Positive and negative regulation of cell proliferation by E2F-1: influence of protein level and human papillomavirus oncoproteins

1994 ◽  
Vol 14 (12) ◽  
pp. 8241-8249
Author(s):  
R M Melillo ◽  
K Helin ◽  
D R Lowy ◽  
J T Schiller
Keyword(s):  
Human Papillomavirus ◽  
Biological Activities ◽  
Wild Type ◽  
Positive Role ◽  
Hpv16 E6 ◽  
Data Support ◽  
Binding Function ◽  
Growth Inhibitory Activity ◽  
E6 And E7

E2F-1 is a member of a family of transcription factors implicated in the activation of genes required for the progression through the S phase of the cell cycle. We have examined the biological activities of E2F-1 with short-term colony-forming assays and long-term immortalization assays. High levels of E2F-1, produced by transfection of the E2F-1 cDNA under the control of a strong promoter, reduced colony formation in normal human foreskin keratinocytes (NHFKs). This inhibition could not be overcome by wild-type human papillomavirus type 16 (HPV16) E6 and E7, two proteins which cooperate to immortalize NHFKs, or by a transdominant p53 mutant. High levels of E2F-1 also inhibited growth of primary and established fibroblasts. The growth-inhibitory activity required the DNA binding function of E2F-1 but not its transactivation or pRB binding activities. A positive role for lower levels of E2F-1 in NHFK immortalization was established by examining the ability of E2F-1 to complement HPV16 E7 mutants that were unable to cooperate with HPV16 E6 to immortalize NHFKs. Although E2F-1 was unable by itself to cooperate with E6, it did, in conjunction with E6, complement a p24GLY mutant of E7 that is defective for immortalization and binding of pRB and pRB-related proteins. By contrast, E2F-1 was unable to complement two other E7 mutants, p2PRO and p31/32ARG/PRO, which are also defective in the immortalization assay, although their proteins display wild-type binding of pRB in vitro. Since the binding of E7 to pRB results in disruption of pRB-E2F interaction and release of transcriptionally active E2F, the data support the hypothesis that binding of pRB by E7 and the consequence increase in E2F, the data support the hypothesis that binding of pRB by E7 and the consequence increase in E3F activity are important but not sufficient for E7-induced keratinocyte immortalization.

scholarly journals Positive and negative regulation of cell proliferation by E2F-1: influence of protein level and human papillomavirus oncoproteins.

1994 ◽  
Vol 14 (12) ◽  
pp. 8241-8249 ◽  
Author(s):  
R M Melillo ◽  
K Helin ◽  
D R Lowy ◽  
J T Schiller
Keyword(s):  
Human Papillomavirus ◽  
Biological Activities ◽  
Wild Type ◽  
Positive Role ◽  
Hpv16 E6 ◽  
Data Support ◽  
Binding Function ◽  
Growth Inhibitory Activity ◽  
E6 And E7

E2F-1 is a member of a family of transcription factors implicated in the activation of genes required for the progression through the S phase of the cell cycle. We have examined the biological activities of E2F-1 with short-term colony-forming assays and long-term immortalization assays. High levels of E2F-1, produced by transfection of the E2F-1 cDNA under the control of a strong promoter, reduced colony formation in normal human foreskin keratinocytes (NHFKs). This inhibition could not be overcome by wild-type human papillomavirus type 16 (HPV16) E6 and E7, two proteins which cooperate to immortalize NHFKs, or by a transdominant p53 mutant. High levels of E2F-1 also inhibited growth of primary and established fibroblasts. The growth-inhibitory activity required the DNA binding function of E2F-1 but not its transactivation or pRB binding activities. A positive role for lower levels of E2F-1 in NHFK immortalization was established by examining the ability of E2F-1 to complement HPV16 E7 mutants that were unable to cooperate with HPV16 E6 to immortalize NHFKs. Although E2F-1 was unable by itself to cooperate with E6, it did, in conjunction with E6, complement a p24GLY mutant of E7 that is defective for immortalization and binding of pRB and pRB-related proteins. By contrast, E2F-1 was unable to complement two other E7 mutants, p2PRO and p31/32ARG/PRO, which are also defective in the immortalization assay, although their proteins display wild-type binding of pRB in vitro. Since the binding of E7 to pRB results in disruption of pRB-E2F interaction and release of transcriptionally active E2F, the data support the hypothesis that binding of pRB by E7 and the consequence increase in E2F, the data support the hypothesis that binding of pRB by E7 and the consequence increase in E3F activity are important but not sufficient for E7-induced keratinocyte immortalization.

scholarly journals Microwaves can reverse the tumour phenotype of human papillomavirus type 16 (HPV16)-positive keratinocytes in 3D cell culture models: a novel therapy for HPV-associated disease?

2020 ◽  
Vol 2 (7A) ◽  
Author(s):  
Ilaria Epifano ◽  
Michaela J. Conley ◽  
Andrew Stevenson ◽  
John Doorbar ◽  
Sheila V. Graham
Keyword(s):  
Cell Proliferation ◽  
Human Papillomavirus ◽  
Tumour Progression ◽  
Microwave Treatment ◽  
Adjacent Area ◽  
Novel Therapy ◽  
Hpv16 E6 ◽  
Cancerous Lesions ◽  
E6 And E7

High-risk human papillomavirus (HPV) is the causative agent of benign, precancerous and cancerous lesions, in both anogenital and oropharyngeal sites. Increased expression of the viral oncoproteins E6 and E7 are responsible for tumour progression. The treatment of these precancerous and cancerous lesions is invasive, painful and with long-term side effects. Localised microwaves have been used successfully in the clinic for the treatment of verrucas, which are caused by low-risk HPV genotypes (>75% success rate versus >33% for cryotherapy). Moreover, local hyperthermia is known to have anti-tumour effects. Ten-second microwave treatment of 3D in vitro-grown cervical tumour tissues (HPV16-positive SiHa cell) resulted in cell death in the treated zone while the tissue integrity was disrupted in the adjacent area. Microwaves induced apoptosis (induction of cleaved caspase 3) and autophagy (induction of LC3) and inhibited cell proliferation (loss of Ki67 and MCM2) in the entire tissue. Furthermore, HPV16 E6 and E7 expression was reduced in cells in the treated and transition zones, with subsequent induction of expression of the apoptosis-regulator, p53 over a 24 hour period following microwave treatment. Thermal stress, identified with the Heat Shock Protein 70 (HSP70) and translational stress identified by G3BP expression, was observed in the transition zone. In conclusion, we demonstrate that the microwave treatment induces cell stress pathways and inhibits HPV oncoprotein expression that causes tumour progression. Induction of apoptosis and reduced cell proliferation suggest a reversal of the cervical tumour phenotype in the 3D tissues.

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 Phylogenetic analysis and predicted functional effect of protein mutations of E6 and E7 HPV16 strains isolated in Indonesia

2015 ◽  
Vol 24 (4) ◽  
pp. 197-205
Author(s):  
Dwi Wulandari ◽  
Lisnawati Rachmadi ◽  
Tjahjani M. Sudiro
Keyword(s):  
Amino Acids ◽  
Phylogenetic Analysis ◽  
Amino Acid ◽  
Asian American ◽  
Protein Function ◽  
Single Amino Acid ◽  
Hpv16 E6 ◽  
E6 And E7 ◽  
Neutral Mutations

Background: E6 and E7 are oncoproteins of HPV16. Natural amino acid variation in HPV16 E6 can alter its carcinogenic potential. The aim of this study was to analyze phylogenetically E6 and E7 genes and proteins of HPV16 from Indonesia and predict the effects of single amino acid substitution on protein function. This analysis could be used to reduce time, effort, and research cost as initial screening in selection of protein or isolates to be tested in vitro or in vivo.Methods: In this study, E6 and E7 gene sequences were obtained from 12 samples of  Indonesian isolates, which  were compared with HPV16R (prototype) and 6 standard isolates in the category of European (E), Asian (As), Asian-American (AA), African-1 (Af-1), African-2 (Af-2), and North American (NA) branch from Genbank. Bioedit v.7.0.0 was used to analyze the composition and substitution of single amino acids. Phylogenetic analysis of E6 and E7 genes and proteins was performed using Clustal X (1.81) and NJPLOT softwares. Effects of single amino acid substitutions on protein function of E6 and E7 were analysed by SNAP.Results: Java variants and isolate ui66* belonged to European branch, while the others belonged to Asian and African branches. Twelve changes of amino acids were found in E6 and one in E7 proteins. SNAP analysis showed two non neutral mutations, i.e. R10I and C63G in E6 proteins. R10I mutations were found in Af-2 genotype (AF472509) and Indonesian isolates (Af2*), while C63G mutation was found only in Af2*.Conclusion: E6 proteins of HPV16 variants were more variable than E7. SNAP analysis showed that only E6 protein of African-2 branch had functional differences compared to HPV16R.

scholarly journals Biological activities of recombinant chicken leptin C4S analog compared with unmodified leptins

2000 ◽  
Vol 279 (1) ◽  
pp. E116-E123 ◽  
Author(s):  
S. Dridi ◽  
N. Raver ◽  
E. E. Gussakovsky ◽  
M. Derouet ◽  
M. Picard ◽  
...  
Keyword(s):  
Biological Activity ◽  
Food Intake ◽  
Leptin Receptor ◽  
Biological Activities ◽  
Wild Type ◽  
Escherichia Coli Cells ◽  
Prokaryotic Expression Vector ◽  
Long Form

The chicken leptin sequence, in contrast to mammalian leptins, contains an unpaired Cys at position 3 of the original cDNA ( AF012727 ). The presence of an extra Cys may confer a different structure and affect the leptin's biological activity. To address this, we studied the effects of wild-type and mutated (C4S) chicken leptins in vitro and in vivo and compared them with mammalian leptin prepared from ovine leptin cDNA. The prokaryotic expression vector pMON, encoding full-size A(−1) chicken leptin ( AF012727 ), was mutated using a mutagenesis kit, yielding the C4S analog. Escherichia coli cells transformed with this vector overexpressed large amounts of chicken leptin C4S upon induction with nalidixic acid. The expressed protein, found in the inclusion bodies, was refolded and purified to homogeneity on a Q-Sepharose column, yielding three electrophoretically pure fractions, eluted from the column by 100, 125, and 150 mM NaCl, respectively. All three fractions showed a single band of the expected molecular mass (16 kDa) and were composed of >95% monomeric protein. Proper refolding was evidenced by comparing the circular dichroism spectrum of the analog with spectra of nonmutated chicken and ovine leptins. The biological activity of the C4S analog was evidenced by its ability to stimulate proliferation of leptin-sensitive BAF/3 cells transfected with a long form of human leptin receptor construct similar to its nonmutated counterpart, indicating that Cys4 plays no role in leptin activity. The in vitro activity of both wild-type and mutated chicken leptins was ∼10-fold lower than that of ovine leptin. After intravenous or intraperitoneal injections, C4S analog and the nonmutated chicken and ovine leptins all lowered the food intake of starved 9-day-old broiler or 5-wk-old layer male chickens by 11–34%. Monitoring food behavior revealed that the attenuated food intake resulted not from a decreased number of approaches to the feeders but from a decrease in the average time spent eating during each approach.

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 Influence of Physiologic Folate Deficiency on Human Papillomavirus Type 16 (HPV16)-harboring Human Keratinocytes in Vitro and in Vivo

2012 ◽  
Vol 287 (15) ◽  
pp. 12559-12577 ◽  
Author(s):  
Suhong Xiao ◽  
Ying-Sheng Tang ◽  
Rehana A. Khan ◽  
Yonghua Zhang ◽  
Praveen Kusumanchi ◽  
...  
Keyword(s):  
Human Keratinocytes ◽  
Folate Deficiency ◽  
Hpv16 E6 ◽  
Immunodeficient Mice ◽  
E6 And E7 ◽  
Nutrition Sensitive ◽  
Hnrnp E1 ◽  
L1 And L2

Although HPV16 transforms infected epithelial tissues to cancer in the presence of several co-factors, there is insufficient molecular evidence that poor nutrition has any such role. Because physiological folate deficiency led to the intracellular homocysteinylation of heterogeneous nuclear ribonucleoprotein E1 (hnRNP-E1) and activated a nutrition-sensitive (homocysteine-responsive) posttranscriptional RNA operon that included interaction with HPV16 L2 mRNA, we investigated the functional consequences of folate deficiency on HPV16 in immortalized HPV16-harboring human (BC-1-Ep/SL) keratinocytes and HPV16-organotypic rafts. Although homocysteinylated hnRNP-E1 interacted with HPV16 L2 mRNA cis-element, it also specifically bound another HPV16 57-nucleotide poly(U)-rich cis-element in the early polyadenylation element (upstream of L2̂L1 genes) with greater affinity. Together, these interactions led to a profound reduction of both L1 and L2 mRNA and proteins without effects on HPV16 E6 and E7 in vitro, and in cultured keratinocyte monolayers and HPV16-low folate-organotypic rafts developed in physiological low folate medium. In addition, HPV16-low folate-organotypic rafts contained fewer HPV16 viral particles, a similar HPV16 DNA viral load, and a much greater extent of integration of HPV16 DNA into genomic DNA when compared with HPV16-high folate-organotypic rafts. Subcutaneous implantation of 18-day old HPV16-low folate-organotypic rafts into folate-replete immunodeficient mice transformed this benign keratinocyte-derived raft tissue into an aggressive HPV16-induced cancer within 12 weeks. Collectively, these studies establish a likely molecular linkage between poor folate nutrition and HPV16 and predict that nutritional folate and/or vitamin-B12 deficiency, which are both common worldwide, will alter the natural history of HPV16 infections and also warrant serious consideration as reversible co-factors in oncogenic transformation of HPV16-infected tissues to cancer.

scholarly journals Bioinformatics Prediction of miRNAs Targeting E6 and E7 Genes in Human Papillomavirus Types 16 and 18 in Cervical Cancer

2020 ◽  
Vol 23 (3) ◽  
pp. 374-385
Author(s):  
Tahere Azimi ◽  
◽  
Malihe Bagheri ◽  
Mahdi Pariyan ◽  
Behzad Khansarinejad ◽  
...  
Keyword(s):  
Cervical Cancer ◽  
Human Papillomavirus ◽  
Early Stage ◽  
Medical Sciences ◽  
Ethical Considerations ◽  
E7 Gene ◽  
Bioinformatics Databases ◽  
E6 And E7 ◽  
New Biomarkers

Background and Aim: Cervical Cancer (CC) is the third most common malignancy in the women, the main cause of which is human papillomavirus (HPV). Both E6 and E7 oncogenes of the virus play an important role in its tumorigenesis. Today, methods available for screening CC are not capable of detecting the disease at an early stage. Therefore, it is important to identify new biomarkers for early detection of this cancer. For this purpose, in the present study, miRNAs targeting the two oncogenes E6 and E7 of human papillomavirus (types 16 and 18) were studied in CC by bioinformatics. Methods & Materials: First, using the NCBI database, the E6 and E7 gene sequences were obtained for both human papillomavirus types 16 and 18. Then, using the miRBase and RNA22 bioinformatics databases, the most appropriate targeting miRNAs for these genes were selected. Ethical Considerations: This study was approved by Ethics Committee of Arak University of Medical Sciences. Results: Based on the P obtained from bioinformatics databases, miRNA including miR-92a-5p (P=7.51e-2), miR-195-3p (P=2.24e-1), miR-34a-5p (P=2.73e-1) and miR-155-5p (P=4.95e-2) were introduced for the two genes E6 and E7. Conclusion: Results from bioinformatics studies revealed that of the four miRNAs identified, miR-155-5p and miR-92a-5p are probably the targeting miRNAs specific for the E6 and E7 genes, respectively. Therefore, it seems that these miRNAs can be a suitable candidate for in vitro studies in CC patients.

scholarly journals Identification of a Novel Specific Cucurbitadienol Synthase Allele in Siraitia grosvenorii Correlates with High Catalytic Efficiency

Molecules ◽  
2019 ◽  
Vol 24 (3) ◽  
pp. 627 ◽  
Author(s):  
Jing Qiao ◽  
Zuliang Luo ◽  
Zhe Gu ◽  
Yanling Zhang ◽  
Xindan Zhang ◽  
...  
Keyword(s):  
Molecular Breeding ◽  
Specific Activity ◽  
Biological Activities ◽  
Enzyme Reaction ◽  
Catalytic Efficiency ◽  
Wild Type ◽  
Siraitia Grosvenorii ◽  
Wide Range ◽  
Triterpenoid Glycosides

Mogrosides, the main bioactive compounds isolated from the fruits of Siraitia grosvenorii, are a group of cucurbitane-type triterpenoid glycosides that exhibit a wide range of notable biological activities and are commercially available worldwide as natural sweeteners. However, the extraction cost is high due to their relatively low contents in plants. Therefore, molecular breeding needs to be achieved when conventional plant breeding can hardly improve the quality so far. In this study, the levels of 21 active mogrosides and two precursors in 15 S. grosvenorii varieties were determined by HPLC-MS/MS and GC-MS, respectively. The results showed that the variations in mogroside V content may be caused by the accumulation of cucurbitadienol. Furthermore, a total of four wild-type cucurbitadienol synthase protein variants (50R573L, 50C573L, 50R573Q, and 50C573Q) based on two missense mutation single nucleotide polymorphism (SNP) sites were discovered. An in vitro enzyme reaction analysis indicated that 50R573L had the highest activity, with a specific activity of 10.24 nmol min−1 mg−1. In addition, a site-directed mutant, namely, 50K573L, showed a 33% enhancement of catalytic efficiency compared to wild-type 50R573L. Our findings identify a novel cucurbitadienol synthase allele correlates with high catalytic efficiency. These results are valuable for the molecular breeding of luohanguo.

scholarly journals The Interaction between Human Papillomavirus Type 16 and FADD Is Mediated by a Novel E6 Binding Domain

2008 ◽  
Vol 82 (19) ◽  
pp. 9600-9614 ◽  
Author(s):  
Sandy S. Tungteakkhun ◽  
Maria Filippova ◽  
Jonathan W. Neidigh ◽  
Nadja Fodor ◽  
Penelope J. Duerksen-Hughes
Keyword(s):  
Cervical Cancer ◽  
Human Papillomavirus ◽  
Tumor Necrosis Factor Receptor ◽  
Binding Domain ◽  
Death Domain ◽  
Infected Cells ◽  
E6 And E7 ◽  
Cancer Tissues

ABSTRACT High-risk strains of human papillomavirus, such as types 16 and 18, have been etiologically linked to cervical cancer. Most cervical cancer tissues are positive for both the E6 and E7 oncoproteins, since it is their cooperation that results in successful transformation and immortalization of infected cells. We have reported that E6 binds to tumor necrosis factor receptor 1 and to Fas-associated death domain (FADD) and, in doing so, prevents E6-expressing cells from responding to apoptotic stimuli. The binding site of E6 to FADD localizes to the first 23 amino acids of FADD and has now been further characterized by the use of deletion and site-directed mutants of FADD in pull-down and functional assays. The results from these experiments revealed that mutations of serine 16, serine 18, and leucine 20 obstruct FADD binding to E6, suggesting that these residues are part of the E6 binding domain on FADD. Because FADD does not contain the two previously identified E6 binding motifs, the LxxφLsh motif, and the PDZ motif, a novel binding domain for E6 has been identified on FADD. Furthermore, peptides that correspond to this region can block E6/FADD binding in vitro and can resensitize E6-expressing cells to apoptotic stimuli in vivo. These results demonstrate the existence of a novel E6 binding domain.

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