteins Target PTPN14 for Degradation.

White Elizabeth A EA Münger Karl K Howley Peter M PM

mBio 20160920 5

<h4>Unlabelled</h4>The major transformation activity of the high-risk human papillomaviruses (HPV) is associated with the E7 oncoprotein. The interaction of HPV E7 with retinoblastoma family proteins is important for several E7 activities; however, this interaction does not fully account for the high-risk E7-specific cellular immortalization and transformation activities. We have determined that the cellular non-receptor protein tyrosine phosphatase PTPN14 interacts with HPV E7 from many genus a ...[more]

PMID: 27651363

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Project description:The human papillomavirus (HPV) E7 oncoprotein is a primary driver of HPV-mediated carcinogenesis. The E7 proteins from diverse HPVs bind to the host cellular nonreceptor protein tyrosine phosphatase type 14 (PTPN14) and direct it for degradation through the activity of the E7-associated host E3 ubiquitin ligase UBR4. Here, we show that a highly conserved arginine residue in the C-terminal domain of diverse HPV E7 mediates the interaction with PTPN14. We found that disruption of PTPN14 binding through mutation of the C-terminal arginine did not impact the ability of several high-risk HPV E7 proteins to bind and degrade the retinoblastoma tumor suppressor or activate E2F target gene expression. HPVs infect human keratinocytes, and we previously reported that both PTPN14 degradation by HPV16 E7 and PTPN14 CRISPR knockout repress keratinocyte differentiation-related genes. Now, we have found that blocking PTPN14 binding through mutation of the conserved C-terminal arginine rendered both HPV16 and HPV18 E7 unable to repress differentiation-related gene expression. We then confirmed that the HPV18 E7 variant that could not bind PTPN14 was also impaired in repressing differentiation when expressed from the complete HPV18 genome. Finally, we found that the ability of HPV18 E7 to extend the life span of primary human keratinocytes required PTPN14 binding. CRISPR/Cas9 knockout of PTPN14 rescued keratinocyte life span extension in the presence of the PTPN14 binding-deficient HPV18 E7 variant. These results support the model that PTPN14 degradation by high-risk HPV E7 leads to repression of differentiation and contributes to its carcinogenic activity.IMPORTANCE The E7 oncoprotein is a primary driver of HPV-mediated carcinogenesis. HPV E7 binds the putative tumor suppressor PTPN14 and targets it for degradation using the ubiquitin ligase UBR4. PTPN14 binds to a C-terminal arginine highly conserved in diverse HPV E7. Our previous efforts to understand how PTPN14 degradation contributes to the carcinogenic activity of high-risk HPV E7 used variants of E7 unable to bind to UBR4. Now, by directly manipulating E7 binding to PTPN14 and using a PTPN14 knockout rescue experiment, we demonstrate that the degradation of PTPN14 is required for high-risk HPV18 E7 to extend keratinocyte life span. Our data show that PTPN14 binding by HPV16 E7 and HPV18 E7 represses keratinocyte differentiation. HPV-positive cancers are frequently poorly differentiated, and the HPV life cycle depends upon keratinocyte differentiation. The finding that PTPN14 binding by HPV E7 impairs differentiation has significant implications for HPV-mediated carcinogenesis and the HPV life cycle.

Project description:The beta human papillomaviruses (HPVs) are subdivided into 5 species (beta-1 to beta-5), and they were first identified in the skin. However, the beta-3 species appears to be more highly represented in the mucosal epithelia than in the skin. Functional studies have also highlighted that beta-3 HPV49 shares some functional similarities with mucosal high-risk (HR) HPV16. Here, we describe the characterization of the in vitro transforming properties of the entire beta-3 species, which includes three additional HPV types: HPV75, HPV76, and HPV115. HPV49, HPV75, and HPV76 E6 and E7 (E6/E7), but not HPV115 E6 and E7, efficiently inactivate the p53 and pRb pathways and immortalize or extend the life span of human foreskin keratinocytes (HFKs). As observed for HR HPV16, cell cycle deregulation mediated by beta-3 HPV E6/E7 expression leads to p16INK4a accumulation, whereas no p16INK4a was detected in beta-2 HPV38 E6/E7 HFKs. As shown for HPV49 E6, HPV75 and HPV76 E6s degrade p53 by an E6AP/proteasome-mediated mechanism. Comparative analysis of cellular gene expression patterns of HFKs containing E6 and E7 from HR HPV16, beta-3 HPV types, and beta-2 HPV38 further highlights the functional similarities of HR HPV16 and beta-3 HPV49, HPV75, and HPV76. The expression profiles of these four HPV HFKs show some similarities and diverge substantially from those of beta-3 HPV115 E6/E7 and beta-2 HPV38 E6/E7 HFKs. In summary, our data show that beta-3 HPV types share some mechanisms with HR HPV types and pave the way for additional studies aiming to evaluate their potential role in human pathologies.IMPORTANCE Human papillomaviruses are currently classified in different genera. Mucosal HPVs belonging to the alpha genus have been clearly associated with carcinogenesis of the mucosal epithelium at different sites. Beta HPV types have been classified as cutaneous. Although findings indicate that some beta HPVs from species 1 and 2 play a role, together with UV irradiation, in skin cancer, very little is known about the transforming properties of most of the beta HPVs. This report shows the transforming activity of E6 and E7 from beta-3 HPV types. Moreover, it highlights that beta-3 HPVs share some biological properties more extensively with mucosal high-risk HPV16 than with beta-2 HPV38. This report provides new paradigms for a better understanding of the biology of the different HPV types and their possible association with lesions at mucosal and/or cutaneous epithelia.

Dataset Information

High-Risk Human Papillomavirus E7 Proteins Target PTPN14 for Degradation.

Publications

High-Risk Human Papillomavirus E7 Proteins Target PTPN14 for Degradation.

Similar Datasets

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