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Ndisang D, Lorenzato F, Sindos M, Khan A, Singer A, Latchman DS. The HPV Cellular Transactivator Brn-3a Can Be Used to Predict Cervical Adenocarcinoma and Squamous Carcinoma Precancer Lesions in the Developed and Developing Worlds. Obstet Gynecol Int 2010; 2009:359457. [PMID: 20224757 PMCID: PMC2836136 DOI: 10.1155/2009/359457] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2009] [Revised: 12/27/2009] [Accepted: 12/29/2009] [Indexed: 11/18/2022] Open
Abstract
The cellular transactivator Brn-3a has previously been shown to be expressed at elevated levels in the cervix of women with squamous cell carcinoma of the cervix (SCC) and to activate the expression of HPV E6 mRNA. In this study, we show that common and rare cervical precancer lesions, including those of adenocarcinoma (AC), which are usually difficult to diagnose using classical procedures, also expressed high levels of Brn-3a and can be diagnosed by measuring the levels of Brn-3a and E6 mRNAs.
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Affiliation(s)
- Daniel Ndisang
- Medical Molecular Biology Unit, Institute of Child Health, University College London, 30 Guilford Street, London WC1N 1EH, UK
| | - Felipe Lorenzato
- Instituto Materno Infantil de Pernambuco (IMIP), Rua dos coelhos, 300 Boa Vista Recife 1393, Pernambuco, Brazil
| | - Michael Sindos
- Medical Molecular Biology Unit, Institute of Child Health, University College London, 30 Guilford Street, London WC1N 1EH, UK
| | - Ashfaq Khan
- Medical Molecular Biology Unit, Institute of Child Health, University College London, 30 Guilford Street, London WC1N 1EH, UK
- Department of Women's and Children's Health, The Whittington Hospital, Highgate Hill, London N19 5NF, UK
| | - Albert Singer
- Department of Women's and Children's Health, The Whittington Hospital, Highgate Hill, London N19 5NF, UK
| | - David S. Latchman
- Medical Molecular Biology Unit, Institute of Child Health, University College London, 30 Guilford Street, London WC1N 1EH, UK
- Birkbeck, University of London, Malet Street, London WC1E 7HX, UK
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Khan AM, Singer A. Biomarkers in cervical precancer management: the new frontiers. Future Oncol 2008; 4:515-24. [DOI: 10.2217/14796694.4.4.515] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The major cause of cervical cancer and its pre-invasive lesions is persistent infections with oncogenic human papillomavirus (HPV). Viral replication and integration in the cervix depends on the ordered expression of viral gene products, which can lead to overexpression of multiple molecular proteins or biomarkers. These novel biomarkers allow the monitoring of essential molecular events in histological or cytological specimens and are likely to improve the detection of lesions that have a high risk of progression in both primary screening and triage settings. This review focuses on these molecular markers and their role in the diagnosis and management of cervical dysplasia and cancer.
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Affiliation(s)
- Ashfaq M Khan
- Whittington Hospital NHS, Women’s Health, London N19 5NF, UK and, Institute of Child Health, University College London, London, UK
| | - Albert Singer
- Whittington Hospital NHS, Gynaecological Research, Women’s Health, London N19 5NF, UK
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Ndisang D, Lorenzato F, Sindos M, Singer A, Latchman DS. Detection of cervical abnormalities in a developing country using measurement of Brn-3a in cervical smears. Gynecol Oncol 2006; 100:89-94. [PMID: 16126264 DOI: 10.1016/j.ygyno.2005.07.109] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2005] [Revised: 07/24/2005] [Accepted: 07/26/2005] [Indexed: 11/30/2022]
Abstract
OBJECTIVE We have previously shown that Brn-3a is elevated in biopsies from women in the United Kingdom with high grade cervical neoplasia, and that it specifically trans-activates the HPV URR in vitro and in vivo. The aim of this study is to establish the relationship of Brn-3a, HPV E6 and pathological diagnosis in cervical smear from women in a developing country with a high prevalence of cervical disease. This is a follow-up of our previous work in which for the first time Brn-3a and E6 levels in cervical smears from women in United Kingdom were shown to correlate with the histological diagnosis of cervical neoplasia and were even better in predicting underlying pre-malignant disease than conventional procedures. METHOD Cervical smears from 295 women with cervical abnormalities attending gynecological clinics in Brazil were used to make RNA. The mRNA levels of Brn-3a and HPV E6 were measured and the data obtained were used to establish the relationship between Brn-3a and the histological diagnosis. RESULTS The cellular transcription factor Brn-3a was readily measured in cervical smears from the Brazilian population. Its presence was shown to be frequently associated with the expression of HPV E6. The measured level of Brn-3a parallels the severity of the cervical ailment and predicts the pathological categories. CONCLUSIONS The ability of Brn-3a to predict for cervical ailments is independent to the geographical characteristics of the population, and hence it could be used routinely as an adjunct to colposcopy and pathological diagnosis in developing and developed countries.
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Affiliation(s)
- Daniel Ndisang
- Medical Molecular Biology Unit, Institute of Child Health, University College London, 30 Guilford Street, London WC1N 1EH, UK.
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Ndisang D, Faulkes DJ, Gascoyne D, Lee SA, Ripley BJ, Sindos M, Singer A, Budhram-Mahadeo V, Cason J, Latchman DS. Differential regulation of different human papilloma virus variants by the POU family transcription factor Brn-3a. Oncogene 2005; 25:51-60. [PMID: 16247485 DOI: 10.1038/sj.onc.1209006] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The Brn-3a POU family transcription factor is overexpressed in human cervical carcinoma biopsies and is able to activate expression of the human papilloma virus type 16 (HPV-16) upstream regulatory region (URR), which drives the expression of the E6 and E7 oncoproteins. Inhibition of Brn-3a expression in human cervical cancer cells inhibits HPV gene expression and reduces cellular growth and anchorage independence in vitro as well as the ability to form tumours in vivo. Here, we show that Brn-3a differentially regulates different HPV-16 variants that have previously been shown to be associated with different risks of progression to cervical carcinoma. In human cervical material, Brn-3a levels correlate directly with HPV E6 levels in individuals infected with a high risk variant of HPV-16, whereas this is not the case for a low-risk variant. Moreover, the URRs of high- and intermediate-risk variants are activated by Brn-3a in transfection assays, whereas the URR of a low-risk variant is not. The change of one or two bases in a low-risk variant URR to their equivalent in a higher-risk URR can render the URR responsive to Brn-3a and vice versa. These results help explain why the specific interplay between viral and cellular factors necessary for the progression to cervical carcinoma only occurs in a minority of those infected with HPV-16.
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Affiliation(s)
- D Ndisang
- Medical Molecular Biology Unit, Institute of Child Health, University College London, and Department of Women's and Children's Health, The Whittington Hospital, London, UK
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Sindos M, Ndisang D, Pisal N, Chow C, Singer A, Latchman DS. Measurement of Brn-3a levels in Pap smears provides a novel diagnostic marker for the detection of cervical neoplasia. Gynecol Oncol 2003; 90:366-71. [PMID: 12893201 DOI: 10.1016/s0090-8258(03)00261-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
OBJECTIVES We have previously demonstrated that Brn-3a cellular transcription factor activates transcription of the human papillomavirus (HPV) E6 and E7 oncogenes in human cervical cancer cells and that Brn-3a levels are dramatically elevated in biopsies from women with high-grade cervical neoplasia. The aim of this study was to establish the relationship between Brn-3a levels in Pap smears and the histological diagnoses. We also analysed whether Brn-3a levels can be used in combination with Pap smear to predict the presence of cervical intraepithelial lesion. METHODS Two hundred thirty-eight women who were referred with abnormal Pap smear underwent a diagnostic colposcopy, repeat in-study Pap smear, colposcopically directed biopsy, and assessment of Brn-3a and HPV-16 E6 m-RNA levels. Data were analysed to assess the association between Brn-3a levels and the histological diagnosis. RESULTS Brn-3a was readily measured in smears and showed a statistically significant correlation with the grade of cervical abnormality. Positive Brn-3a is associated with increased relative risk of higher-grade lesion. Moreover, measurement of Brn-3a levels in smears can be used to detect a significant proportion of cervical lesions that were missed by Pap smear. CONCLUSION Measurement of Brn-3a levels in routinely taken Pap smears is a feasible technique that correlates with the severity of the epithelial abnormality and is a useful adjunct to cytology. Brn-3a appears to have great promise since it detects activation of oncogenic HPVs rather than simply detecting their presence, as is currently being done.
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Affiliation(s)
- Michael Sindos
- Institute of Child Health, University College London, 30 Guilford Street, London WC1N 1EH, UK.
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Boulanger A, Liu S, Henningsgaard AA, Yu S, Redmond TM. The upstream region of the Rpe65 gene confers retinal pigment epithelium-specific expression in vivo and in vitro and contains critical octamer and E-box binding sites. J Biol Chem 2000; 275:31274-82. [PMID: 10896939 DOI: 10.1074/jbc.m003441200] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
RPE65 is essential for all-trans- to 11-cis-retinoid isomerization, the hallmark reaction of the retinal pigment epithelium (RPE). Here, we identify regulatory elements in the Rpe65 gene and demonstrate their functional relevance to Rpe65 gene expression. We show that the 5' flanking region of the mouse Rpe65 gene, like the human gene, lacks a canonical TATA box and consensus GC and CAAT boxes. The mouse and human genes do share several cis-acting elements, including an octamer, a nuclear factor one (NFI) site, and two E-box sites, suggesting a conserved mode of regulation. A mouse Rpe65 promoter/beta-galactosidase transgene containing bases -655 to +52 (TR4) of the mouse 5' flanking region was sufficient to direct high RPE-specific expression in transgenic mice, whereas shorter fragments (-297 to +52 or -188 to +52) generated only background activity. Furthermore, transient transfection of analogous TR4/luciferase constructs also directed high reporter activity in the human RPE cell line D407 but weak activity in the non-RPE cell lines HeLa, HepG2, and HS27. Functional binding of potential transcription factors to the octamer sequence, AP-4, and NFI sites was demonstrated by directed mutagenesis, electrophoretic mobility shift assay, and cross-linking. Mutations of these sites abolished binding and corresponding transcriptional activity and indicated that octamer and E-box transcription factors synergistically regulate the RPE65 promoter function. Thus, we have identified the regulatory region in the Rpe65 gene that accounts for tissue-specific expression in the RPE and found that octamer and E-box transcription factors play a critical role in the transcriptional regulation of the Rpe65 gene.
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Affiliation(s)
- A Boulanger
- Laboratory of Retinal Cell and Molecular Biology, NEI, National Institutes of Health, Bethesda, Maryland 20892, USA
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7
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Ndisang D, Budhram-Mahadeo V, Latchman DS. The Brn-3a Transcription Factor Plays a Critical Role in Regulating Human Papilloma Virus Gene Expression and Determining the Growth Characteristics of Cervical Cancer Cells. J Biol Chem 1999; 274:28521-7. [PMID: 10497216 DOI: 10.1074/jbc.274.40.28521] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The Brn-3a POU family transcription factor has previously been shown to activate the human papilloma virus type 16 (HPV-16) promoter driving the expression of the E6- and E7-transforming proteins. Moreover, Brn-3a is overexpressed approximately 300-fold in cervical biopsies from women with cervical intra-epithelial neoplasia type 3 (CIN3) compared with normal cervical material. To test the role of Brn-3a in cervical neoplasia we have manipulated its expression in cervical carcinoma-derived cell lines with or without endogenous HPV genes. In HPV-expressing cells, reduction in Brn-3a expression specifically reduces HPV gene expression, growth rate, saturation density and anchorage-independent growth, whereas these effects are not observed when Brn-3a expression is reduced in cervical cells lacking HPV genomes. Together with our previous observations, these findings indicate a critical role for Brn-3a in regulating HPV gene expression and thereby in controlling the growth/transformation of cervical cells.
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Affiliation(s)
- D Ndisang
- Department of Molecular Pathology, Windeyer Institute of Medical Sciences, University College London, London W1P 6DB, United Kingdom
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8
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Abstract
In the same way as other viral functions, the transcription of viral genes is frequently controlled by cellular regulatory proteins either acting alone or together with virally encoded factors. In this review, I discuss three examples of such regulation in different types of DNA viruses by different members of the POU family of transcription factors, all of which involve viruses which play a role in the aetiology of specific human diseases. These are the glial cell-specific transcription of JC virus which is controlled by the glial cell specific POU factor Tst-1; the regulation of human papillomavirus gene expression in the cervix by positively and negatively acting POU factors and the manner in which the balance between lytic or latent infection with HSV is controlled by positively and negatively acting POU factors which differ in their ability to interact with the virally encoded transactivator VP16. As well as being of interest in themselves, these processes may offer a therapeutic target for controlling the diseases caused by these very different viruses.
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Affiliation(s)
- D S Latchman
- Department of Molecular Pathology, Windeyer Institute of Medical Sciences, University College London Medical School, UK
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9
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Ndisdang D, Morris PJ, Chapman C, Ho L, Singer A, Latchman DS. The HPV-activating cellular transcription factor Brn-3a is overexpressed in CIN3 cervical lesions. J Clin Invest 1998; 101:1687-92. [PMID: 9541499 PMCID: PMC508750 DOI: 10.1172/jci1089] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
The cervical cellular transcription factors Brn-3a and Brn-3b have antagonistic effects on transcription of the human papilloma virus types 16 and 18 E6 and E7 oncogenes, with Brn-3a activating expression and Brn-3b repressing it. We therefore measured expression of Brn-3a and Brn-3b mRNAs in biopsies from 16 women with no detectable cervical abnormality, and in 14 women with cervical intraepithelial neoplasia grade 3 (CIN3) lesions. Although the mean level of Brn-3b expression was similar in both groups, the mean level of Brn-3a expression was over 300-fold higher in the CIN3 samples when compared with normals. Elevated expression of Brn-3a was also detected in 16 histologically normal regions of the cervix adjacent to the CIN3 lesions, indicating that elevation of Brn-3a levels is not confined to the lesion in women with CIN3, and is thus not a consequence of the oncogenic process. The elevated levels of Brn-3a in the CIN3 patient samples, together with the activating effect of Brn-3a on HPV-16 and -18 oncogene expression, suggest that induction of this factor is involved in activating HPV-16 and -18 oncogene expression in the cervix, and hence in the production of cervical cancers induced by HPV.
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Affiliation(s)
- D Ndisdang
- Windeyer Institute of Medical Sciences, University College London Medical School, The Windeyer Building, Cleveland Street, London W1P 6DB, United Kingdom
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Zhao W, Chow LT, Broker TR. Transcription activities of human papillomavirus type 11 E6 promoter-proximal elements in raft and submerged cultures of foreskin keratinocytes. J Virol 1997; 71:8832-40. [PMID: 9343243 PMCID: PMC192349 DOI: 10.1128/jvi.71.11.8832-8840.1997] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Human papillomaviruses (HPVs) replicate only in differentiated squamous epithelia in warts and in epithelial raft cultures grown at the medium-air interface. Virus-encoded and host transcription factors are thought to be responsible for repressing the viral enhancer and promoter located within the upstream regulatory region (URR) in the undifferentiated basal and parabasal cells while up-regulating their activities in the differentiated spinous cells. Using recombinant retroviruses, we acutely transduced neonatal foreskin keratinocytes (PHKs) with a lacZ reporter gene driven by the wild-type URR of the low-risk HPV type 11 or by a URR with individual mutations in seven promoter-proximal elements, some of which have not been characterized previously. Beta-galactosidase activities were detected in the submerged, proliferating PHKs and also in the differentiated spinous cells, but not in the steady-state proliferating basal cells, of stratified raft cultures. In particular, mutation of an Oct1, an Sp1, or a previously unknown promoter-proximal AP1 site severely reduced the reporter activity, whereas mutation of either of two NF1 sites flanking the Oct1 site had no effect. These results demonstrate changes in cellular transcription factor profiles under different culture conditions and begin to characterize the naturally differentiation-dependent activation of the URR. They provide one molecular explanation for the patterns of HPV expression in warts and help validate epithelial raft cultures as an important experimental system for genetic dissection of HPV regulatory elements.
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Affiliation(s)
- W Zhao
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, 35294-0005, USA
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11
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Andersen B, Hariri A, Pittelkow MR, Rosenfeld MG. Characterization of Skn-1a/i POU domain factors and linkage to papillomavirus gene expression. J Biol Chem 1997; 272:15905-13. [PMID: 9188490 DOI: 10.1074/jbc.272.25.15905] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Tissue-restricted POU domain transcription factors, which bind octamer or octamer-like gene sequences, play roles in cellular differentiation and the development of several organs. We have previously identified a POU domain gene, Skn-1a/i, expressed primarily in epidermis, that encodes at least two products through alternative splicing. One of these, Skn-1a, acts as a transcriptional activator, and the other, Skn-1i, contains an inhibitory domain in the NH2 terminus, which prevents DNA-binding in vitro and transcriptional activation in vivo. We now demonstrate that when Skn-1i is expressed in eukaryotic cells it can bind to an octamer site, suggesting that in vivo cellular factors modulate the activity of the inhibitory domain to permit DNA-binding. Yet the inhibitory domain does not allow transactivation by Skn-1i or by a heterologous transactivator containing this domain in cis. Furthermore, we demonstrate that Skn-1a, Tst-1, and Oct-1 are the major octamer-binding proteins in epidermis. Since Skn-1a is primarily expressed in suprabasal cells of the epidermis, we have tested its possible role in the regulation of epidermal papillomaviruses. In transient transfection assays, Skn-1a and Tst-1 can activate the long control region of the epidermis-specific human papillomavirus 1A (HPV-1A). Consistent with these in vivo transcription data, in vitro DNA binding studies identify three octamer-like sites, which are capable of binding Skn-1a, in the HPV-1A long control region. Mutations of all three octamer-like sites prevent transactivation by Skn-1a in transient transfection assays. Taken together, these results provide evidence that Skn-1a and Tst-1 may provide a molecular link between HPV gene expression and epidermal differentiation.
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Affiliation(s)
- B Andersen
- Division of Endocrinology and Metabolism, School and Department of Medicine, University of California at San Diego, La Jolla, California 92037-0648, USA
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12
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Liu YZ, Latchman DS. The octamer-binding proteins Oct-1 and Oct-2 repress the HIV long terminal repeat promoter and its transactivation by Tat. Biochem J 1997; 322 ( Pt 1):155-8. [PMID: 9078256 PMCID: PMC1218171 DOI: 10.1042/bj3220155] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Although the HIV-1 long terminal repeat (LTR) contains four potential binding sites for the octamer-binding protein, Oct-1, which is known to interact with the HIV-1 Tat protein, the effect of the Oct-1 factor on HIV LTR-driven gene expression has not previously been reported. We show here that both Oct-1, and to a lesser extent the related Oct-2 protein, can repress both the basal activity of the HIV-1 LTR and its transactivation by Tat. These effects are still observed with an HIV LTR construct containing only a single octamer-binding site located between the TATA box and the transcriptional start site. The stronger inhibitory effect of Oct-1 on both these promoters is dependent upon its C-terminal region which cannot be effectively replaced by the equivalent region of Oct-2. These effects are discussed in terms of the regulation of HIV LTR activity in different cell types and in response to T-cell activation.
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Affiliation(s)
- Y Z Liu
- Department of Molecular Pathology, University College London Medical School, U.K
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13
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van Leeuwen HC, Rensen M, van der Vliet PC. The Oct-1 POU homeodomain stabilizes the adenovirus preinitiation complex via a direct interaction with the priming protein and is displaced when the replication fork passes. J Biol Chem 1997; 272:3398-405. [PMID: 9013582 DOI: 10.1074/jbc.272.6.3398] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Initiation of adenovirus DNA replication is strongly enhanced by two cellular transcription factors, NFI and Oct-1, which bind to the auxiliary origin and tether the viral precursor terminal protein-DNA polymerase (pTP.pol) complex to the core origin. NFI acts through a direct contact with the DNA polymerase, but the mode of action of Oct 1 is unknown. Employing glutathione S-transferase-POU pull-down assays and protein affinity chromatography, we have established that the POU domain contacts pTP rather than pol. The POU homeodomain is responsible for this interaction. The protein-protein contacts lead to increased binding of pTP-pol to the core origin, which is caused by a reduced off-rate. The enhanced formation of a pTP.pol.POU complex on the origin correlates with stimulation of replication. Using an immobilized replication system, we have studied the kinetics of dissociation of the Oct-1 POU domain during replication. In contrast to NFI, which dissociates very early in initiation, Oct-1 dissociates only when the binding site is rendered single-stranded upon translocation of the replication fork. Our data indicate that NFI and Oct-1 enhance initiation synergistically by touching different targets in the preinitiation complex and dissociate independently after initiation.
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Affiliation(s)
- H C van Leeuwen
- Laboratory for Physiological Chemistry, Utrecht University, Stratenum, P. O. Box 80042, 3508 TA Utrecht, The Netherlands
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14
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The opposite and antagonistic effects of the closely related POU family transcription factors Brn-3a and Brn-3b on the activity of a target promoter are dependent on differences in the POU domain. Mol Cell Biol 1994. [PMID: 7935408 DOI: 10.1128/mcb.14.10.6907] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The Brn-3a, Brn-3b, and Brn-3c POU family transcription factors are closely related to one another and are members of the group IV subfamily of POU factors. Here we show that despite this close relationship, the factors have different effects on the activity of a target promoter: Brn-3a and Brn-3c stimulate the promoter whereas Brn-3b represses it. Moreover, Brn-3b can antagonize the stimulatory effect of Brn-3a on promoter activity and can also inhibit promoter activation by the Oct-2.1 POU factor. The difference in the transactivation activities of Brn-3a and Brn-3b is dependent upon the C-terminal region containing the POU domain of the two proteins, since exchange of this domain between the two factors converts Brn-3a into a repressor and Brn-3b into an activator.
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15
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Morris PJ, Theil T, Ring CJ, Lillycrop KA, Moroy T, Latchman DS. The opposite and antagonistic effects of the closely related POU family transcription factors Brn-3a and Brn-3b on the activity of a target promoter are dependent on differences in the POU domain. Mol Cell Biol 1994; 14:6907-14. [PMID: 7935408 PMCID: PMC359221 DOI: 10.1128/mcb.14.10.6907-6914.1994] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
The Brn-3a, Brn-3b, and Brn-3c POU family transcription factors are closely related to one another and are members of the group IV subfamily of POU factors. Here we show that despite this close relationship, the factors have different effects on the activity of a target promoter: Brn-3a and Brn-3c stimulate the promoter whereas Brn-3b represses it. Moreover, Brn-3b can antagonize the stimulatory effect of Brn-3a on promoter activity and can also inhibit promoter activation by the Oct-2.1 POU factor. The difference in the transactivation activities of Brn-3a and Brn-3b is dependent upon the C-terminal region containing the POU domain of the two proteins, since exchange of this domain between the two factors converts Brn-3a into a repressor and Brn-3b into an activator.
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Affiliation(s)
- P J Morris
- Department of Molecular Pathology, University College London Medical School, United Kingdom
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16
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Budhram-Mahadeo V, Theil T, Morris PJ, Lillycrop KA, Moroy T, Latchman DS. The DNA target site for the Brn-3 POU family transcription factors can confer responsiveness to cyclic AMP and removal of serum in neuronal cells. Nucleic Acids Res 1994; 22:3092-8. [PMID: 8065921 PMCID: PMC310280 DOI: 10.1093/nar/22.15.3092] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
The POU factors Brn-3a and Brn-3b are closely related transcription factors which are expressed in neuronal cells. The levels of the transcripts encoding these factors are regulated in opposite directions in neuronal cells by specific cellular signalling pathways with dibutyryl cyclic AMP treatment and serum removal enhancing the level of Brn-3a and reducing the level of Brn-3b expression. This opposite expression pattern is paralleled by the ability of Brn-3a to specifically transactivate a target promoter bearing its DNA binding site whereas this promoter is repressed by Brn-3b. As predicted from these observations this target promoter is strongly activated by serum removal or addition of dibutyryl cyclic AMP. Therefore changes in Brn-3a and b expression can have a functional effect on promoter activity indicating that Brn-3a and Brn-3b can regulate gene expression via a specific binding site in response to the activation of specific cellular signalling pathways. The reasons for the differences in activity between these two related factors and their role in regulating gene activity in the nervous system are discussed.
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Affiliation(s)
- V Budhram-Mahadeo
- Department of Molecular Pathology, University College London Medical School, UK
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17
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Dong G, Broker TR, Chow LT. Human papillomavirus type 11 E2 proteins repress the homologous E6 promoter by interfering with the binding of host transcription factors to adjacent elements. J Virol 1994; 68:1115-27. [PMID: 8289341 PMCID: PMC236550 DOI: 10.1128/jvi.68.2.1115-1127.1994] [Citation(s) in RCA: 109] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
The E6 promoter of human papillomaviruses (HPVs) trophic for epithelia for the lower genital tract and the upper respiratory tract is regulated in vitro by homologous and heterologous papillomaviral E2 proteins that bind to a consensus responsive sequence (E2-RS) ACCN6GGT. When HPV type 11 (HPV-11) expression is examined in epithelial cell lines, the HPV-11 E2-C protein, which lacks the amino-terminal transactivating domain of the full-length E2 protein, invariably represses the homologous viral E6 promoter. In contrast, when the novel constitutive enhancer (CE) CE II is deleted, not only is the basal promoter activity much reduced, it is further repressed by the intact HPV-11 E2 protein (M. T. Chin, T. R. Broker, and L. T. Chow, J. Virol. 63:2967-2976, 1989). Here, we demonstrated that, when expressed from a stronger surrogate promoter, the HPV-11 E2 protein represses the E6 promoter effectively, regardless of CE II. By performing systematic mutational analyses of the four highly conserved copies of the HPV-11 E2-RS and of the adjacent enhancer-promoter elements, we show that the furthest upstream, promoter-distal E2-RS copy 1 plays no apparent role in E6 promoter regulation. Repression by the homologous HPV-11 E2 proteins is mediated through each of the three promoter-proximal copies of the E2-RS, but the presence of CE II abrogates the full-length E2 protein repression exerted at E2-RS copy 2. Repression is alleviated when the two (for E2) or three (for E2-C) promoter-proximal copies of E2-RS are mutated. We specifically demonstrate that repression exerted at E2-RS 3 is due to preclusion of binding of the host transcription factor Sp1 or Sp1-like proteins to a nonconsensus sequence AGGAGG located 1 bp upstream of the tandem E2 protein binding sites 3 and 4. A 3-bp insertion between the adjacent Sp1 and E2-RS 3 sites permits both Sp1 and E2 proteins to bind, with a concomitant relief of E2-RS 3-mediated repression. Similar mutational analyses show that proteins that bind to the GT-1 motif near the upstream E2-RS 2 help abrogate repression by the E2 protein in the presence of CE II. The implications of these results with respect to the viral infectious cycle and during viral oncogenesis are discussed.
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Affiliation(s)
- G Dong
- Department of Biochemistry, University of Rochester School of Medicine and Dentistry, New York 14642
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Morris PJ, Ring CJ, Lillycrop KA, Latchman DS. Transactivation of the human papilloma virus 16 octamer motif by the octamer binding protein Oct-2 requires both the N and C terminal activation domains. Nucleic Acids Res 1993; 21:4506-10. [PMID: 8233784 PMCID: PMC311182 DOI: 10.1093/nar/21.19.4506] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
The upstream regulatory region (URR) of the human papillomaviruses HPV16 and 18 contains a sequence with a seven out of eight base match to the consensus binding site for octamer binding transcription factors. This motif acts as a target for repression by the Oct-1 transcription factor and therefore inhibits promoter activity in non-cervical cells expressing only Oct-1. In contrast the HPV octamer motif activates promoter activity in cervical cells. Here we show that cervical cells express the activating form of the Oct-2 transcription factor, Oct 2.1 and that this factor can transactivate promoter activity via the HPV16 octamer. This effect is dependent upon both the N and C-terminal activation domains of Oct-2. The expression of specific octamer binding proteins such as Oct-2 in cervical cells thus allows the HPV16 motif to produce opposite effects on gene expression in cervical and non-cervical cells suggesting that it may play a role in the cervical specificity of URR driven gene expression.
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Affiliation(s)
- P J Morris
- Division of Molecular Pathology, University College London Medical School, UK
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Tverberg L, Russo A. Regulation of the calcitonin/calcitonin gene-related peptide gene by cell-specific synergy between helix-loop-helix and octamer-binding transcription factors. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(18)82346-8] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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Morris PJ, Dent CL, Ring CJ, Latchman DS. The octamer binding site in the HPV16 regulatory region produces opposite effects on gene expression in cervical and non-cervical cells. Nucleic Acids Res 1993; 21:1019-23. [PMID: 8383834 PMCID: PMC309238 DOI: 10.1093/nar/21.4.1019] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
The upstream regulatory region (URR) of the tumorigenic human papillomaviruses HPV 16 and 18 contains an octamer binding site which is located adjacent to a binding site for the ubiquitous transcription factor NFI. The octamer site binds both the constitutively expressed transcription factor Oct-1 and a novel cervical octamer binding protein. In contrast the URR of the non-tumorigenic viruses HPV6 and HPV11 lacks the octamer binding site although the adjacent NFI site is conserved. Inactivation of the octamer binding site results in a higher level of gene expression in cells which contain only Oct-1 and a lower level in cells containing the cervical octamer binding protein indicating that that whilst Oct-1 binding reduces promoter activity, the cervical protein increases it. In agreement with this, over-expression of Oct-1 reduces the level of gene activity directed by this region of the HPV 16/18 URR and inhibits its activation by NFI whilst having no effect on the corresponding region of the HPV 6/11 URR. The significance of these effects is discussed in terms of the cervical-specific activity of the HPV16/18 URR and its role in HPV-mediated transformation.
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Affiliation(s)
- P J Morris
- Department of Biochemistry, University College London School of Medicine, UK
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Jang KL, Latchman DS. The herpes simplex virus immediate-early protein ICP27 stimulates the transcription of cellular Alu repeated sequences by increasing the activity of transcription factor TFIIIC. Biochem J 1992; 284 ( Pt 3):667-73. [PMID: 1320373 PMCID: PMC1132590 DOI: 10.1042/bj2840667] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Infection with herpes simplex virus (HSV) results in an increase in the transcription of the endogenous Alu repeated sequence by RNA polymerase III. This effect is also observed in uninfected cells stably transformed with a plasmid expressing the HSV immediate-early protein ICP27 or in cells transfected with the gene encoding this protein. Both uninfected cells expressing ICP27 and cells infected with virus producing functional ICP27 display increased activity of the cellular transcription factor TFIIIC when compared with untreated cells. This increase is not observed, however, in cells infected with a mutant strain of virus which does not produce ICP27. Hence ICP27 induces elevated Alu transcription by activating transcription factor TFIIIC, which is the limiting factor for such transcription. This is the first report of increased activity of a cellular transcription factor during HSV infection, when most cellular gene activity is inhibited.
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Affiliation(s)
- K L Jang
- Department of Biochemistry, University College and Middlesex School of Medicine, London, U.K
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