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Jacques CN, Favero DS, Kawamura A, Suzuki T, Sugimoto K, Neff MM. SUPPRESSOR OF PHYTOCHROME B-4 #3 reduces the expression of PIF-activated genes and increases expression of growth repressors to regulate hypocotyl elongation in short days. BMC PLANT BIOLOGY 2022; 22:399. [PMID: 35965321 PMCID: PMC9377115 DOI: 10.1186/s12870-022-03737-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/21/2021] [Accepted: 06/24/2022] [Indexed: 06/15/2023]
Abstract
SUPPRESSOR OF PHYTOCHROME B-4 #3 (SOB3) is a member of the AT-HOOK MOTIF CONTAINING NUCLEAR LOCALIZED (AHL) family of transcription factors that are involved in light-mediated growth in Arabidopsis thaliana, affecting processes such as hypocotyl elongation. The majority of the research on the AHLs has been conducted in continuous light. However, there are unique molecular events that promote growth in short days (SD) compared to constant light conditions. Therefore, we investigated how AHLs affect hypocotyl elongation in SD. Firstly, we observed that AHLs inhibit hypocotyl growth in SD, similar to their effect in constant light. Next, we identified AHL-regulated genes in SD-grown seedlings by performing RNA-seq in two sob3 mutants at different time points. Our transcriptomic data indicate that PHYTOCHROME INTERACTING FACTORS (PIFs) 4, 5, 7, and 8 along with PIF-target genes are repressed by SOB3 and/or other AHLs. We also identified PIF target genes that are repressed and have not been previously described as AHL-regulated, including PRE1, PIL1, HFR1, CDF5, and XTR7. Interestingly, our RNA-seq data also suggest that AHLs activate the expression of growth repressors to control hypocotyl elongation, such as HY5 and IAA17. Notably, many growth-regulating and other genes identified from the RNA-seq experiment were differentially regulated between these two sob3 mutants at the time points tested. Surprisingly, our ChIP-seq data suggest that SOB3 mostly binds to similar genes throughout the day. Collectively, these data suggest that AHLs affect gene expression in a time point-specific manner irrespective of changes in binding to DNA throughout SD.
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Affiliation(s)
- Caitlin N Jacques
- RIKEN Center for Sustainable Resource Science, Yokohama, Kanagawa, 230-0045, Japan
- Department of Crops and Soil Sciences, Washington State University, Pullman, WA, 99164, USA
- Molecular Plant Sciences Graduate Program, Washington State University, Pullman, WA, 99164, USA
| | - David S Favero
- RIKEN Center for Sustainable Resource Science, Yokohama, Kanagawa, 230-0045, Japan.
| | - Ayako Kawamura
- RIKEN Center for Sustainable Resource Science, Yokohama, Kanagawa, 230-0045, Japan
| | - Takamasa Suzuki
- Department of Biological Chemistry, College of Biosciences and Biotechnology, Chubu University, Kasugai, Aichi, 487-8501, Japan
| | - Keiko Sugimoto
- RIKEN Center for Sustainable Resource Science, Yokohama, Kanagawa, 230-0045, Japan
- Department of Biological Sciences, The University of Tokyo, Tokyo, 119-0033, Japan
| | - Michael M Neff
- Department of Crops and Soil Sciences, Washington State University, Pullman, WA, 99164, USA.
- Molecular Plant Sciences Graduate Program, Washington State University, Pullman, WA, 99164, USA.
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Nizamuddin S, Koidl S, Bhuiyan T, Werner TV, Biniossek ML, Bonvin AMJJ, Lassmann S, Timmers HT. Integrating quantitative proteomics with accurate genome profiling of transcription factors by greenCUT&RUN. Nucleic Acids Res 2021; 49:e49. [PMID: 33524153 PMCID: PMC8136828 DOI: 10.1093/nar/gkab038] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2020] [Revised: 01/08/2021] [Accepted: 01/16/2021] [Indexed: 11/14/2022] Open
Abstract
Genome-wide localization of chromatin and transcription regulators can be detected by a variety of techniques. Here, we describe a novel method ‘greenCUT&RUN’ for genome-wide profiling of transcription regulators, which has a very high sensitivity, resolution, accuracy and reproducibility, whilst assuring specificity. Our strategy begins with tagging of the protein of interest with GFP and utilizes a GFP-specific nanobody fused to MNase to profile genome-wide binding events. By using a GFP-nanobody the greenCUT&RUN approach eliminates antibody dependency and variability. Robust genomic profiles were obtained with greenCUT&RUN, which are accurate and unbiased towards open chromatin. By integrating greenCUT&RUN with nanobody-based affinity purification mass spectrometry, ‘piggy-back’ DNA binding events can be identified on a genomic scale. The unique design of greenCUT&RUN grants target protein flexibility and yields high resolution footprints. In addition, greenCUT&RUN allows rapid profiling of mutants of chromatin and transcription proteins. In conclusion, greenCUT&RUN is a widely applicable and versatile genome-mapping technique.
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Affiliation(s)
- Sheikh Nizamuddin
- Department of Urology, Medical Center-University of Freiburg, 79016 Freiburg, Germany.,German Cancer Consortium (DKTK) partner site Freiburg, German Cancer Research Center (DKFZ), 69120 Heidelberg, Germany
| | - Stefanie Koidl
- Department of Urology, Medical Center-University of Freiburg, 79016 Freiburg, Germany.,German Cancer Consortium (DKTK) partner site Freiburg, German Cancer Research Center (DKFZ), 69120 Heidelberg, Germany
| | - Tanja Bhuiyan
- Department of Urology, Medical Center-University of Freiburg, 79016 Freiburg, Germany.,German Cancer Consortium (DKTK) partner site Freiburg, German Cancer Research Center (DKFZ), 69120 Heidelberg, Germany
| | - Tamara V Werner
- German Cancer Consortium (DKTK) partner site Freiburg, German Cancer Research Center (DKFZ), 69120 Heidelberg, Germany.,Institute for Surgical Pathology, Medical Center-University of Freiburg, 79016 Freiburg, Germany
| | - Martin L Biniossek
- Institute for Molecular Medicine and Cell Research, Medical Center-University of Freiburg, 79016 Freiburg, Germany
| | - Alexandre M J J Bonvin
- Bijvoet Centre for Biomolecular Research, Faculty of Science - Chemistry, Utrecht University, Utrecht 3584CH, the Netherlands
| | - Silke Lassmann
- German Cancer Consortium (DKTK) partner site Freiburg, German Cancer Research Center (DKFZ), 69120 Heidelberg, Germany.,Institute for Surgical Pathology, Medical Center-University of Freiburg, 79016 Freiburg, Germany
| | - HThMarc Timmers
- Department of Urology, Medical Center-University of Freiburg, 79016 Freiburg, Germany.,German Cancer Consortium (DKTK) partner site Freiburg, German Cancer Research Center (DKFZ), 69120 Heidelberg, Germany
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3
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Polansky H, Schwab H. Dynamics of sequestering the limiting p300/CBP, viral cis-regulatory elements, and disease. J Biosci 2020. [DOI: 10.1007/s12038-020-00051-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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4
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Burley M, Roberts S, Parish JL. Epigenetic regulation of human papillomavirus transcription in the productive virus life cycle. Semin Immunopathol 2020; 42:159-171. [PMID: 31919577 PMCID: PMC7174255 DOI: 10.1007/s00281-019-00773-0] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2019] [Accepted: 11/08/2019] [Indexed: 12/13/2022]
Abstract
Human papillomaviruses (HPV) are a large family of viruses which contain a circular, double-stranded DNA genome of approximately 8000 base pairs. The viral DNA is chromatinized by the recruitment of cellular histones which are subject to host cell-mediated post-translational epigenetic modification recognized as an important mechanism of virus transcription regulation. The HPV life cycle is dependent on the terminal differentiation of the target cell within epithelia-the keratinocyte. The virus life cycle begins in the undifferentiated basal compartment of epithelia where the viral chromatin is maintained in an epigenetically repressed state, stabilized by distal chromatin interactions between the viral enhancer and early gene region. Migration of the infected keratinocyte towards the surface of the epithelium induces cellular differentiation which disrupts chromatin looping and stimulates epigenetic remodelling of the viral chromatin. These epigenetic changes result in enhanced virus transcription and activation of the virus late promoter facilitating transcription of the viral capsid proteins. In this review article, we discuss the complexity of virus- and host-cell-mediated epigenetic regulation of virus transcription with a specific focus on differentiation-dependent remodelling of viral chromatin during the HPV life cycle.
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Affiliation(s)
- Megan Burley
- College of Medical and Dental Sciences, Institute of Cancer and Genomic Sciences, University of Birmingham, B152TT, Birmingham, UK
| | - Sally Roberts
- College of Medical and Dental Sciences, Institute of Cancer and Genomic Sciences, University of Birmingham, B152TT, Birmingham, UK
| | - Joanna L Parish
- College of Medical and Dental Sciences, Institute of Cancer and Genomic Sciences, University of Birmingham, B152TT, Birmingham, UK.
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He H, Lai Y, Hao Y, Liu Y, Zhang Z, Liu X, Guo C, Zhang M, Zhou H, Wang N, Luo XG, Huo L, Ma W, Zhang TC. Selective p300 inhibitor C646 inhibited HPV E6-E7 genes, altered glucose metabolism and induced apoptosis in cervical cancer cells. Eur J Pharmacol 2017; 812:206-215. [PMID: 28619596 DOI: 10.1016/j.ejphar.2017.06.005] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2017] [Revised: 05/29/2017] [Accepted: 06/07/2017] [Indexed: 11/27/2022]
Abstract
High risk HPV infection is a causative factor of cervical cancer. The constitutive expression of HPV E6-E7 genes is important for the maintenance of cancer phenotypes. The cellular transcription co-activator p300 plays a crucial role in the regulation of HPV genes thus it was targeted for the inhibition of HPV-associated cervical cancer. In the present study, HPV positive cervical cells were treated with C646, a selective inhibitor of p300, to investigate its influence on HPV E6-E7 expression and cancer cell growth. Results of RT-qPCR, Western-blot and promoter activity assays showed that C646 inhibited the transcription of HPV E6-E7, which was accompanied with the accumulation of p53 protein. Meanwhile, cell proliferation was suppressed, glucose metabolism was disrupted and apoptosis was induced via the intrinsic pathway. Generally, the anti-cervical cancer potential of C646 was demonstrated and a novel mechanism was proposed in this study.
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Affiliation(s)
- Hongpeng He
- Key Laboratory of Industrial Microbiology, Ministry of Education and Tianjin City, College of Biotechnology, Tianjin University of Science and Technology, Tianjin 300457, PR China
| | - Yongwei Lai
- Key Laboratory of Industrial Microbiology, Ministry of Education and Tianjin City, College of Biotechnology, Tianjin University of Science and Technology, Tianjin 300457, PR China
| | - Yunpeng Hao
- Key Laboratory of Industrial Microbiology, Ministry of Education and Tianjin City, College of Biotechnology, Tianjin University of Science and Technology, Tianjin 300457, PR China
| | - Yupeng Liu
- Key Laboratory of Industrial Microbiology, Ministry of Education and Tianjin City, College of Biotechnology, Tianjin University of Science and Technology, Tianjin 300457, PR China
| | - Zijiang Zhang
- Key Laboratory of Industrial Microbiology, Ministry of Education and Tianjin City, College of Biotechnology, Tianjin University of Science and Technology, Tianjin 300457, PR China
| | - Xiang Liu
- Key Laboratory of Industrial Microbiology, Ministry of Education and Tianjin City, College of Biotechnology, Tianjin University of Science and Technology, Tianjin 300457, PR China
| | - Chenhong Guo
- Key Laboratory of Industrial Microbiology, Ministry of Education and Tianjin City, College of Biotechnology, Tianjin University of Science and Technology, Tianjin 300457, PR China
| | - Mengmeng Zhang
- Key Laboratory of Industrial Microbiology, Ministry of Education and Tianjin City, College of Biotechnology, Tianjin University of Science and Technology, Tianjin 300457, PR China
| | - Hao Zhou
- Key Laboratory of Industrial Microbiology, Ministry of Education and Tianjin City, College of Biotechnology, Tianjin University of Science and Technology, Tianjin 300457, PR China
| | - Nan Wang
- Key Laboratory of Industrial Microbiology, Ministry of Education and Tianjin City, College of Biotechnology, Tianjin University of Science and Technology, Tianjin 300457, PR China
| | - Xue-Gang Luo
- Key Laboratory of Industrial Microbiology, Ministry of Education and Tianjin City, College of Biotechnology, Tianjin University of Science and Technology, Tianjin 300457, PR China
| | - Lihong Huo
- Key Laboratory of Industrial Microbiology, Ministry of Education and Tianjin City, College of Biotechnology, Tianjin University of Science and Technology, Tianjin 300457, PR China
| | - Wenjian Ma
- Key Laboratory of Industrial Microbiology, Ministry of Education and Tianjin City, College of Biotechnology, Tianjin University of Science and Technology, Tianjin 300457, PR China
| | - Tong-Cun Zhang
- Key Laboratory of Industrial Microbiology, Ministry of Education and Tianjin City, College of Biotechnology, Tianjin University of Science and Technology, Tianjin 300457, PR China; College of Life Sciences, Wuhan University of Science and Technology, Wuhan 430081, PR China.
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6
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Castillo A, Wang L, Koriyama C, Eizuru Y, Jordan K, Akiba S. A systems biology analysis of the changes in gene expression via silencing of HPV-18 E1 expression in HeLa cells. Open Biol 2015; 4:rsob.130119. [PMID: 25297386 PMCID: PMC4221889 DOI: 10.1098/rsob.130119] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2022] Open
Abstract
Previous studies have reported the detection of a truncated E1 mRNA generated from HPV-18 in HeLa cells. Although it is unclear whether a truncated E1 protein could function as a replicative helicase for viral replication, it would still retain binding sites for potential interactions with different host cell proteins. Furthermore, in this study, we found evidence in support of expression of full-length HPV-18 E1 mRNA in HeLa cells. To determine whether interactions between E1 and cellular proteins play an important role in cellular processes other than viral replication, genome-wide expression profiles of HPV-18 positive HeLa cells were compared before and after the siRNA knockdown of E1 expression. Differential expression and gene set enrichment analysis uncovered four functionally related sets of genes implicated in host defence mechanisms against viral infection. These included the toll-like receptor, interferon and apoptosis pathways, along with the antiviral interferon-stimulated gene set. In addition, we found that the transcriptional coactivator E1A-binding protein p300 (EP300) was downregulated, which is interesting given that EP300 is thought to be required for the transcription of HPV-18 genes in HeLa cells. The observed changes in gene expression produced via the silencing of HPV-18 E1 expression in HeLa cells indicate that in addition to its well-known role in viral replication, the E1 protein may also play an important role in mitigating the host's ability to defend against viral infection.
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Affiliation(s)
- Andres Castillo
- Department of Physiology and The Basic Sciences School, Health Faculty at Universidad del Valle, Cali, Colombia UniValle-Georgia Tech Genome Research Center, Health Faculty at Universidad del Valle, Cali, Colombia Department of Epidemiology and Preventive Medicine, Kagoshima University Graduate School of Medical and Dental Sciences, 8-35-1 Sakuragaoka, Kagoshima 890-8544, Japan Division of Oncogenic and Persistent Viruses, Center for Chronic Viral Diseases, Kagoshima University Graduate School of Medical and Dental Sciences, 8-35-1 Sakuragaoka, Kagoshima 890-8544, Japan
| | - Lu Wang
- UniValle-Georgia Tech Genome Research Center, Health Faculty at Universidad del Valle, Cali, Colombia School of Biology, Georgia Institute of Technology, Atlanta, GA, USA PanAmerican Bioinformatics Institute, Santa Marta, Magdalena, Colombia
| | - Chihaya Koriyama
- Department of Epidemiology and Preventive Medicine, Kagoshima University Graduate School of Medical and Dental Sciences, 8-35-1 Sakuragaoka, Kagoshima 890-8544, Japan
| | - Yoshito Eizuru
- Division of Oncogenic and Persistent Viruses, Center for Chronic Viral Diseases, Kagoshima University Graduate School of Medical and Dental Sciences, 8-35-1 Sakuragaoka, Kagoshima 890-8544, Japan
| | - King Jordan
- UniValle-Georgia Tech Genome Research Center, Health Faculty at Universidad del Valle, Cali, Colombia School of Biology, Georgia Institute of Technology, Atlanta, GA, USA PanAmerican Bioinformatics Institute, Santa Marta, Magdalena, Colombia
| | - Suminori Akiba
- Department of Epidemiology and Preventive Medicine, Kagoshima University Graduate School of Medical and Dental Sciences, 8-35-1 Sakuragaoka, Kagoshima 890-8544, Japan
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7
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He H, Liu X, Wang D, Wang Y, Liu L, Zhou H, Luo X, Wang N, Ji B, Luo Y, Zhang T. SAHA inhibits the transcription initiation of HPV18 E6/E7 genes in HeLa cervical cancer cells. Gene 2014; 553:98-104. [PMID: 25300249 DOI: 10.1016/j.gene.2014.10.007] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2014] [Revised: 09/16/2014] [Accepted: 10/03/2014] [Indexed: 02/03/2023]
Abstract
High risk human papillomavirus (HPV) is a well recognized causative agent of cervical cancer. Suberoylanilide hydroxamic acid (SAHA) is a potential anti-cervical cancer drug; however, its effect on the expression of HPV E6 and E7 genes remains unclear. Here, we show that, in SAHA treated HeLa cells, HPV18 E6 and E7 mRNA and protein levels were reduced, HPV18 promoter activity was decreased, and the association of RNP II with HPV18 promoter was diminished, suggesting that SAHA inhibited the transcription initiation of HPV18 E6 and E7 genes. In SAHA-treated HeLa, although the level of lysine 9-acetylated histone H3 in the whole cell extracts increased obviously, its enrichment on HPV18 promoter was significantly reduced which is correlated with the down-regulation of HPV E6 and E7.
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Affiliation(s)
- Hongpeng He
- Key Laboratory of Industrial Microbiology, Ministry of Education and Tianjin City, College of Biotechnology, Tianjin University of Science and Technology, Tianjin 300457, PR China
| | - Xuena Liu
- Key Laboratory of Industrial Microbiology, Ministry of Education and Tianjin City, College of Biotechnology, Tianjin University of Science and Technology, Tianjin 300457, PR China
| | - Dandan Wang
- Key Laboratory of Industrial Microbiology, Ministry of Education and Tianjin City, College of Biotechnology, Tianjin University of Science and Technology, Tianjin 300457, PR China
| | - Yijie Wang
- Key Laboratory of Industrial Microbiology, Ministry of Education and Tianjin City, College of Biotechnology, Tianjin University of Science and Technology, Tianjin 300457, PR China
| | - Lei Liu
- Key Laboratory of Industrial Microbiology, Ministry of Education and Tianjin City, College of Biotechnology, Tianjin University of Science and Technology, Tianjin 300457, PR China
| | - Hao Zhou
- Key Laboratory of Industrial Microbiology, Ministry of Education and Tianjin City, College of Biotechnology, Tianjin University of Science and Technology, Tianjin 300457, PR China
| | - Xuegang Luo
- Key Laboratory of Industrial Microbiology, Ministry of Education and Tianjin City, College of Biotechnology, Tianjin University of Science and Technology, Tianjin 300457, PR China
| | - Nan Wang
- Key Laboratory of Industrial Microbiology, Ministry of Education and Tianjin City, College of Biotechnology, Tianjin University of Science and Technology, Tianjin 300457, PR China
| | - Bingyan Ji
- School of Basic Medical Sciences, Zhejiang University College of Medicine, #388, YuHangTang Road, Hangzhou, Zhejiang 310058, PR China
| | - Yan Luo
- School of Basic Medical Sciences, Zhejiang University College of Medicine, #388, YuHangTang Road, Hangzhou, Zhejiang 310058, PR China.
| | - Tongcun Zhang
- Key Laboratory of Industrial Microbiology, Ministry of Education and Tianjin City, College of Biotechnology, Tianjin University of Science and Technology, Tianjin 300457, PR China; College of Life Sciences, Wuhan University of Science and Technology, Wuhan 430081, PR China.
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8
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Ozturk N, Singh I, Mehta A, Braun T, Barreto G. HMGA proteins as modulators of chromatin structure during transcriptional activation. Front Cell Dev Biol 2014; 2:5. [PMID: 25364713 PMCID: PMC4207033 DOI: 10.3389/fcell.2014.00005] [Citation(s) in RCA: 105] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2013] [Accepted: 02/07/2014] [Indexed: 01/12/2023] Open
Abstract
High mobility group (HMG) proteins are the most abundant non-histone chromatin associated proteins. HMG proteins bind to DNA and nucleosome and alter the structure of chromatin locally and globally. Accessibility to DNA within chromatin is a central factor that affects DNA-dependent nuclear processes, such as transcription, replication, recombination, and repair. HMG proteins associate with different multi-protein complexes to regulate these processes by mediating accessibility to DNA. HMG proteins can be subdivided into three families: HMGA, HMGB, and HMGN. In this review, we will focus on recent advances in understanding the function of HMGA family members, specifically their role in gene transcription regulation during development and cancer.
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Affiliation(s)
- Nihan Ozturk
- LOEWE Research Group Lung Cancer Epigenetic, Max-Planck-Institute for Heart and Lung Research Bad Nauheim, Germany
| | - Indrabahadur Singh
- LOEWE Research Group Lung Cancer Epigenetic, Max-Planck-Institute for Heart and Lung Research Bad Nauheim, Germany
| | - Aditi Mehta
- LOEWE Research Group Lung Cancer Epigenetic, Max-Planck-Institute for Heart and Lung Research Bad Nauheim, Germany
| | - Thomas Braun
- Department of Cardiac Development and Remodeling, Max-Planck-Institute for Heart and Lung Research Bad Nauheim, Germany
| | - Guillermo Barreto
- LOEWE Research Group Lung Cancer Epigenetic, Max-Planck-Institute for Heart and Lung Research Bad Nauheim, Germany
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Wang WM, Wu SY, Lee AY, Chiang CM. Binding site specificity and factor redundancy in activator protein-1-driven human papillomavirus chromatin-dependent transcription. J Biol Chem 2011; 286:40974-86. [PMID: 21937452 DOI: 10.1074/jbc.m111.290874] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Activator protein-1 (AP-1) regulates diverse gene responses triggered by environmental cues and virus-induced cellular stress. Although many signaling events leading to AP-1 activation have been described, the fundamental features underlying binding site selection and factor recruitment of dimeric AP-1 complexes to their target genes remain mostly uncharacterized. Using recombinant full-length human AP-1 dimers formed between c-Jun and Fos family members (c-Fos, FosB, Fra-1, Fra-2) for DNA binding and transcriptional analysis, we found that each of these AP-1 complex exhibits differential activity for distinct non-consensus AP-1 sites present in human papillomavirus (HPV), and each AP-1 complex is capable of activating transcription from in vitro-reconstituted HPV chromatin in a p300- and acetyl-CoA-dependent manner. Transcription from HPV chromatin requires AP-1-dependent and contact-driven recruitment of p300. Acetylation of dimeric AP-1 complexes by p300 enhances AP-1 binding to DNA. Using a human C-33A cervical cancer-derived cell line harboring the episomal HPV type 11 genome, we illustrate binding site selectivity recognized by c-Jun, JunB, JunD, and various Fos family members in a combinatorial and unique pattern, highlighting the diversity and importance of non-canonical binding site recognition by various AP-1 family proteins.
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Affiliation(s)
- Wei-Ming Wang
- Simmons Comprehensive Cancer Center, Dallas, Texas 75390, USA
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10
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The E2F5 repressor is an activator of E6/E7 transcription and of the S-phase entry in HPV18-associated cells. Oncogene 2010; 29:5061-70. [PMID: 20639900 DOI: 10.1038/onc.2010.246] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
High-risk papillomavirus type 18 (HPV18) is one of the less represented HPV types in low-grade lesions of the anogenital tract, whereas it occupies the second place in cervical cancer, where it can be found in 16% of the cases worldwide, after HPV16 present in 54% of them. These epidemiological data indicate that HPV18 infection is more prone to carcinogenic progression. The main oncogenic proteins, E6 and E7 of HPV18, are functionally comparable to the homologous proteins of the other high-risk viruses, including HPV16. In this work, we investigated the possibility that the higher oncogenic potential of HPV18 might be due to transcriptional regulation of the E6/E7 oncogenes. By comparing the E6/E7 promoter and enhancer sequences of the mucosal HPV genomes, we identified E2F binding sites specific for HPV18. The E2F family of transcription factors contains activators (E2F1-3) and repressors (E2F4-8) that regulate the transcription of S-phase and mitotic genes and thereby have a crucial role in cell-cycle progression. Surprisingly, we identified E2F5 as a direct activator of HPV18 E6/E7 transcription by sequential silencing of E2F members in HeLa cells. In addition, we could show that E2F5 positively regulates S-phase entry in HeLa cells and that this activation of the cell cycle by a member of the E2F repressor family is specific for HPV18-expressing cells. Diverting the function of E2F5 from a cell-cycle repressor into an activator might contribute to the higher oncogenic potential of HPV18 when compared with other high-risk HPV types.
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p300 Expression is Related to High-risk Human Papillomavirus Infections and Severity of Cervical Intraepithelial Neoplasia But Not to Viral or Disease Outcomes in a Longitudinal Setting. Int J Gynecol Pathol 2010; 29:135-45. [DOI: 10.1097/pgp.0b013e3181bccaec] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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12
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Wu W, Wan W, Li ADQ. The nuclear architectural protein HMGA1a triggers receptor-mediated endocytosis. J Cell Biochem 2009; 108:791-801. [PMID: 19739099 DOI: 10.1002/jcb.22281] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
High mobility group proteins A (HMGA), nuclear architectural factors, locate in the cell nuclei and mostly execute gene-regulation function. However, our results reveal that a HMGA member (HMGA1a) has a unique plasma membrane receptor; this receptor specifically binds to HMGA-decorated species, effectively mediates endocytosis, and internalizes extracellular HMGA-functionalized cargoes. Indeed, dyes or nanoparticles labeled with HMGA1a protein readily enter Hela cells. Using a stratagem chemical cross-linker, we covalently bonded the HMGA receptor to the HMGA1a-GFP fusion protein, thus capturing the plasma membrane receptor. Subsequent Western blots and SDS-PAGE gel revealed that the HMGA receptor is a 26-kDa protein. Confocal live-cell microscopic imaging was used to monitor the whole endocytic process, in which the internalized HMGA1a-decorated species are transported by motor proteins on microtubules and eventually arrive at the late endosomes/lysosomes. Cell viability assays also suggested that extracellular HMGA1a protein directly influences the survival ability of Hela cells in a dose-dependent manner, implying versatility of HMGA1a protein and its potent role to suppress cancer cell survivability and to regulate growth.
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Affiliation(s)
- Wuwei Wu
- Department of Chemistry and Center for Materials Research, Washington State University, Pullman, Washington 99164, USA
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13
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You J. Papillomavirus interaction with cellular chromatin. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2009; 1799:192-9. [PMID: 19786128 DOI: 10.1016/j.bbagrm.2009.09.009] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2009] [Revised: 09/14/2009] [Accepted: 09/17/2009] [Indexed: 11/26/2022]
Abstract
High-risk human papillomavirus (HPV) infection is the primary risk factor for cervical cancer. HPVs establish persistent infection by maintaining their genomes as extrachromosomal elements (episomes) that replicate along with host DNA in infected cells. The productive life cycle of HPV is intimately tied to the differentiation program of host squamous epithelium. This review examines the involvement of host chromatin in multiple aspects of the papillomavirus life cycle and the malignant progression of infected host cells. Papillomavirus utilizes host mitotic chromosomes as vehicles for transmitting its genetic materials across the cell cycle. By hitchhiking on host mitotic chromosomes, the virus ensures accurate segregation of the replicated viral episomes to the daughter cells during host cell division. This strategy allows persistent maintenance of the viral episome in the infected cells. In the meantime, the virus subverts the host chromatin-remodeling factors to promote viral transcription and efficient propagation of viral genomes. By associating with the host chromatin, papillomavirus redirects the normal cellular control of chromatin to create a cellular environment conducive to both its own survival and malignant progression of host cells. Comprehensive understanding of HPV-host chromatin interaction will offer new insights into the HPV life cycle as well as chromatin regulation. This virus-host interaction will also provide a paradigm for investigating other episomal DNA tumor viruses that share a similar mechanism for interacting with host chromatin.
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Affiliation(s)
- Jianxin You
- Department of Microbiology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA.
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14
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Optimal transactivation by Epstein-Barr nuclear antigen 1 requires the UR1 and ATH1 domains. J Virol 2009; 83:4227-35. [PMID: 19244333 DOI: 10.1128/jvi.02578-08] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Epstein-Barr nuclear antigen 1 (EBNA1) is essential for Epstein-Barr virus to immortalize naïve B cells. EBNA1 transactivates viral promoters for genes that are necessary for immortalization when it is bound to a cluster of 20 cognate binding sites, termed the family of repeats. A region of EBNA1 from amino acids (aa) 40 to 89, termed linking region 1 (LR1), has been identified previously as being sufficient for transactivation. LR1 contains two domains that are conserved in the EBNA1 orthologs of other gamma herpesviruses. The first of these, termed unique region 1 (UR1), corresponds to aa 65 to 89 of EBNA1. UR1 is necessary for transactivation and contains a conserved recognition site for cyclic AMP-dependent protein kinase (PKA), corresponding to serine 78 of EBNA1. We have pharmacologically modulated PKA activity to determine if PKA controls EBNA1's ability to transactivate. Our results indicate that PKA activators and inhibitors do not affect transactivation by EBNA1. In addition, site-directed mutagenesis demonstrates that transactivation is not influenced by the phosphorylation status of serine 78 in the UR1 domain. The second conserved domain within LR1 is a glycine-arginine repeat, corresponding to aa 40 to 54 of EBNA1. This domain, termed ATH1, functions as an AT-hook, a DNA-binding motif found in architectural transcription factors such as HMGA1a. We demonstrate that deletion of the ATH1 domain decreases EBNA1 transactivation ability, which is consistent with a transcriptional role for ATH1. Furthermore, transactivation is restored when ATH1 is replaced by equivalent AT-hook motifs from HMGA1a. Our data strongly indicate a role for AT-hooks in EBNA1's ability to transactivate, a function necessary for EBV to immortalize naïve B-cells.
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15
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Thierry F. Transcriptional regulation of the papillomavirus oncogenes by cellular and viral transcription factors in cervical carcinoma. Virology 2008; 384:375-9. [PMID: 19064276 DOI: 10.1016/j.virol.2008.11.014] [Citation(s) in RCA: 137] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2008] [Accepted: 11/04/2008] [Indexed: 12/30/2022]
Abstract
Human papillomaviruses (HPV) are small DNA viruses that contain a compact and non-redundant genome. HPV, with the help of only few genes, can achieve a complete vegetative cycle specifically in the epidermal and mucosal keratinocytes. Modification of the host cell transcriptional regulation is one of the major ways to regulate the viral production and maturation. The vegetative cycle of papillomaviruses is linked to terminal differentiation of the epithelium and is dependent on the host cell regulatory networks for transcriptional control. The mucosal high risk HPV16 and HPV18 types have been the main models to explore this transcriptional regulation mainly because they are prevalent in cervical cancer as the best studied virally induced cancers in human. In addition, the availability of cell lines, grown from cervical cancers containing integrated HPV16 or 18, represent versatile in vitro models for transcription studies. We will describe here some aspects of the transcriptional regulation that contribute to cell specificity, the basis of which is not yet fully understood despite efforts of numerous groups during the past two decades. Another specificity of small DNA viruses is the multifunctional characteristics of their regulatory proteins due to extreme genomic constraint. We will describe the role played by the viral E2 proteins in the transcriptional repression of the high risk HPV oncogenes and its implication in cervical cancer.
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16
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Human papilloma virus-dependent HMGA1 expression is a relevant step in cervical carcinogenesis. Neoplasia 2008; 10:773-81. [PMID: 18670638 DOI: 10.1593/neo.08462] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2008] [Revised: 05/12/2008] [Accepted: 05/13/2008] [Indexed: 11/18/2022] Open
Abstract
HMGA1 is a member of a small family of architectural transcription factors involved in the coordinate assembly of multiprotein complexes referred to as enhanceosomes. In addition to their role in cell proliferation, differentiation, and development, high-mobility group proteins of the A type (HMGA) family members behave as transforming protoncogenes either in vitro or in animal models. Recent reports indicated that HMGA1 might counteract p53 pathway and provided an interesting hint on the mechanisms determining HMGA's transforming potential. HMGA1 expression is deregulated in a very large array of human tumors, including cervical cancer, but very limited information is available on the molecular mechanisms leading to HMGA1 deregulation in cancer cells. Here, we report that HMGA1 expression is sustained by human papilloma virus (HPV) E6/E7 proteins in cervical cancer, as demonstrated by either E6/E7 overexpression or by repression through RNA interference. Knocking down HMGA1 expression by means of RNA interference, we also showed that it is involved in cell proliferation and contributes to p53 inactivation in this type of neoplasia. Finally, we show that HMGA1 is necessary for the full expression of HPV18 E6 and E7 oncoproteins thus establishing a positive autoregulatory loop between HPV E6/E7 and HMGA1 expression.
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17
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Valencia-Hernández A, Cuevas-Bennett C, Garrido E. Transcriptional regulation of human papillomavirus type 18 P105 promoter by the co-activator CBP. Intervirology 2008; 50:418-25. [PMID: 18182775 DOI: 10.1159/000112917] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2006] [Accepted: 11/20/2007] [Indexed: 11/19/2022] Open
Abstract
UNLABELLED Human papillomaviruses (HPVs) are the etiological agents of cervical cancer, with HPV-16 and 18 being the representative types of the higher risk group. The expression of the viral genes with transforming activity (E6 and E7) is controlled by the upstream regulatory region (URR), a segment of the viral genome that contains elements recognized by several transcription factors. OBJECTIVE We have analyzed the participation of the cellular co-activator CBP on the transcriptional regulation of the HPV-18 URR. METHODS We generated mutants and 5' end deletion constructs derived from the HPV-18 URR and evaluated their transcriptional activity performing transient co-transfection assays on C-33A cells with a plasmid that over-expresses the co-activator CBP. We also performed quantitative chromatin immunoprecipitation assays to analyze the participation of the co-activator CBP on the HPV-18 P105 promoter. RESULTS Our results demonstrate that in C-33A cells CBP acts as a strong activator of the HPV-18 P105 promoter by a mechanism that depends on the integrity of the SP1-binding site, directly correlating with the acetylation of the histone H3 that is involved in nucleosomal stability. CONCLUSION We propose a mechanism of regulation of the HPV-18 P105 promoter by the cellular co-activator CBP, recruited by the transcription factor SP1.
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Affiliation(s)
- Armando Valencia-Hernández
- Departamento de Genética y Biología Molecular, Centro de Investigación y de Estudios Avanzados del IPN, México, México
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18
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Müller-Schiffmann A, Beckmann J, Steger G. The E6 protein of the cutaneous human papillomavirus type 8 can stimulate the viral early and late promoters by distinct mechanisms. J Virol 2006; 80:8718-28. [PMID: 16912319 PMCID: PMC1563847 DOI: 10.1128/jvi.00250-06] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
The expression of the proteins encoded by human papillomaviruses (HPVs) is tightly linked to the differentiation program of the infected keratinocytes. The late promoter, expressing the structural proteins, becomes activated in the differentiated keratinocytes, while the early promoter is also active in the basal layers. We have shown previously that the viral transcriptional regulator E2 and the cellular coactivator p300 cooperate in activation of gene expression of HPV8, which infects the skin and is associated with epidermodysplasia verruciformis. Here we demonstrate that this activation is further stimulated after overexpression of the E6 oncoprotein of HPV8 (8E6). RNase protection experiments revealed that 8E6 efficiently cooperates with 8E2 and p300 in activation of the late promoter. In addition, the early promoter, which did not respond to 8E2 and/or p300, was stimulated more than fourfold by 8E6. Our data suggest that both promoters are activated via distinct mechanisms, since the activation of the early promoter was achieved by the N-terminal moiety of 8E6; in contrast, its C-terminal half was sufficient for late promoter activation. This was markedly reduced by the deletion of amino acids 132 to 136 of 8E6, which also abolished the binding to p300, indicating that a direct interaction between 8E6 and p300 is involved. Moreover, a 45-amino-acid segment within the C/H3 region of p300 is required for 8E6 to stimulate the coactivator function of p300. Our results demonstrate for the first time that an E6 oncoprotein of HPV directly contributes to the regulation of HPV gene expression.
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19
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Centlivre M, Sommer P, Michel M, Ho Tsong Fang R, Gofflo S, Valladeau J, Schmitt N, Thierry F, Hurtrel B, Wain-Hobson S, Sala M. HIV-1 clade promoters strongly influence spatial and temporal dynamics of viral replication in vivo. J Clin Invest 2005; 115:348-58. [PMID: 15690084 PMCID: PMC546425 DOI: 10.1172/jci22873] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2004] [Accepted: 12/12/2004] [Indexed: 01/25/2023] Open
Abstract
Although the primary determinant of cell tropism is the interaction of viral envelope or capsid proteins with cellular receptors, other viral elements can strongly modulate viral replication. While the HIV-1 promoter is polymorphic for a variety of transcription factor binding sites, the impact of these polymorphisms on viral replication in vivo is not known. To address this issue, we engineered isogenic SIVmac239 chimeras harboring the core promoter/enhancer from HIV-1 clades B, C, and E. Here it is shown that the clade C and E core promoters/enhancers bear a noncanonical activator protein-1 (AP-1) binding site, absent from the corresponding clade B region. Relative ex vivo replication of chimeras was strongly dependent on the tissue culture system used. Notably, in thymic histocultures, replication of the clade C chimera was favored by IL-7 enrichment, which suggests that the clade C polymorphism in the AP-1 and NF-kappaB binding sites is involved. Simultaneous infection of rhesus macaques with the 3 chimeras revealed a strong predominance of the clade C chimera during primary infection. Thereafter, the B chimera dominated in all tissues. These data show that the clade C promoter is particularly adapted to sustain viral replication in primary viremia and that clade-specific promoter polymorphisms constitute a major determinant for viral replication.
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Affiliation(s)
- Mireille Centlivre
- Unité de Rétrovirologie Moléculaire, Unité de Biologie Cellulaire du Noyau, Institut Pasteur, Paris, France
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20
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Centlivre M, Sommer P, Michel M, Fang RHT, Gofflo S, Valladeau J, Schmitt N, Thierry F, Hurtrel B, Wain-Hobson S, Sala M. HIV-1 clade promoters strongly influence spatial and temporal dynamics of viral replication in vivo. J Clin Invest 2005. [DOI: 10.1172/jci200522873] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
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21
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Sgarra R, Rustighi A, Tessari MA, Di Bernardo J, Altamura S, Fusco A, Manfioletti G, Giancotti V. Nuclear phosphoproteins HMGA and their relationship with chromatin structure and cancer. FEBS Lett 2004; 574:1-8. [PMID: 15358530 DOI: 10.1016/j.febslet.2004.08.013] [Citation(s) in RCA: 152] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2004] [Revised: 07/23/2004] [Accepted: 08/02/2004] [Indexed: 01/09/2023]
Abstract
The structural characteristics of the three nuclear phosphoproteins of the high mobility group A family are outlined and related to their participation in chromatin structure alteration in many biological processes such as gene expression, neoplastic transformation, differentiation, and apoptosis. The elevated expression of these proteins in tumor cells and their post-translational modifications, such as phosphorylation, acetylation and methylation, are discussed and suggested as suitable targets for cancer chemotherapy.
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Affiliation(s)
- Riccardo Sgarra
- Dipartimento di Biochimica, Biofisica e Chimica delle Macromolecole, via L. Giorgieri 1, Università di Trieste, 34127 Trieste, Italy
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22
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Dhar A, Hu J, Reeves R, Resar LMS, Colburn NH. Dominant-negative c-Jun (TAM67) target genes: HMGA1 is required for tumor promoter-induced transformation. Oncogene 2004; 23:4466-76. [PMID: 15064752 DOI: 10.1038/sj.onc.1207581] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Activation of the transcription factor AP-1 (activator protein-1) is required for tumor promotion and maintenance of malignant phenotype. A number of AP-1-regulated genes that play a role in tumor progression have been identified. However, AP-1-regulated genes driving tumor induction are yet to be defined. Previous studies have established that expression of a dominant-negative c-Jun (TAM67) inhibits phorbol 12-tetradecanoyl-13-acetate (TPA)-induced AP-1 transactivation as well as transformation in mouse epidermal JB6/P+ cells and tumor promotion in mouse skin carcinogenesis. In this study, we utilized the tumor promotion-sensitive JB6/P+ cells to identify AP-1-regulated TAM67 target genes and to establish causal significance in transformation for one target gene. A 2700 cDNA microarray was queried with RNA from TPA-treated P+ cells with or without TAM67 expression. Under conditions in which TAM expression inhibited TPA-induced transformation, microarray analysis identified a subset of six genes induced by TPA and suppressed by TAM67. One of the identified genes, the high-mobility group protein A1 (Hmga1) is induced by TPA in P+, but not in transformation-resistant P cells. We show that TPA induction of the architectural transcription factor HMGA1 is inhibited by TAM67, is extracellular-signal-regulated kinase (ERK)-activation dependent, and is mediated by AP-1. HMGA1 antisense construct transfected into P+ cells blocked HMGA1 protein expression and inhibited TPA-induced transformation indicating that HMGA1 is required for transformation. HMGA1 is not however sufficient as HMGA1a or HMGA1b overexpression did not confer transformation sensitivity on P- cells. Although HMGA1 expression is ERK dependent, it is not the only ERK-dependent event required for transformation because it does not suffice to rescue ERK-deficient P- cells. Our study shows (a) TAM 67 when it inhibits AP-1 and transformation, targets a relatively small number of genes; (b) HMGA1, a TAM67 target gene, is causally related to transformation and therefore a potentially important target for cancer prevention.
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Affiliation(s)
- Arindam Dhar
- Gene Regulation Section, Laboratory of Cancer Prevention, NCI at Frederick, Frederick, MD 21702-1201, USA.
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23
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Hommura F, Katabami M, Leaner VD, Donninger H, Sumter TF, Resar LM, Birrer MJ. HMG-I/Y Is a c-Jun/Activator Protein-1 Target Gene and Is Necessary for c-Jun–Induced Anchorage-Independent Growth in Rat1a Cells. Mol Cancer Res 2004. [DOI: 10.1158/1541-7786.305.2.5] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Abstract
The transcription complex activator protein-1 (AP-1) plays a role in a diverse number of cellular processes including proliferation, differentiation, and apoptosis. To identify AP-1–responsive target genes, we used a doxycycline-inducible c-Jun system in Rat1a cells. The HMG-I/Y chromatin binding protein was found to be up-regulated by c-Jun. Following induction of c-Jun expression, Rat1a cells under nonadherent growth conditions have sustained HMG-I/Y mRNA expression and 2-fold higher protein than uninduced cells. HMG-I/Y promoter reporter assays show that HMG-I/Y promoter activity increases in the presence of c-Jun expression, and gel mobility shift assays demonstrate that induced c-Jun binds to an AP-1 consensus site at position −1,091 in the HMG-I/Y promoter. Suppression of HMG-I/Y expression by its antisense sequence significantly reduces the ability of c-Jun–overexpressing Rat1a cells to grow in an anchorage-independent fashion. HMG-I/Y transforms Rat1a cells (although the colonies are smaller than that observed for the cells overexpressing c-Jun). Taken together, these results suggest that HMG-I/Y is a direct transcriptional target of c-Jun necessary for c-Jun–induced anchorage-independent growth in Rat1a cells.
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Affiliation(s)
- Fumihiro Hommura
- 1Cell and Cancer Biology Branch, National Cancer Institute, Rockville, Maryland and
| | - Motoo Katabami
- 1Cell and Cancer Biology Branch, National Cancer Institute, Rockville, Maryland and
| | - Virna D. Leaner
- 1Cell and Cancer Biology Branch, National Cancer Institute, Rockville, Maryland and
| | - Howard Donninger
- 1Cell and Cancer Biology Branch, National Cancer Institute, Rockville, Maryland and
| | - Takita F. Sumter
- 2Departments of Pediatrics and Oncology, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Linda M.S. Resar
- 2Departments of Pediatrics and Oncology, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Michael J. Birrer
- 1Cell and Cancer Biology Branch, National Cancer Institute, Rockville, Maryland and
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