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Raicu AM, Castanheira P, Arnosti DN. Retinoblastoma protein activity revealed by CRISPRi study of divergent Rbf1 and Rbf2 paralogs. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.05.19.541454. [PMID: 37293052 PMCID: PMC10245722 DOI: 10.1101/2023.05.19.541454] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Retinoblastoma tumor suppressor proteins regulate the key transition from G1 to S phase of the cell cycle. The mammalian Rb family comprises Rb, p107, and p130, with overlapping and unique roles in gene regulation. Drosophila experienced an independent gene duplication event, leading to the Rbf1 and Rbf2 paralogs. To uncover the significance of paralogy in the Rb family, we used CRISPRi. We engineered dCas9 fusions to Rbf1 and Rbf2, and deployed them to gene promoters in developing Drosophila tissue to study their relative impacts on gene expression. On some genes, both Rbf1 and Rbf2 mediate potent repression, in a highly distance-dependent manner. In other cases, the two proteins have different effects on phenotype and gene expression, indicating different functional potential. In a direct comparison of Rb activity on endogenous genes and transiently transfected reporters, we found that only qualitative, but not key quantitative aspects of repression were conserved, indicating that the native chromatin environment generates context-specific effects of Rb activity. Our study uncovers the complexity of Rb-mediated transcriptional regulation in a living organism, which is clearly impacted by the different promoter landscapes and the evolution of the Rb proteins themselves.
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Affiliation(s)
- Ana-Maria Raicu
- Cell and Molecular Biology Program, Michigan State University, East Lansing, MI
| | - Patricia Castanheira
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI
| | - David N Arnosti
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI
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2
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Vu HT, Kaur H, Kies KR, Starks RR, Tuteja G. Identifying novel regulators of placental development using time-series transcriptome data. Life Sci Alliance 2023; 6:6/2/e202201788. [PMID: 36622342 PMCID: PMC9748866 DOI: 10.26508/lsa.202201788] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2022] [Revised: 11/21/2022] [Accepted: 11/22/2022] [Indexed: 12/15/2022] Open
Abstract
The placenta serves as a connection between the mother and the fetus during pregnancy, providing the fetus with oxygen, nutrients, and growth hormones. However, the regulatory mechanisms and dynamic gene interaction networks underlying early placental development are understudied. Here, we generated RNA-sequencing data from mouse fetal placenta at embryonic days 7.5, 8.5, and 9.5 to identify genes with timepoint-specific expression, then inferred gene interaction networks to analyze highly connected network modules. We determined that timepoint-specific gene network modules were associated with distinct developmental processes, and with similar expression profiles to specific human placental cell populations. From each module, we identified hub genes and their direct neighboring genes, which were predicted to govern placental functions. We confirmed that four novel candidate regulators identified through our analyses regulate cell migration in the HTR-8/SVneo cell line. Overall, we predicted several novel regulators of placental development expressed in specific placental cell types using network analysis of bulk RNA-sequencing data. Our findings and analysis approaches will be valuable for future studies investigating the transcriptional landscape of early development.
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Affiliation(s)
- Ha Th Vu
- Genetics, Development, and Cell Biology, Iowa State University, Ames, IA, USA.,Bioinformatics and Computational Biology, Iowa State University, Ames, IA, USA
| | - Haninder Kaur
- Genetics, Development, and Cell Biology, Iowa State University, Ames, IA, USA
| | - Kelby R Kies
- Genetics, Development, and Cell Biology, Iowa State University, Ames, IA, USA.,Bioinformatics and Computational Biology, Iowa State University, Ames, IA, USA
| | - Rebekah R Starks
- Genetics, Development, and Cell Biology, Iowa State University, Ames, IA, USA.,Bioinformatics and Computational Biology, Iowa State University, Ames, IA, USA
| | - Geetu Tuteja
- Genetics, Development, and Cell Biology, Iowa State University, Ames, IA, USA .,Bioinformatics and Computational Biology, Iowa State University, Ames, IA, USA
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3
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Integrated Analysis of Cancer Tissue and Vitreous Humor from Retinoblastoma Eyes Reveals Unique Tumor-Specific Metabolic and Cellular Pathways in Advanced and Non-Advanced Tumors. Cells 2022; 11:cells11101668. [PMID: 35626705 PMCID: PMC9139581 DOI: 10.3390/cells11101668] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2022] [Revised: 05/10/2022] [Accepted: 05/11/2022] [Indexed: 12/16/2022] Open
Abstract
Retinoblastoma (Rb) is a pediatric intraocular malignancy that is proposed to originate from maturing cone cell precursors in the developing retina. The molecular mechanisms underlying the biological and clinical behaviors are important to understand in order to improve the management of advanced-stage tumors. While the genetic causes of Rb are known, an integrated understanding of the gene expression and metabolic processes in tumors of human eyes is deficient. By integrating transcriptomic profiling from tumor tissues and metabolomics from tumorous eye vitreous humor samples (with healthy, age-matched pediatric retinae and vitreous samples as controls), we uncover unique functional associations between genes and metabolites. We found distinct gene expression patterns between clinically advanced and non-advanced Rb. Global metabolomic analysis of the vitreous humor of the same Rb eyes revealed distinctly altered metabolites, indicating how tumor metabolism has diverged from healthy pediatric retina. Several key enzymes that are related to cellular energy production, such as hexokinase 1, were found to be reduced in a manner corresponding to altered metabolites; notably, a reduction in pyruvate levels. Similarly, E2F2 was the most significantly elevated E2F family member in our cohort that is part of the cell cycle regulatory circuit. Ectopic expression of the wild-type RB1 gene in the Rb-null Y79 and WERI-Rb1 cells rescued hexokinase 1 expression, while E2F2 levels were repressed. In an additional set of Rb tumor samples and pediatric healthy controls, we further validated differences in the expression of HK1 and E2F2. Through an integrated omics analysis of the transcriptomics and metabolomics of Rb, we uncovered a significantly altered tumor-specific metabolic circuit that reduces its dependence on glycolytic pathways and is governed by Rb1 and HK1.
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4
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Pearson JD, Huang K, Pacal M, McCurdy SR, Lu S, Aubry A, Yu T, Wadosky KM, Zhang L, Wang T, Gregorieff A, Ahmad M, Dimaras H, Langille E, Cole SPC, Monnier PP, Lok BH, Tsao MS, Akeno N, Schramek D, Wikenheiser-Brokamp KA, Knudsen ES, Witkiewicz AK, Wrana JL, Goodrich DW, Bremner R. Binary pan-cancer classes with distinct vulnerabilities defined by pro- or anti-cancer YAP/TEAD activity. Cancer Cell 2021; 39:1115-1134.e12. [PMID: 34270926 PMCID: PMC8981970 DOI: 10.1016/j.ccell.2021.06.016] [Citation(s) in RCA: 81] [Impact Index Per Article: 27.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/10/2020] [Revised: 09/17/2020] [Accepted: 06/24/2021] [Indexed: 12/13/2022]
Abstract
Cancer heterogeneity impacts therapeutic response, driving efforts to discover over-arching rules that supersede variability. Here, we define pan-cancer binary classes based on distinct expression of YAP and YAP-responsive adhesion regulators. Combining informatics with in vivo and in vitro gain- and loss-of-function studies across multiple murine and human tumor types, we show that opposite pro- or anti-cancer YAP activity functionally defines binary YAPon or YAPoff cancer classes that express or silence YAP, respectively. YAPoff solid cancers are neural/neuroendocrine and frequently RB1-/-, such as retinoblastoma, small cell lung cancer, and neuroendocrine prostate cancer. YAP silencing is intrinsic to the cell of origin, or acquired with lineage switching and drug resistance. The binary cancer groups exhibit distinct YAP-dependent adhesive behavior and pharmaceutical vulnerabilities, underscoring clinical relevance. Mechanistically, distinct YAP/TEAD enhancers in YAPoff or YAPon cancers deploy anti-cancer integrin or pro-cancer proliferative programs, respectively. YAP is thus pivotal across cancer, but in opposite ways, with therapeutic implications.
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Affiliation(s)
- Joel D Pearson
- Lunenfeld Tanenbaum Research Institute, Mt Sinai Hospital, Sinai Health System, Toronto, ON M5G 1X5, Canada; Department of Ophthalmology and Vision Science, University of Toronto, Toronto, ON M5T 3A9, Canada; Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Katherine Huang
- Lunenfeld Tanenbaum Research Institute, Mt Sinai Hospital, Sinai Health System, Toronto, ON M5G 1X5, Canada
| | - Marek Pacal
- Lunenfeld Tanenbaum Research Institute, Mt Sinai Hospital, Sinai Health System, Toronto, ON M5G 1X5, Canada
| | - Sean R McCurdy
- Lunenfeld Tanenbaum Research Institute, Mt Sinai Hospital, Sinai Health System, Toronto, ON M5G 1X5, Canada
| | - Suying Lu
- Lunenfeld Tanenbaum Research Institute, Mt Sinai Hospital, Sinai Health System, Toronto, ON M5G 1X5, Canada
| | - Arthur Aubry
- Lunenfeld Tanenbaum Research Institute, Mt Sinai Hospital, Sinai Health System, Toronto, ON M5G 1X5, Canada; Department of Ophthalmology and Vision Science, University of Toronto, Toronto, ON M5T 3A9, Canada; Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Tao Yu
- Lunenfeld Tanenbaum Research Institute, Mt Sinai Hospital, Sinai Health System, Toronto, ON M5G 1X5, Canada
| | - Kristine M Wadosky
- Department of Pharmacology & Therapeutics, Roswell Park Comprehensive Cancer Center, Buffalo, NY 14263, USA
| | - Letian Zhang
- Department of Pharmacology & Therapeutics, Roswell Park Comprehensive Cancer Center, Buffalo, NY 14263, USA
| | - Tao Wang
- Department of Pathology and Molecular Medicine, Queen's University, Kingston, ON K7L 3N6, Canada
| | - Alex Gregorieff
- Department of Pathology, McGill University and Cancer Research Program, Research Institute of the McGill University Health Centre, Montreal, ON H4A 3J1, Canada
| | - Mohammad Ahmad
- Lunenfeld Tanenbaum Research Institute, Mt Sinai Hospital, Sinai Health System, Toronto, ON M5G 1X5, Canada
| | - Helen Dimaras
- Department of Ophthalmology and Vision Science, University of Toronto, Toronto, ON M5T 3A9, Canada; The Department of Ophthalmology & Vision Sciences, Child Health Evaluative Sciences Program, and Center for Global Child Health, The Hospital for Sick Children, Toronto, ON M5G 1X8, Canada; Institute of Medical Science, University of Toronto, Toronto, ON M5S 1A8, Canada; Division of Clinical Public Health, Dalla Lana School of Public Health, The University of Toronto, Toronto, ON M5T 3M7, Canada
| | - Ellen Langille
- Lunenfeld Tanenbaum Research Institute, Mt Sinai Hospital, Sinai Health System, Toronto, ON M5G 1X5, Canada; Department of Molecular Genetics, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Susan P C Cole
- Division of Cancer Biology and Genetics, Queen's University Cancer Research Institute, Kingston, ON K7L 3N6, Canada
| | - Philippe P Monnier
- Department of Ophthalmology and Vision Science, University of Toronto, Toronto, ON M5T 3A9, Canada; Krembil Research Institute, Vision Division, Krembil Discovery Tower, Toronto, ON M5T 2S8, Canada; Department of Physiology, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Benjamin H Lok
- Institute of Medical Science, University of Toronto, Toronto, ON M5S 1A8, Canada; Princess Margaret Cancer Centre, University Health Network, Toronto, ON M5G 2M9, Canada; Department of Radiation Oncology, University of Toronto, Toronto, ON M5T 1P5, Canada; Department of Medical Biophysics, University of Toronto, Toronto, ON M5G 1L7, Canada
| | - Ming-Sound Tsao
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON M5S 1A8, Canada; Princess Margaret Cancer Centre, University Health Network, Toronto, ON M5G 2M9, Canada; Department of Medical Biophysics, University of Toronto, Toronto, ON M5G 1L7, Canada
| | - Nagako Akeno
- Division of Pathology & Laboratory Medicine, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, USA
| | - Daniel Schramek
- Lunenfeld Tanenbaum Research Institute, Mt Sinai Hospital, Sinai Health System, Toronto, ON M5G 1X5, Canada; Department of Molecular Genetics, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Kathryn A Wikenheiser-Brokamp
- Division of Pathology & Laboratory Medicine, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, USA; The Perinatal Institute Division of Pulmonary Biology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, USA; Department of Pathology & Laboratory Medicine, University of Cincinnati College of Medicine, Cincinnati, OH 45267, USA
| | - Erik S Knudsen
- Department of Molecular and Cellular Biology, Roswell Park Comprehensive Cancer Center, Buffalo, NY 14263, USA
| | - Agnieszka K Witkiewicz
- Department of Cancer Genetics and Genomics, Roswell Park Comprehensive Cancer Center, Buffalo, NY 14263, USA
| | - Jeffrey L Wrana
- Lunenfeld Tanenbaum Research Institute, Mt Sinai Hospital, Sinai Health System, Toronto, ON M5G 1X5, Canada; Department of Molecular Genetics, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - David W Goodrich
- Department of Pharmacology & Therapeutics, Roswell Park Comprehensive Cancer Center, Buffalo, NY 14263, USA
| | - Rod Bremner
- Lunenfeld Tanenbaum Research Institute, Mt Sinai Hospital, Sinai Health System, Toronto, ON M5G 1X5, Canada; Department of Ophthalmology and Vision Science, University of Toronto, Toronto, ON M5T 3A9, Canada; Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON M5S 1A8, Canada; Institute of Medical Science, University of Toronto, Toronto, ON M5S 1A8, Canada.
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5
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Wen N, Guo B, Zheng H, Xu L, Liang H, Wang Q, Wang D, Chen X, Zhang S, Li Y, Zhang L. Bromodomain inhibitor jq1 induces cell cycle arrest and apoptosis of glioma stem cells through the VEGF/PI3K/AKT signaling pathway. Int J Oncol 2019; 55:879-895. [PMID: 31485609 PMCID: PMC6741838 DOI: 10.3892/ijo.2019.4863] [Citation(s) in RCA: 43] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2019] [Accepted: 08/13/2019] [Indexed: 12/12/2022] Open
Abstract
Bromodomain and extraterminal domain proteins, especially bromodomain-containing protein 4 (Brd4), have recently emerged as therapeutic targets for several cancers, although the role and mechanism of Brd4 in glioblastoma multiforme (GBM) are unclear. In this study, we aimed to explore the underlying mechanisms of the anti-tumor effects of Brd4 and the bromodomain inhibitor JQ1 on glioma stem cells (GSCs). In vitro, JQ1 and small interfering RNAs targeting Brd4 (siBrd4) inhibited the proliferation and self-renewal of GSCs. In vivo, JQ1 significantly inhibited the growth of xenograft GSCs tumors. The RNA-seq analysis revealed that the PI3K-AKT pathway played an important role in GBM. Vascular endothelial growth factor (VEGF) and VEGF receptor 2 phosphorylation was downregulated by exposure to JQ1 in GSCs, thereby reducing PI3K and AKT activity. In addition, treatment with JQ1 inhibited MMP expression, thereby inhibiting degradation of the extracellular matrix by MMP and angiogenesis in GBM tumors. Suppression of AKT phosphorylation inhibited the expression of the retinoblastoma/E2F1 complex, resulting in cell cycle arrest. In addition, treatment with siBrd4 or JQ1 induced apoptosis by activating AKT downstream target genes involved in apoptosis. In conclusion, these results suggest that Brd4 has great potential as a therapeutic target, and JQ1 has notable anti-tumor effects against GBM which may be mediated via the VEGF/PI3K/AKT signaling pathway.
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Affiliation(s)
- Naiyan Wen
- Department of Pathophysiology, College of Basic Medical Sciences, Jilin University, Changchun, Jilin 130021, P.R. China
| | - Baofeng Guo
- Department of Plastic Surgery, China‑Japan Union Hospital, Jilin University, Changchun, Jilin 130033, P.R. China
| | - Hongwu Zheng
- Department of Pathology and Laboratory Medicine, Weill Cornell Medicine, New York, NY 10065, USA
| | - Libo Xu
- Department of Pathophysiology, College of Basic Medical Sciences, Jilin University, Changchun, Jilin 130021, P.R. China
| | - Hang Liang
- Department of Pathophysiology, College of Basic Medical Sciences, Jilin University, Changchun, Jilin 130021, P.R. China
| | - Qian Wang
- Department of Pathophysiology, College of Basic Medical Sciences, Jilin University, Changchun, Jilin 130021, P.R. China
| | - Ding Wang
- Department of Pathophysiology, College of Basic Medical Sciences, Jilin University, Changchun, Jilin 130021, P.R. China
| | - Xuyang Chen
- Department of Pathophysiology, College of Basic Medical Sciences, Jilin University, Changchun, Jilin 130021, P.R. China
| | - Shengnan Zhang
- Department of Pathophysiology, College of Basic Medical Sciences, Jilin University, Changchun, Jilin 130021, P.R. China
| | - Yang Li
- Department of Pathophysiology, College of Basic Medical Sciences, Jilin University, Changchun, Jilin 130021, P.R. China
| | - Ling Zhang
- Department of Pathophysiology, College of Basic Medical Sciences, Jilin University, Changchun, Jilin 130021, P.R. China
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6
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Goodrich MM, Talhouk R, Zhang X, Goodrich DW. An approach for controlling the timing and order of engineered mutations in mice. Genesis 2018; 56:e23243. [PMID: 30113769 DOI: 10.1002/dvg.23243] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2018] [Revised: 07/24/2018] [Accepted: 07/25/2018] [Indexed: 11/09/2022]
Abstract
Significant advances in our understanding of normal development and disease have been facilitated by engineered mice in which genes can be altered in a spatially, temporally, or cell type restricted manner using site specific recombinase systems like Cre-loxP or Flp-frt. In many circumstances it is important to understand how interactions between multiple genes influence a given phenotype. Robust approaches for precisely controlling multiple genetic alterations independently are limited, however, thus the impact of mutation order and timing on phenotype is generally unknown. Here we describe and validate a novel Gt(ROSA)26Sor targeted transgene allowing precise control over the order and timing of multiple genetic mutations in the mouse. The transgene expresses an optimized, Flp-estrogen receptor fusion protein (Flpo-ERT2) under the control of a loxP-stop-loxP cassette. In this system, genes modified by loxP sites are altered first upon expression of Cre. Cre also eliminates the loxP-stop-loxP cassette, permitting widespread expression of Flpo-ERT2. Because of the estrogen receptor fusion, Flp activity remains inert until administration of tamoxifen, allowing genes modified by frt sites to be modified subsequently with controllable timing. This mouse transgene will be useful in a wide variety of applications where independent control of different mutations in the mouse is desirable.
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Affiliation(s)
- Maxwell M Goodrich
- Department of Pharmacology & Therapeutics, Roswell Park Cancer Institute, Buffalo, New York
| | - Ramzi Talhouk
- Department of Pharmacology & Therapeutics, Roswell Park Cancer Institute, Buffalo, New York
| | - Xiaojing Zhang
- Department of Pharmacology & Therapeutics, Roswell Park Cancer Institute, Buffalo, New York
| | - David W Goodrich
- Department of Pharmacology & Therapeutics, Roswell Park Cancer Institute, Buffalo, New York
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7
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Thwaites MJ, Cecchini MJ, Talluri S, Passos DT, Carnevale J, Dick FA. Multiple molecular interactions redundantly contribute to RB-mediated cell cycle control. Cell Div 2017; 12:3. [PMID: 28293272 PMCID: PMC5348811 DOI: 10.1186/s13008-017-0029-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2016] [Accepted: 02/28/2017] [Indexed: 02/07/2023] Open
Abstract
Background The G1-S phase transition is critical to maintaining proliferative control and preventing carcinogenesis. The retinoblastoma tumor suppressor is a key regulator of this step in the cell cycle. Results Here we use a structure–function approach to evaluate the contributions of multiple protein interaction surfaces on pRB towards cell cycle regulation. SAOS2 cell cycle arrest assays showed that disruption of three separate binding surfaces were necessary to inhibit pRB-mediated cell cycle control. Surprisingly, mutation of some interaction surfaces had no effect on their own. Rather, they only contributed to cell cycle arrest in the absence of other pRB dependent arrest functions. Specifically, our data shows that pRB–E2F interactions are competitive with pRB–CDH1 interactions, implying that interchangeable growth arrest functions underlie pRB’s ability to block proliferation. Additionally, disruption of similar cell cycle control mechanisms in genetically modified mutant mice results in ectopic DNA synthesis in the liver. Conclusions Our work demonstrates that pRB utilizes a network of mechanisms to prevent cell cycle entry. This has important implications for the use of new CDK4/6 inhibitors that aim to activate this proliferative control network.
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Affiliation(s)
- Michael J Thwaites
- London Regional Cancer Program, London, Canada.,Department of Biochemistry, Western University, London, ON Canada
| | - Matthew J Cecchini
- London Regional Cancer Program, London, Canada.,Department of Biochemistry, Western University, London, ON Canada
| | - Srikanth Talluri
- London Regional Cancer Program, London, Canada.,Department of Biochemistry, Western University, London, ON Canada
| | - Daniel T Passos
- London Regional Cancer Program, London, Canada.,Department of Biochemistry, Western University, London, ON Canada
| | - Jasmyne Carnevale
- London Regional Cancer Program, London, Canada.,Department of Biochemistry, Western University, London, ON Canada
| | - Frederick A Dick
- London Regional Cancer Program, London, Canada.,Children's Health Research Institute, London, Canada.,Department of Biochemistry, Western University, London, ON Canada
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8
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Aldiri I, Ajioka I, Xu B, Zhang J, Chen X, Benavente C, Finkelstein D, Johnson D, Akiyama J, Pennacchio LA, Dyer MA. Brg1 coordinates multiple processes during retinogenesis and is a tumor suppressor in retinoblastoma. Development 2016; 142:4092-106. [PMID: 26628093 PMCID: PMC4712833 DOI: 10.1242/dev.124800] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Retinal development requires precise temporal and spatial coordination of cell cycle exit, cell fate specification, cell migration and differentiation. When this process is disrupted, retinoblastoma, a developmental tumor of the retina, can form. Epigenetic modulators are central to precisely coordinating developmental events, and many epigenetic processes have been implicated in cancer. Studying epigenetic mechanisms in development is challenging because they often regulate multiple cellular processes; therefore, elucidating the primary molecular mechanisms involved can be difficult. Here we explore the role of Brg1 (Smarca4) in retinal development and retinoblastoma in mice using molecular and cellular approaches. Brg1 was found to regulate retinal size by controlling cell cycle length, cell cycle exit and cell survival during development. Brg1 was not required for cell fate specification but was required for photoreceptor differentiation and cell adhesion/polarity programs that contribute to proper retinal lamination during development. The combination of defective cell differentiation and lamination led to retinal degeneration in Brg1-deficient retinae. Despite the hypocellularity, premature cell cycle exit, increased cell death and extended cell cycle length, retinal progenitor cells persisted in Brg1-deficient retinae, making them more susceptible to retinoblastoma. ChIP-Seq analysis suggests that Brg1 might regulate gene expression through multiple mechanisms. Summary: The SWI/SNF protein Brg1 controls cell cycle length, cell cycle exit and cell survival, and is required for cell differentiation and retinal lamination, in the developing mouse retina.
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Affiliation(s)
- Issam Aldiri
- Department of Developmental Neurobiology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Itsuki Ajioka
- Center for Brain Integration Research (CBIR), Tokyo Medical and Dental University (TMDU), Tokyo 113-8510, Japan
| | - Beisi Xu
- Department of Computational Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Jiakun Zhang
- Department of Developmental Neurobiology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Xiang Chen
- Department of Computational Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Claudia Benavente
- Department of Developmental Neurobiology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - David Finkelstein
- Department of Computational Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Dianna Johnson
- Department of Ophthalmology, University of Tennessee Health Science Center, Memphis, TN 38163, USA
| | - Jennifer Akiyama
- Lawrence Berkeley National Laboratory, Genomics Division, Berkeley, CA 94701, USA Department of Energy, Joint Genome Institute, Walnut Creek, CA 94598, USA
| | - Len A Pennacchio
- Lawrence Berkeley National Laboratory, Genomics Division, Berkeley, CA 94701, USA Department of Energy, Joint Genome Institute, Walnut Creek, CA 94598, USA
| | - Michael A Dyer
- Department of Developmental Neurobiology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA Department of Ophthalmology, University of Tennessee Health Science Center, Memphis, TN 38163, USA Howard Hughes Medical Institute, Chevy Chase, MD 20815, USA
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9
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Evaluating Effects of Hypomorphic Thoc1 Alleles on Embryonic Development in Rb1 Null Mice. Mol Cell Biol 2016; 36:1621-7. [PMID: 27001308 DOI: 10.1128/mcb.01003-15] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2015] [Accepted: 03/16/2016] [Indexed: 12/22/2022] Open
Abstract
The Rb1 tumor suppressor protein is a molecular adaptor that physically links transcription factors like E2f with various proteins acting on DNA or RNA to repress gene expression. Loss of Rb1 liberates E2f to activate the expression of genes mediating resulting phenotypes. Most Rb1 binding proteins, including E2f, interact through carboxyl-terminal protein interaction domains, but genetic evidence suggests that an amino-terminal protein interaction domain is also important. One protein that binds Rb1 through the amino-terminal domain is encoded by Thoc1, a required component of the THO ribonucleoprotein complex important for RNA processing and transport. The physiological relevance of this interaction is unknown. Here we tested whether Thoc1 mediates effects of Rb1 loss on mouse embryonic development. We found that Thoc1 deficiency delays embryo death, and this delay correlates with reduced apoptosis in the brain. E2f protein levels are reduced in Rb1:Thoc1-deficient brain tissue. Expression of apoptotic regulatory genes regulated by E2f, like Apaf1 and Bak1, is also reduced. These observations suggest that Thoc1 is required to support increased expression of E2f and apoptotic regulatory genes that trigger apoptosis upon Rb1 loss. These findings implicate Rb1 in the regulation of the THO ribonucleoprotein complex.
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10
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Tarang S, Doi SMSR, Gurumurthy CB, Harms D, Quadros R, Rocha-Sanchez SM. Generation of a Retinoblastoma (Rb)1-inducible dominant-negative (DN) mouse model. Front Cell Neurosci 2015; 9:52. [PMID: 25755634 PMCID: PMC4337335 DOI: 10.3389/fncel.2015.00052] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2014] [Accepted: 02/03/2015] [Indexed: 11/13/2022] Open
Abstract
Retinoblastoma 1 (Rb1) is an essential gene regulating cellular proliferation, differentiation, and homeostasis. To exert these functions, Rb1 is recruited and physically interacts with a growing variety of signaling pathways. While Rb1 does not appear to be ubiquitously expressed, its expression has been confirmed in a variety of hematopoietic and neuronal-derived cells, including the inner ear hair cells (HCs). Studies in transgenic mice demonstrate that complete germline or conditional Rb1 deletion leads to abnormal cell proliferation, followed by massive apoptosis; making it difficult to fully address Rb1's biochemical activities. To overcome these limitations, we developed a tetracycline-inducible TetO-CB-myc6-Rb1 (CBRb) mouse model to achieve transient and inducible dominant-negative (DN) inhibition of the endogenous RB1 protein. Our strategy involved fusing the Rb1 gene to the lysosomal protease pre-procathepsin B (CB), thus allowing for further routing of the DN-CBRb fusion protein and its interacting complexes for proteolytic degradation. Moreover, reversibility of the system is achieved upon suppression of doxycycline (Dox) administration. Preliminary characterization of DN-CBRb mice bred to a ubiquitous rtTA mouse line demonstrated a significant inhibition of the endogenous RB1 protein in the inner ear and in a number of other organs where RB1 is expressed. Examination of the postnatal (P) DN-CBRb mice inner ear at P10 and P28 showed the presence of supernumerary inner HCs (IHCs) in the lower turns of the cochleae, which corresponds to the described expression domain of the endogenous Rb1 gene. Selective and reversible suppression of gene expression is both an experimental tool for defining function and a potential means to medical therapy. Given the limitations associated with Rb1-null mice lethality, this model provides a valuable resource for understanding RB1 activity, relative contribution to HC regeneration and its potential therapeutic application.
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Affiliation(s)
- Shikha Tarang
- Department of Oral Biology, Creighton University School of Dentistry Omaha, NE,USA
| | - Songila M S R Doi
- Department of Oral Biology, Creighton University School of Dentistry Omaha, NE,USA
| | - Channabasavaiah B Gurumurthy
- Mouse Genome Engineering Core Facility, Department of Genetics Cell Biology and Anatomy, University of Nebraska Medical Center Omaha, NE, USA
| | - Donald Harms
- Mouse Genome Engineering Core Facility, Department of Genetics Cell Biology and Anatomy, University of Nebraska Medical Center Omaha, NE, USA
| | - Rolen Quadros
- Mouse Genome Engineering Core Facility, Department of Genetics Cell Biology and Anatomy, University of Nebraska Medical Center Omaha, NE, USA
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11
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Popov B, Petrov N. pRb-E2F signaling in life of mesenchymal stem cells: Cell cycle, cell fate, and cell differentiation. Genes Dis 2014; 1:174-187. [PMID: 30258863 PMCID: PMC6150080 DOI: 10.1016/j.gendis.2014.09.007] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2014] [Accepted: 09/14/2014] [Indexed: 02/07/2023] Open
Abstract
Mesenchymal stem cells (MSCs) are multipotent cells that can differentiate into various mesodermal lines forming fat, muscle, bone, and other lineages of connective tissue. MSCs possess plasticity and under special metabolic conditions may transform into cells of unusual phenotypes originating from ecto- and endoderm. After transplantation, MSCs release the humoral factors promoting regeneration of the damaged tissue. During last five years, the numbers of registered clinical trials of MSCs have increased about 10 folds. This gives evidence that MSCs present a new promising resource for cell therapy of the most dangerous diseases. The efficacy of the MSCs therapy is limited by low possibilities to regulate their conversion into cells of damaged tissues that is implemented by the pRb-E2F signaling. The widely accepted viewpoint addresses pRb as ubiquitous regulator of cell cycle and tumor suppressor. However, current publications suggest that basic function of the pRb-E2F signaling in development is to regulate cell fate and differentiation. Through facultative and constitutive chromatin modifications, pRb-E2F signaling promotes transient and stable cells quiescence, cell fate choice to differentiate, to senesce, or to die. Loss of pRb is associated with cancer cell fate. pRb regulates cell fate by retaining quiescence of one cell population in favor of commitment of another or by suppression of genes of different cell phenotype. pRb is the founder member of the "pocket protein" family possessing functional redundancy. Critical increase in the efficacy of the MSCs based cell therapy will depend on precise understanding of various aspects of the pRb-E2F signaling.
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Affiliation(s)
- Boris Popov
- Institute of Cytology, Russian Academy of Sciences, St.Petersburg, 4, Tikhoretsky Av., 194064, Russia
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12
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Toki H, Inoue M, Minowa O, Motegi H, Saiki Y, Wakana S, Masuya H, Gondo Y, Shiroishi T, Yao R, Noda T. Novel retinoblastoma mutation abrogating the interaction to E2F2/3, but not E2F1, led to selective suppression of thyroid tumors. Cancer Sci 2014; 105:1360-8. [PMID: 25088905 PMCID: PMC4462357 DOI: 10.1111/cas.12495] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2014] [Revised: 07/18/2014] [Accepted: 07/25/2014] [Indexed: 01/18/2023] Open
Abstract
Mutant mouse models are indispensable tools for clarifying gene functions and elucidating the pathogenic mechanisms of human diseases. Here, we describe novel cancer models bearing point mutations in the retinoblastoma gene (Rb1) generated by N-ethyl-N-nitrosourea mutagenesis. Two mutations in splice sites reduced Rb1 expression and led to a tumor spectrum and incidence similar to those observed in the conventional Rb1 knockout mice. The missense mutant, Rb1D326V/+, developed pituitary tumors, but thyroid tumors were completely suppressed. Immunohistochemical analyses of thyroid tissue revealed that E2F1, but not E2F2/3, was selectively inactivated, indicating that the mutant Rb protein (pRb) suppressed thyroid tumors by inactivating E2F1. Interestingly, Rb1D326V/+ mice developed pituitary tumors that originated from the intermediate lobe of the pituitary, despite selective inactivation of E2F1. Furthermore, in the anterior lobe of the pituitary, other E2F were also inactivated. These observations show that pRb mediates the inactivation of E2F function and its contribution to tumorigenesis is highly dependent on the cell type. Last, by using a reconstitution assay of synthesized proteins, we showed that the D326V missense pRb bound to E2F1 but failed to interact with E2F2/3. These results reveal the effect of the pRb N-terminal domain on E2F function and the impact of the protein on tumorigenesis. Thus, this mutant mouse model can be used to investigate human Rb family-bearing mutations at the N-terminal region.
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Affiliation(s)
- Hideaki Toki
- Team for Advanced Development and Evaluation of Human Disease Models, Riken BioResource Center, Tsukuba, Ibaraki, Japan
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13
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RBF binding to both canonical E2F targets and noncanonical targets depends on functional dE2F/dDP complexes. Mol Cell Biol 2012; 32:4375-87. [PMID: 22927638 DOI: 10.1128/mcb.00536-12] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The retinoblastoma (RB) family of proteins regulate transcription. These proteins lack intrinsic DNA-binding activity but are recruited to specific genomic locations through interactions with sequence-specific DNA-binding factors. The best-known target of RB protein (pRB) is the E2F transcription factor; however, many other chromatin-associated proteins have been described that may allow RB family members to act at additional sites. To gain a perspective on the scale of E2F-dependent and E2F-independent functions, we generated genome-wide binding profiles of RBF1 and dE2F proteins in Drosophila larvae. RBF1 and dE2F2 associate with a large number of binding sites at genes with diverse biological functions. In contrast, dE2F1 was detected at a smaller set of promoters, suggesting that it overrides repression by RBF1/dE2F2 at a specific subset of targets. Approximately 15% of RBF1-bound regions lacked consensus E2F-binding motifs. To test whether RBF1 action at these sites is E2F independent, we examined dDP mutant larvae that lack any functional dE2F/dDP heterodimers. As measured by chromatin immunoprecipitation-microarray analysis (ChIP-chip), ChIP-quantitative PCR (qPCR), and cell fractionation, the stable association of RBF1 with chromatin was eliminated in dDP mutants. This requirement for dDP was seen at classic E2F-regulated promoters and at promoters that lacked canonical E2F-binding sites. These results suggest that E2F/DP complexes are essential for all genomic targeting of RBF1.
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E2f binding-deficient Rb1 protein suppresses prostate tumor progression in vivo. Proc Natl Acad Sci U S A 2010; 108:704-9. [PMID: 21187395 DOI: 10.1073/pnas.1015027108] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Mutational inactivation of the RB1 tumor suppressor gene initiates retinoblastoma and other human cancers. RB1 protein (pRb) restrains cell proliferation by binding E2f transcription factors and repressing the expression of cell cycle target genes. It is presumed that loss of pRb/E2f interaction accounts for tumor initiation, but this has not been directly tested. RB1 mutation is a late event in other human cancers, suggesting a role in tumor progression as well as initiation. It is currently unknown whether RB1 mutation drives tumor progression and, if so, whether loss of pRb/E2f interaction is responsible. We have characterized tumorigenesis in mice expressing a mutant pRb that is specifically deficient in binding E2f. In endocrine tissue, the mutant pRb has no detectable effect on tumorigenesis. In contrast, it significantly delays progression to invasive and lethal prostate cancer. Tumor delay is associated with induction of a senescence response. We conclude that the pRb/E2f interaction is critical for preventing tumor initiation, but that pRb can use additional context-dependent mechanisms to restrain tumor progression.
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Xiao H, Zhang X, Goodrich DW. Construction of a dual affinity tagged allele of the Rb1 tumor suppressor gene in the mouse. Genesis 2010; 48:121-6. [PMID: 20027616 DOI: 10.1002/dvg.20589] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Loss of Rb1 tumor suppressor gene function is involved in the genesis of most human cancers. Novel therapies targeting Rb1 have been slow to develop because of our incomplete understanding of its molecular mechanisms of action. Rb1 protein (pRb) binds a host of cellular genes and proteins, and these molecular interactions mediate its various functions. Given the potential complexity of these molecular interactions and the lack of established methods for pRb purification, it has been difficult to systematically identify gene and protein interactions relevant to tumor suppression in different tissues in vivo. To address this limitation, we have generated a dual affinity tagged Rb1 allele in the mouse. The tagged allele functions as wild type and the encoded protein can be purified by tandem affinity chromatography. This allele will facilitate identification and characterization of native pRb molecular interactions in any tissue accessible in the mouse.
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Affiliation(s)
- Hai Xiao
- Department of Pharmacology and Therapeutics, Roswell Park Cancer Institute, Buffalo, New York 14263, USA
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Popov BV, Watt SM, Rosanov JM, Chang LS. A structural pocket mutation of pRb increases its affinity for E2F4, which is coupled with activation of muscle differentiation. Mol Biol 2010. [DOI: 10.1134/s0026893310020147] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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17
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Samardzija M, Neuhauss SCF, Joly S, Kurz-Levin M, Grimm C. Animal Models for Retinal Degeneration. NEUROMETHODS 2010. [DOI: 10.1007/978-1-60761-541-5_4] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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18
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Detection of miR-106a in gastric carcinoma and its clinical significance. Clin Chim Acta 2009; 400:97-102. [DOI: 10.1016/j.cca.2008.10.021] [Citation(s) in RCA: 130] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2008] [Revised: 10/16/2008] [Accepted: 10/20/2008] [Indexed: 12/23/2022]
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Park Y, Kubo A, Komiya T, Coxon A, Beebe K, Neckers L, Meltzer PS, Kaye FJ. Low-penetrant RB allele in small-cell cancer shows geldanamycin instability and discordant expression with mutant ras. Cell Cycle 2008; 7:2384-91. [PMID: 18677112 DOI: 10.4161/cc.6363] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Certain kindreds with low-penetrant (lp) retinoblastoma carry mutant alleles which retain partial tumor suppressor activity and we previously showed that these alleles exhibit defective, temperature-sensitive binding in yeast. To investigate the molecular basis for incomplete penetrance, we studied three recurrent lp alleles and observed approximately 50% of wildtype activity measured by (i) phosphorylation at key regulatory sites, S780, S795, S807/S811, (ii) transcriptional co-activation, and (iii) 'flat-cell' differentiation in mammalian cells in vivo. In addition, we studied a small-cell carcinoma that is homozygous for the R661W allele providing the first analysis of the effect of a naturally occurring lp allele in a human tumor. While we detected abundant expression of the R661W protein, we noted marked instability of both endogenous and recombinant R661W following treatment in vivo with the Hsp90 inhibitor, geldanamycin and stabilization of R661W following heat shock. In addition, we observed a discordant phenotype in the tumor cells with induction of p16 and loss of cyclin D1 consistent with a null RB status combined with homozygous expression of mutant ras which had not been reported previously for RB (-) small-cell cancer. These findings show that a recurrent missense lp allele retains greater functional activity in vivo than predicted from earlier in vitro assays, proposing a role for stabilizing chaperone-like activity in vivo. In addition, these data suggest that reversible protein instability and the requirement for a cooperating mutation may provide a stochastic explanation for the molecular basis of incomplete penetrance in kindreds carrying these alleles.
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Affiliation(s)
- Yoonsoo Park
- Genetics Branch, Center for Cancer Research, National Cancer Institute and National Naval Medical Center, Bethesda, Maryland 20889, USA
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Abstract
It is widely accepted that adenoviral E1A exerts its influence on recipient cells through binding to the retinoblastoma (Rb) family proteins, followed by a global release of E2F factors from pocket-protein control. Our study challenges this simple paradigm by demonstrating previously unappreciated complexity. We show that E1A-expressing primary and transformed cells are characterized by the persistence of Rb-E2F1 complexes. We provide evidence that E1A causes Rb stabilization by interfering with its proteasomal degradation. Functional experiments supported by biochemical data reveal not only a dramatic increase in Rb and E2F1 protein levels in E1A-expressing cells but also demonstrate their activation throughout the cell cycle. We further show that E1A activates an Rb- and E2F1-dependent S-phase checkpoint that attenuates the growth of cells that became hyperploid through errors in mitosis and supports the fidelity DNA replication even in the absence of E2F complexes with other Rb family proteins, thereby functionally substituting for the loss of p53. Our results support the essential role of Rb and E2F1 in the regulation of genomic stability and DNA damage checkpoints.
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Deregulated E2f-2 underlies cell cycle and maturation defects in retinoblastoma null erythroblasts. Mol Cell Biol 2007; 27:8713-28. [PMID: 17923680 DOI: 10.1128/mcb.01118-07] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
By assessing the contribution of deregulated E2F activity to erythroid defects in Rb null mice, we have identified E2f-2 as being upregulated in end-stage red cells, where we show it is the major pRb-associated E2f and the predominant E2f detected at key target gene promoters. Consistent with its expression pattern, E2f-2 loss restored terminal erythroid maturation to Rb null red cells, including the ability to undergo enucleation. Deletion of E2f-2 also extended the life span of Rb null mice despite persistent defects in placental development, indicating that deregulated E2f-2 activity in differentiating erythroblasts contributes to the premature lethality of Rb null mice. We show that the aberrant entry of Rb null erythroblasts into S phase at times in differentiation when wild-type erythroblasts are exiting the cell cycle is inhibited by E2f-2 deletion. E2f-2 loss induced cell cycle arrest in both wild-type and Rb null erythroblasts and was associated with increased DNA double-strand breaks. These results implicate deregulated E2f-2 in the cell cycle defects observed in Rb null erythroblasts and reveal a novel role for E2f-2 during terminal red blood cell differentiation. The identification of a tissue-restricted role for E2f-2 in erythropoiesis highlights the nonredundant nature of E2f transcription factor activities in cell growth and differentiation.
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Abstract
Studies on retinoblastoma have been at the heart of many of the landmark discoveries in cancer genetics over the past 35 years. However, these advances in the laboratory have had little effect on the treatment of children with retinoblastoma. One of the reasons for this has been the lack of preclinical models that recapitulated the genetic and histopathologic features of human retinoblastoma. In the past three years, a series of new animal models of retinoblastoma has been developed and characterized from several different laboratories using a variety of experimental approaches. It is encouraging that there is broad agreement about the consequences of inactivation of the Rb family in retinal development from these studies. More importantly, these new mouse models of retinoblastoma have contributed to clinical trials and novel therapeutic approaches for treating this debilitating childhood cancer.
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Affiliation(s)
- David MacPherson
- Department of Embryology, Carnegie Institution, Baltimore, Maryland, USA.
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Dick FA. Structure-function analysis of the retinoblastoma tumor suppressor protein - is the whole a sum of its parts? Cell Div 2007; 2:26. [PMID: 17854503 PMCID: PMC2082274 DOI: 10.1186/1747-1028-2-26] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2007] [Accepted: 09/13/2007] [Indexed: 12/28/2022] Open
Abstract
Biochemical analysis of the retinoblastoma protein's function has received considerable attention since it was cloned just over 20 years ago. During this time pRB has emerged as a key regulator of the cell division cycle and its ability to block proliferation is disrupted in the vast majority of human cancers. Much has been learned about the regulation of E2F transcription factors by pRB in the cell cycle. However, many questions remain unresolved and researchers continue to explore this multifunctional protein. In particular, understanding how its biochemical functions contribute to its role as a tumor suppressor remains to be determined. Since pRB has been shown to function as an adaptor molecule that links different proteins together, or to particular promoters, analyzing pRB by disrupting individual protein interactions holds tremendous promise in unraveling the intricacies of its function. Recently, crystal structures have reported how pRB interacts with some of its molecular partners. This information has created the possibility of rationally separating pRB functions by studying mutants that disrupt individual binding sites. This review will focus on literature that investigates pRB by isolating functions based on binding sites within the pocket domain. This article will also discuss the prospects for using this approach to further explore the unknown functions of pRB.
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Benevolenskaya EV. Histone H3K4 demethylases are essential in development and differentiationThis paper is one of a selection of papers published in this Special Issue, entitled 28th International West Coast Chromatin and Chromosome Conference, and has undergone the Journal's usual peer review process. Biochem Cell Biol 2007; 85:435-43. [PMID: 17713579 DOI: 10.1139/o07-057] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Lysine histone methylation is one of the most robust epigenetic marks and is essential for the regulation of multiple cellular processes. The methylation of Lys4 of histone H3 seems to be of particular significance. It is associated with active regions of the genome, and in Drosophila it is catalyzed by trithorax-group proteins that have become paradigms of developmental regulators at the level of chromatin. Like other histone methylation events, H3K4 methylation was considered irreversible until the identification of a large number of histone demethylases indicated that demethylation events play an important role in histone modification dynamics. However, the described demethylases had no strictly assigned biological functions and the identity of the histone demethylases that would contribute to the epigenetic changes specifying certain biological processes was unknown. Recently, several groups presented evidence that a family of 4 JmjC domain proteins results in the global changes of histone demethylation, and in elegant studies using model organisms, they demonstrated the importance of this family of histone demethylases in cell fate determination. All 4 proteins possess the demethylase activity specific to H3K4 and belong to the poorly described JARID1 protein family.
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Affiliation(s)
- Elizaveta V Benevolenskaya
- Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, 900 S. Ashland Avenue, Chicago, IL 60607, USA.
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Abstract
The retinoblastoma tumor-suppressor gene (Rb1) is centrally important in cancer research. Mutational inactivation of Rb1 causes the pediatric cancer retinoblastoma, while deregulation of the pathway in which it functions is common in most types of human cancer. The Rb1-encoded protein (pRb) is well known as a general cell cycle regulator, and this activity is critical for pRb-mediated tumor suppression. The main focus of this review, however, is on more recent evidence demonstrating the existence of additional, cell type-specific pRb functions in cellular differentiation and survival. These additional functions are relevant to carcinogenesis suggesting that the net effect of Rb1 loss on the behavior of resulting tumors is highly dependent on biological context. The molecular mechanisms underlying pRb functions are based on the cellular proteins it interacts with and the functional consequences of those interactions. Better insight into pRb-mediated tumor suppression and clinical exploitation of pRb as a therapeutic target will require a global view of the complex, interdependent network of pocket protein complexes that function simultaneously within given tissues.
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Affiliation(s)
- D W Goodrich
- Department of Pharmacology & Therapeutics, Roswell Park Cancer Institute, Buffalo, NY 14263, USA.
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Donovan SL, Schweers B, Martins R, Johnson D, Dyer MA. Compensation by tumor suppressor genes during retinal development in mice and humans. BMC Biol 2006; 4:14. [PMID: 16672052 PMCID: PMC1481602 DOI: 10.1186/1741-7007-4-14] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2006] [Accepted: 05/03/2006] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The RB1 gene was the first tumor suppressor gene cloned from humans by studying genetic lesions in families with retinoblastoma. Children who inherit one defective copy of the RB1 gene have an increased susceptibility to retinoblastoma. Several years after the identification of the human RB1 gene, a targeted deletion of Rb was generated in mice. Mice with one defective copy of the Rb gene do not develop retinoblastoma. In this manuscript, we explore the different roles of the Rb family in human and mouse retinal development in order to better understand the species-specific difference in retinoblastoma susceptibility. RESULTS We found that the Rb family of proteins (Rb, p107 and p130) are expressed in a dynamic manner during mouse retinal development. The primary Rb family member expressed in proliferating embryonic retinal progenitor cells in mice is p107, which is required for appropriate cell cycle exit during retinogenesis. The primary Rb family member expressed in proliferating postnatal retinal progenitor cells is Rb. p130 protein is expressed redundantly with Rb in postmitotic cells of the inner nuclear layer and the ganglion cell layer of the mouse retina. When Rb is inactivated in an acute or chronic manner during mouse retinal development, p107 is upregulated in a compensatory manner. Similarly, when p107 is inactivated in the mouse retina, Rb is upregulated. No changes in p130 expression were seen when p107, Rb or both were inactivated in the developing mouse retina. In the human retina, RB1 was the primary family member expressed throughout development. There was very little if any p107 expressed in the developing human retina. In contrast to the developing mouse retina, when RB1 was acutely inactivated in the developing human fetal retina, p107 was not upregulated in a compensatory manner. CONCLUSION We propose that intrinsic genetic compensation between Rb and p107 prevents retinoblastoma in Rb- or p107-deficient mice, but this compensation does not occur in humans. Together, these data suggest a model that explains why humans are susceptible to retinoblastoma following RB1 loss, but mice require both Rb and p107 gene inactivation.
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Affiliation(s)
- Stacy L Donovan
- Department of Developmental Neurobiology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Brett Schweers
- Department of Developmental Neurobiology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Rodrigo Martins
- Department of Developmental Neurobiology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Dianna Johnson
- Department of Ophthalmology, University of Tennessee Health Science Center, Memphis, TN 38163, USA
| | - Michael A Dyer
- Department of Developmental Neurobiology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
- Department of Ophthalmology, University of Tennessee Health Science Center, Memphis, TN 38163, USA
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