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Ye J, Zheng L, He Y, Qi X. Human papillomavirus associated cervical lesion: pathogenesis and therapeutic interventions. MedComm (Beijing) 2023; 4:e368. [PMID: 37719443 PMCID: PMC10501338 DOI: 10.1002/mco2.368] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2023] [Revised: 08/20/2023] [Accepted: 08/22/2023] [Indexed: 09/19/2023] Open
Abstract
Human papillomavirus (HPV) is the most prevalent sexually transmitted virus globally. Persistent high-risk HPV infection can result in cervical precancerous lesions and cervical cancer, with 70% of cervical cancer cases associated with high-risk types HPV16 and 18. HPV infection imposes a significant financial and psychological burden. Therefore, studying methods to eradicate HPV infection and halt the progression of precancerous lesions remains crucial. This review comprehensively explores the mechanisms underlying HPV-related cervical lesions, including the viral life cycle, immune factors, epithelial cell malignant transformation, and host and environmental contributing factors. Additionally, we provide a comprehensive overview of treatment methods for HPV-related cervical precancerous lesions and cervical cancer. Our focus is on immunotherapy, encompassing HPV therapeutic vaccines, immune checkpoint inhibitors, and advanced adoptive T cell therapy. Furthermore, we summarize the commonly employed drugs and other nonsurgical treatments currently utilized in clinical practice for managing HPV infection and associated cervical lesions. Gene editing technology is currently undergoing clinical research and, although not yet employed officially in clinical treatment of cervical lesions, numerous preclinical studies have substantiated its efficacy. Therefore, it holds promise as a precise treatment strategy for HPV-related cervical lesions.
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Affiliation(s)
- Jiatian Ye
- Department of Gynecology and ObstetricsKey Laboratory of Birth Defects and Related Diseases of Women and Children (Sichuan University), Ministry of Education, West China Second Hospital, Sichuan UniversityChengduChina
| | - Lan Zheng
- Department of Pathology and Lab MedicineUniversity of Texas MD Anderson Cancer CenterHoustonTexasUSA
| | - Yuedong He
- Department of Gynecology and ObstetricsKey Laboratory of Birth Defects and Related Diseases of Women and Children (Sichuan University), Ministry of Education, West China Second Hospital, Sichuan UniversityChengduChina
| | - Xiaorong Qi
- Department of Gynecology and ObstetricsKey Laboratory of Birth Defects and Related Diseases of Women and Children (Sichuan University), Ministry of Education, West China Second Hospital, Sichuan UniversityChengduChina
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Lototskaja E, Liblekas L, Piirsoo M, Laaneväli A, Ibragimov R, Piirsoo A. Phosphorylation of E2 Serine Residue 402 Is Required for the Transcription and Replication of the HPV5 Genome. J Virol 2023; 97:e0064323. [PMID: 37272841 PMCID: PMC10308906 DOI: 10.1128/jvi.00643-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2023] [Accepted: 05/13/2023] [Indexed: 06/06/2023] Open
Abstract
Cutaneous human papillomavirus type 5 (HPV5) belongs to the supposedly oncogenic β-HPVs associated with specific types of skin and oral cavity cancers. Three viral proteins, namely, helicase E1 and transcription factors E2 and E8^E2, are master regulators of the viral life cycle. HPV5 E2 is a transcriptional activator that also participates in the E1-dependent replication and nuclear retention of the viral genome, whereas E8^E2 counterbalances the activity of E2 and inhibits HPV transcription and replication. In the present study, we demonstrate that the HPV5 E2 protein is extensively phosphorylated by cellular protein kinases, and serine residue 402 (S402) is the highest scoring phosphoacceptor site. This residue is located within a motif conserved among many β-HPVs and in the oncogenic HPV31 α-type. Using the nonphosphorylatable and phosphomimetic mutants, we demonstrate that phosphorylation of the E2 S402 residue is required for the transcription and replication of the HPV5 genome in U2OS cells and human primary keratinocytes. Mechanistically, the E2-S402-phopshodeficient protein is unable to trigger viral gene transcription and has an impaired ability to support E1-dependent replication, but the respective E8^E2-S213 mutant displays no phenotype. However, phosphorylation of the E2 S402 residue has no impact on the E2 stability, subcellular localization, self-assembly, DNA-binding capacity, and affinity to the E1 and BRD4 proteins. Further studies are needed to identify the protein kinase(s) responsible for this phosphorylation. IMPORTANCE Human papillomavirus type 5 (HPV5) may play a role in the development of specific types of cutaneous and head and neck cancers. The persistence of the HPV genome in host cells depends on the activity of its proteins, namely, a helicase E1 and transcription/replication factor E2. The latter also facilitates the attachment of episomal viral genomes to host cell chromosomes. In the present study, we show that the HPV5 E2 protein is extensively phosphorylated by host cell protein kinases, and we identify serine residue 402 as the highest scoring phosphoacceptor site of E2. We demonstrate that the replication of the HPV5 genome may be blocked by a single point mutation that prevents phosphorylation of this serine residue and switches off the transcriptional activity of the E2 protein. The present study contributes to a better understanding of β-HPV5 replication and its regulation by host cell protein kinases.
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Affiliation(s)
| | - Lisett Liblekas
- Institute of Technology, University of Tartu, Tartu, Estonia
| | - Marko Piirsoo
- Institute of Technology, University of Tartu, Tartu, Estonia
| | | | | | - Alla Piirsoo
- Institute of Technology, University of Tartu, Tartu, Estonia
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Bienkowska-Haba M, Zwolinska K, Keiffer T, Scott RS, Sapp M. Human Papillomavirus Genome Copy Number Is Maintained by S-Phase Amplification, Genome Loss to the Cytosol during Mitosis, and Degradation in G 1 Phase. J Virol 2023; 97:e0187922. [PMID: 36749071 PMCID: PMC9972943 DOI: 10.1128/jvi.01879-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2022] [Accepted: 01/17/2023] [Indexed: 02/08/2023] Open
Abstract
The current model of human papillomavirus (HPV) replication is comprised of three modes of replication. Following infectious delivery, the viral genome is amplified during the establishment phase to reach up to some hundred copies per cell. The HPV genome copy number remains constant during the maintenance stage. The differentiation of infected cells induces HPV genome amplification. Using highly sensitive in situ hybridization (DNAscope) and freshly HPV16-infected as well as established HPV16-positive cell lines, we observed that the viral genome is amplified in each S phase of undifferentiated keratinocytes cultured as monolayers. The nuclear viral genome copy number is reset to pre-S-phase levels during mitosis. The majority of the viral genome fails to tether to host chromosomes and is lost to the cytosol. Cytosolic viral genomes gradually decrease during cell cycle progression. The loss of cytosolic genomes is blocked in the presence of NH4Cl or other drugs that interfere with lysosomal acidification, suggesting the involvement of autophagy in viral genome degradation. These observations were also made with HPV31 cell lines obtained from patient samples. Cytosolic viral genomes were not detected in UMSCC47 cells carrying integrated HPV16 DNA. Analyses of organotypic raft cultures derived from keratinocytes harboring episomal HPV16 revealed the presence of cytosolic viral genomes as well. We conclude that HPV maintains viral genome copy numbers by balancing viral genome amplification during S phase with the loss of viral genomes to the cytosol during mitosis. It seems plausible that restrictions to viral genome tethering to mitotic chromosomes reset genome copy numbers in each cell cycle. IMPORTANCE HPV genome maintenance is currently thought to be achieved by regulating the expression and activity of the viral replication factors E1 and E2. In addition, the E8^E2 repressor has been shown to be important for restricting genome copy numbers by competing with E1 and E2 for binding to the viral origin of replication and by recruiting repressor complexes. Here, we demonstrate that the HPV genome is amplified in each S phase. The nuclear genome copy number is reset during mitosis by a failure of the majority of the genomes to tether to mitotic chromosomes. Rather, HPV genomes accumulate in the cytoplasm of freshly divided cells. Cytosolic viral DNA is degraded in G1 in a lysosome-dependent manner, contributing to the genome copy reset. Our data imply that the mode of replication during establishment and maintenance is the same and further suggest that restrictions to genome tethering significantly contribute to viral genome maintenance.
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Affiliation(s)
- Malgorzata Bienkowska-Haba
- Department of Microbiology and Immunology, Feist Weiller Cancer Center, Louisiana State University Health Sciences Center, Shreveport, Louisiana, USA
| | - Katarzyna Zwolinska
- Department of Microbiology and Immunology, Feist Weiller Cancer Center, Louisiana State University Health Sciences Center, Shreveport, Louisiana, USA
| | - Timothy Keiffer
- Department of Microbiology and Immunology, Feist Weiller Cancer Center, Louisiana State University Health Sciences Center, Shreveport, Louisiana, USA
| | - Rona S. Scott
- Department of Microbiology and Immunology, Feist Weiller Cancer Center, Louisiana State University Health Sciences Center, Shreveport, Louisiana, USA
| | - Martin Sapp
- Department of Microbiology and Immunology, Feist Weiller Cancer Center, Louisiana State University Health Sciences Center, Shreveport, Louisiana, USA
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Kanginakudru S, Gilson T, Jose L, Androphy EJ. Effects of Caffeine, a DNA Damage Response Inhibitor, on Papillomavirus Genome Replication. Pathogens 2022; 11:1298. [PMID: 36365049 PMCID: PMC9698569 DOI: 10.3390/pathogens11111298] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2022] [Revised: 10/02/2022] [Accepted: 11/02/2022] [Indexed: 09/04/2023] Open
Abstract
Epidemiological studies have revealed that caffeinated coffee imparts a reduced risk of oropharyngeal cancer, of which human papillomavirus (HPV) is one of the causative agents. Caffeine is a known inhibitor of the DNA damage response (DDR) pathway. We sought to test the effects of caffeine on the early replication of the HPV31 virus. It has been reported that the inhibition of several factors necessary for the DDR during the differentiation-dependent stage of HPV block genome amplification, while the HPV genome maintenance replication was unaffected. We first studied the effects of caffeine in the earliest stages of viral infection. Using pseudo-virions (PsV) expressing an m-Cherry reporter gene and quasi-virions (QsV) containing HPV31 genomes to mediate the infection, we found no evidence that caffeine impeded the viral entry; however, the infected cells displayed a reduced HPV copy number. In contrast, caffeine exposure increased the copy number of HPV31 episomes in the transient transfection assays and in the CIN612E cells that stably maintain viral episomes. There was a concomitant increase in the steady state levels of the HPV31 E1 and E2 transcripts, along with increased E2 loading at the viral origin of replication (ori). These results suggest that the caffeine-mediated inhibition of the DDR reduces viral genome replication in the early stage of infection, in contrast to the maintenance stage, in which the inhibition of the DDR may lead to an increase in viral amplicon replication.
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Affiliation(s)
- Sriramana Kanginakudru
- Department of Dermatology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Timra Gilson
- Department of Dermatology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Leny Jose
- Department of Dermatology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Elliot J. Androphy
- Department of Dermatology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
- Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
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5
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SETD6 Regulates E2-Dependent Human Papillomavirus Transcription. J Virol 2022; 96:e0129522. [PMID: 36300937 PMCID: PMC9682981 DOI: 10.1128/jvi.01295-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Human papillomaviruses (HPV) cause cervical, anogenital, and oral cancers. Brd4 plays an important role in the HPV life cycle. SETD6 was recently shown to methylate Brd4. The current study demonstrates that methylation of Brd4 by SETD6 in HPV-episomal cells is required for the activation of viral transcription. This study illustrates a novel regulatory mechanism involving E2, Brd4, and SETD6 in the HPV life cycle and provides insight into the multiple roles of Brd4 in viral pathogenesis.
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Chen IP, Ott M. Viral Hijacking of BET Proteins. Viruses 2022; 14:v14102274. [PMID: 36298829 PMCID: PMC9609653 DOI: 10.3390/v14102274] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2022] [Revised: 10/09/2022] [Accepted: 10/11/2022] [Indexed: 11/29/2022] Open
Abstract
Proteins of the bromodomain and exterminal domain (BET) family mediate critical host functions such as cell proliferation, transcriptional regulation, and the innate immune response, which makes them preferred targets for viruses. These multidomain proteins are best known as transcriptional effectors able to read acetylated histone and non-histone proteins through their tandem bromodomains. They also contain other short motif-binding domains such as the extraterminal domain, which recognizes transcriptional regulatory proteins. Here, we describe how different viruses have evolved to hijack or disrupt host BET protein function through direct interactions with BET family members to support their own propagation. The network of virus-BET interactions emerges as highly intricate, which may complicate the use of small-molecule BET inhibitors-currently in clinical development for the treatment of cancer and cardiovascular diseases-to treat viral infections.
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Affiliation(s)
- Irene P. Chen
- Gladstone Institutes, San Francisco, CA 94158, USA
- Department of Medicine, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Melanie Ott
- Gladstone Institutes, San Francisco, CA 94158, USA
- Department of Medicine, University of California, San Francisco, San Francisco, CA 94143, USA
- Chan Zuckerberg Biohub, San Francisco, CA 94158, USA
- Correspondence:
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Exome sequencing reveals candidate mutations implicated in sinonasal carcinoma and malignant transformation of sinonasal inverted papilloma. Oral Oncol 2021; 124:105663. [PMID: 34915258 DOI: 10.1016/j.oraloncology.2021.105663] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2021] [Revised: 11/19/2021] [Accepted: 12/01/2021] [Indexed: 11/20/2022]
Abstract
We explored somatic mutations in dysplastic sinonasal inverted papilloma (SNIP), SNIP with concomitant sinonasal squamous cell carcinoma (SNSCC), and SNSCC without preceding SNIP. Ten SNIP and SNSCC samples were analyzed with exome sequencing and tested for human papillomavirus. The identified mutations were compared to the most frequently mutated genes in head and neck squamous cell carcinoma (HNSCC) in the COSMIC database. Exome sequencing data were also analyzed for mutations not previously linked to SNSCC. Seven of the most commonly mutated genes in HNSCC and SNSCC in COSMIC harbored mutations in our data. In addition, we identified mutations in 23 genes that are likely to contribute to SNIP and SNSCC oncogenesis.
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Jose L, Gilson T, Androphy EJ, DeSmet M. Regulation of the Human Papillomavirus Lifecyle through Post-Translational Modifications of the Viral E2 Protein. Pathogens 2021; 10:793. [PMID: 34201556 PMCID: PMC8308518 DOI: 10.3390/pathogens10070793] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2021] [Revised: 06/13/2021] [Accepted: 06/18/2021] [Indexed: 01/28/2023] Open
Abstract
The human papillomavirus (HPV) is a DNA tumor virus that infects cutaneous and mucosal epithelia where high-risk (HR) HPV infections lead to cervical, oropharyngeal, and anogenital cancers. Worldwide, nearly 5% of all cancers are caused by HR HPV. The viral E2 protein is essential for episomal replication throughout the viral lifecycle. The E2 protein is regulated by phosphorylation, acetylation, sumoylation, and ubiquitination. In this mini-review, we summarize the recent advancements made to identify post translational modifications within E2 and their ability to control viral replication.
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Affiliation(s)
- Leny Jose
- Department of Dermatology, Indiana University School of Medicine, Indianapolis, IN 46202, USA; (L.J.); (T.G.); (E.J.A.)
| | - Timra Gilson
- Department of Dermatology, Indiana University School of Medicine, Indianapolis, IN 46202, USA; (L.J.); (T.G.); (E.J.A.)
| | - Elliot J. Androphy
- Department of Dermatology, Indiana University School of Medicine, Indianapolis, IN 46202, USA; (L.J.); (T.G.); (E.J.A.)
- Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Marsha DeSmet
- Department of Dermatology, Indiana University School of Medicine, Indianapolis, IN 46202, USA; (L.J.); (T.G.); (E.J.A.)
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BRD4S interacts with viral E2 protein to limit human papillomavirus late transcription. J Virol 2021; 95:JVI.02032-20. [PMID: 33731454 PMCID: PMC8139696 DOI: 10.1128/jvi.02032-20] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
The E2 protein encoded by human papillomaviruses (HPV) is a sequence-specific DNA-binding protein that recruits viral and cellular proteins. Bromodomain-containing protein 4 (BRD4) is a highly conserved interactor for E2 proteins that has been linked to E2's functions as transcription modulator, activator of viral replication and segregation factor for viral genomes. In addition to BRD4, a short form of BRD4 (BRD4S) is expressed from the BRD4 gene which lacks the C-terminal domain of BRD4. E2 proteins interact with the C-terminal motif (CTM) of BRD4, but a recent study suggested that the phospho-dependent interaction domain (PDID) and the basic interaction domain (BID) in BRD4 also bind to E2. These domains are also present in BRD4S. We now find that HPV31 E2 interacts with the isolated PDID domain in living cells and also with BRD4S which is present in detectable amounts in HPV-positive cell lines and is recruited into HPV31 E1 and E2 induced replication foci. Overexpression and knockdown experiments surprisingly indicate that BRD4S inhibits activities of E2. In line with that, the specific knockdown of BRD4S in the HPV31-positive CIN612-9E cell line induces mainly late viral transcripts. This occurs only in undifferentiated but not differentiated cells in which the productive viral replication cycle is induced. These data suggest that the BRD4S-E2 interaction is important to prevent HPV late gene expression in undifferentiated keratinocytes which may contribute to immune evasion and HPV persistence.ImportanceHuman papillomaviruses (HPV) have coevolved with their host by using cellular factors like bromodomain-containing protein 4 (BRD4) to control viral processes such as genome maintenance, gene expression and replication. We here show that, in addition to the C-terminal motif in BRD4, the phospho-dependent interaction domain in BRD4 interacts with E2 proteins which enable the recruitment of BRD4S, the short isoform of BRD4, to E2. Knock-down and overexpression of BRD4S reveals that BRD4S is a negative regulator of E2 activities. Importantly, the knockdown of BRD4S induces mainly L1 transcripts in undifferentiated CIN612-9E cells, which maintain replicating HPV31 genomes. Our study reveals an inhibitory role of BRD4S on HPV transcription, which may serve as an immune escape mechanism by the suppression of L1 transcripts and thus contribute to the establishment of persistent HPV infections.
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Pyk2 Regulates Human Papillomavirus Replication by Tyrosine Phosphorylation of the E2 Protein. J Virol 2020; 94:JVI.01110-20. [PMID: 32727877 DOI: 10.1128/jvi.01110-20] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2020] [Accepted: 07/24/2020] [Indexed: 12/29/2022] Open
Abstract
The human papillomavirus (HPV) E2 protein is a key regulator of viral transcription and replication. In this study, we demonstrate that the nonreceptor tyrosine kinase Pyk2 phosphorylates tyrosine 131 in the E2 transactivation domain. Both depletion of Pyk2 and treatment with a Pyk2 kinase inhibitor increased viral DNA content in keratinocytes that maintain viral episomes. The tyrosine-to-glutamic acid (E) mutant Y131E, which may mimic phosphotyrosine, failed to stimulate transient DNA replication, and genomes with this mutation were unable to establish stable episomes in keratinocytes. Using coimmunoprecipitation assays, we demonstrate that the Y131E is defective for binding to the C-terminal motif (CTM) of Bromodomain-containing protein 4 (Brd4). These data imply that HPV replication depends on E2 Y131 interaction with the pTEFb binding domain of Brd4.IMPORTANCE Human papillomaviruses are the major causative agents of cervical, oral, and anal cancers. The present study demonstrates that the Pyk2 tyrosine kinase phosphorylates E2 at tyrosine 131, interfering with genome replication. We provide evidence that phosphorylation of E2 prevents binding to the Brd4-CTM. Our findings add to the understanding of molecular pathways utilized by the virus during its vegetative life cycle and offers insights into the host-virus interactome.
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The SMC5/6 Complex Represses the Replicative Program of High-Risk Human Papillomavirus Type 31. Pathogens 2020; 9:pathogens9100786. [PMID: 32992873 PMCID: PMC7599729 DOI: 10.3390/pathogens9100786] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2020] [Revised: 09/18/2020] [Accepted: 09/23/2020] [Indexed: 01/04/2023] Open
Abstract
The multi-subunit structural maintenance of chromosomes (SMC) 5/6 complex includes SMC6 and non-SMC element (NSE)3. SMC5/6 is essential for homologous recombination DNA repair and functions as an antiviral factor during hepatitis B (HBV) and herpes simplex-1 (HSV-1) viral infections. Intriguingly, SMC5/6 has been found to associate with high-risk human papillomavirus (HPV) E2 regulatory proteins, but the functions of this interaction and its role during HPV infection remain unclear. Here, we further characterize SMC5/6 interactions with HPV-31 E2 and its role in the HPV life cycle. Co-immunoprecipitation (co-IP) revealed that SMC6 interactions with HPV-31 E2 require the E2 transactivation domain, implying that SMC5/6 interacts with full-length E2. Using chromatin immunoprecipitation, we found that SMC6 is present on HPV-31 episomes at E2 binding sites. The depletion of SMC6 and NSE3 increased viral replication and transcription in keratinocytes maintaining episomal HPV-31, indicating that SMC5/6 restricts the viral replicative program. SMC6 interactions with E2 were reduced in the presence of HPV-31 E1, suggesting that SMC6 and E1 compete for E2 binding. Our findings demonstrate SMC5/6 functions as a repressor of the viral replicative program and this may involve inhibiting the initiation of viral replication.
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Gilson T, Culleton S, Xie F, DeSmet M, Androphy EJ. Human Papillomavirus 31 Tyrosine 102 Regulates Interaction with E2 Binding Partners and Episomal Maintenance. J Virol 2020; 94:e00590-20. [PMID: 32493825 PMCID: PMC7394896 DOI: 10.1128/jvi.00590-20] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2020] [Accepted: 05/17/2020] [Indexed: 12/16/2022] Open
Abstract
Several serine and threonine residues of the papillomavirus early E2 protein have been found to be phosphorylated. In contrast, only one E2 tyrosine phosphorylation site in BPV-1 (tyrosine 102) and one in HPV-16/31 (tyrosine 138) site have been characterized. Between BPV-1 and HPV-31 E2, 8 of the 11 tyrosines are conserved in the N-terminal domain, suggesting that phosphorylation of tyrosines has an essential role in E2 biology. In this study, we examine the effect of Y102 phosphorylation on HPV-31 E2 biology. Y102 proteins mutated either to the potential phospho-mimetic glutamic acid (Y102E) or to the nonphosphorylated homologue phenylalanine (Y102F) remain nuclear; however, Y102E is more associated with the nuclear matrix fraction. This is consistent with the inability of Y102E to bind TopBP1. Both BPV-1 and HPV-31 Y102E are similar in that neither binds the C terminus of Brd4, but in all other aspects the mutant behaves differently between the two families of papillomaviruses. BPV-1 Y102E was unable to bind E1 and did not replicate in a transient in vitro assay, while HPV-31 Y102E binds E1 and was able to replicate, albeit at lower levels than wild type. To examine the effect of E2 mutations under more native-like infection conditions, a neomycin-selectable marker was inserted into L1/L2 of the HPV-31 genome, creating HPV-31neo. This genome was maintained in every cell line tested for at least 50 days posttransfection/infection. Y102E in both transfection and infection conditions was unable to maintain high episome copy numbers in epithelial cell lines.IMPORTANCE Posttranslational modifications by phosphorylation can change protein activities, binding partners, or localization. Tyrosine 102 is conserved between delta papillomavirus BPV-1 and alpha papillomavirus HPV-31 E2. We characterized mutations of HPV-31 E2 for interactions with relevant cellular binding partners and replication in the context of the viral genome.
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Affiliation(s)
- Timra Gilson
- Department of Dermatology, Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Sara Culleton
- Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Fang Xie
- Department of Dermatology, Chinese People's Liberation Army General Hospital, Beijing, China
| | - Marsha DeSmet
- Department of Dermatology, Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Elliot J Androphy
- Department of Dermatology, Indiana University School of Medicine, Indianapolis, Indiana, USA
- Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, Indiana, USA
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Phosphorylation of the Human Papillomavirus E2 Protein at Tyrosine 138 Regulates Episomal Replication. J Virol 2020; 94:JVI.00488-20. [PMID: 32350070 DOI: 10.1128/jvi.00488-20] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2020] [Accepted: 04/19/2020] [Indexed: 01/15/2023] Open
Abstract
The papillomavirus (PV) E2 protein is a critical regulator of viral transcription and genome replication. We previously reported that tyrosine (Y) 138 of HPV-31 E2 is phosphorylated by the fibroblast growth factor receptor 3 (FGFR3) kinase. In this study, we generated quasiviruses containing G418-selectable HPV-31 genomes with phosphodeficient phenylalanine mutant E2 Y138F and phosphomimetic glutamic acid mutant Y138E. We observed significantly fewer early viral transcripts immediately after infection with these Y138 mutant genomes even though E2 occupancy at the viral origin was equivalent to that of wild-type E2. Keratinocytes infected with Y138F quasiviruses formed stable colonies, and the genomes were maintained as episomes, while those infected with Y138E quasiviruses did not. We previously reported that the HPV-31 E2 Y138 mutation to glutamic acid did not bind to the Brd4 C-terminal motif (CTM). Here, we demonstrate that HPV-16 E2 Y138E bound to full-length Brd4 but not to the Brd4 CTM. We conclude that association of E2 with the Brd4 CTM is necessary for viral genome replication and suggest that this interaction can be regulated by phosphorylation of E2 Y138.IMPORTANCE Papillomavirus (PV) is a double-stranded DNA tumor virus infecting the cutaneous and mucosal epithelium. The PV E2 protein associates with a number of cellular factors to mediate replication of the HPV genome. Fibroblast growth factor receptor 3 (FGFR3) regulates HPV replication through phosphorylation of tyrosine 138 in the HPV E2 protein. Employing a quasivirus infection model and selection for G418 resistant genomes, we demonstrated that Y138 is a critical residue for Brd4 association and that inability to complex with Brd4 does not support episomal replication.
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