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Telomere Transcription in MLL-Rearranged Leukemia Cell Lines: Increased Levels of TERRA Associate with Lymphoid Lineage and Are Independent of Telomere Length and Ploidy. Biomedicines 2023; 11:biomedicines11030925. [PMID: 36979904 PMCID: PMC10046226 DOI: 10.3390/biomedicines11030925] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2023] [Revised: 02/25/2023] [Accepted: 03/02/2023] [Indexed: 03/19/2023] Open
Abstract
Telomere transcription into telomeric repeat-containing RNA (TERRA) is an integral component of all aspects of chromosome end protection consisting of telomerase- or recombination-dependent telomere elongation, telomere capping, and the preservation of the (sub)telomeric heterochromatin structure. The chromatin modifier and transcriptional regulator MLL binds to telomeres and regulates TERRA transcription in telomere length homeostasis and response to telomere dysfunction. MLL fusion proteins (MLL-FPs), the product of MLL rearrangements in leukemia, also bind to telomeric chromatin. However, an effect on telomere transcription in MLL-rearranged (MLL-r) leukemia has not yet been evaluated. Here, we show increased UUAGGG repeat-containing RNA levels in MLL-r acute lymphoblastic leukemia (ALL) when compared to non-MLL-r ALL and myeloid leukemia. MLL rearrangements do not affect telomere length and UUAGGG repeat-containing RNA levels correlate with mean telomere length and reflect increased levels of TERRA. Furthermore, high levels of TERRA in MLL-r ALL occur in the presence of telomerase activity and are independent of ploidy, an underestimated source of variation on the overall transcriptome size in a cell. This MLL rearrangement-dependent and lymphoid lineage-associated increase in levels of TERRA supports a sustained telomere transcription by MLL-FPs that correlates with marked genomic stability previously reported in pediatric MLL-r ALL.
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The Trithorax group protein ASH1 requires a combination of BAH domain and AT hooks, but not the SET domain, for mitotic chromatin binding and survival. Chromosoma 2021; 130:215-234. [PMID: 34331109 PMCID: PMC8426247 DOI: 10.1007/s00412-021-00762-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2020] [Revised: 07/03/2021] [Accepted: 07/06/2021] [Indexed: 11/20/2022]
Abstract
The Drosophila Trithorax group (TrxG) protein ASH1 remains associated with mitotic chromatin through mechanisms that are poorly understood. ASH1 dimethylates histone H3 at lysine 36 via its SET domain. Here, we identify domains of the TrxG protein ASH1 that are required for mitotic chromatin attachment in living Drosophila. Quantitative live imaging demonstrates that ASH1 requires AT hooks and the BAH domain but not the SET domain for full chromatin binding in metaphase, and that none of these domains are essential for interphase binding. Genetic experiments show that disruptions of the AT hooks and the BAH domain together, but not deletion of the SET domain alone, are lethal. Transcriptional profiling demonstrates that intact ASH1 AT hooks and the BAH domain are required to maintain expression levels of a specific set of genes, including several involved in cell identity and survival. This study identifies in vivo roles for specific ASH1 domains in mitotic binding, gene regulation, and survival that are distinct from its functions as a histone methyltransferase.
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Parameswaran S, Vizeacoumar FS, Kalyanasundaram Bhanumathy K, Qin F, Islam MF, Toosi BM, Cunningham CE, Mousseau DD, Uppalapati MC, Stirling PC, Wu Y, Bonham K, Freywald A, Li H, Vizeacoumar FJ. Molecular characterization of an MLL1 fusion and its role in chromosomal instability. Mol Oncol 2018; 13:422-440. [PMID: 30548174 PMCID: PMC6360371 DOI: 10.1002/1878-0261.12423] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2018] [Revised: 11/06/2018] [Accepted: 11/26/2018] [Indexed: 01/02/2023] Open
Abstract
Chromosomal rearrangements involving the mixed‐lineage leukemia (MLL1) gene are common in a unique group of acute leukemias, with more than 100 fusion partners in this malignancy alone. However, do these fusions occur or have a role in solid tumors? We performed extensive network analyses of MLL1‐fusion partners in patient datasets, revealing that multiple MLL1‐fusion partners exhibited significant interactions with the androgen‐receptor signaling pathway. Further exploration of tumor sequence data from TCGA predicts the presence of MLL1 fusions with truncated SET domain in prostate tumors. To investigate the physiological relevance of MLL1 fusions in solid tumors, we engineered a truncated version of MLL1 by fusing it with one of its known fusion partners, ZC3H13, to use as a model system. Functional characterization with cell‐based assays revealed that MLL1‐ZC3H13 fusion induced chromosomal instability, affected mitotic progression, and enhanced tumorsphere formation. The MLL1‐ZC3H13 chimera consistently increased the expression of a cancer stem cell marker (CD44); in addition, we detected potential collateral lethality between DOT1L and MLL1 fusions. Our work reveals that MLL1 fusions are likely prevalent in solid tumors and exhibit a potential pro‐tumorigenic role.
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Affiliation(s)
- Sreejit Parameswaran
- Department of Pathology and Laboratory Medicine, Cancer Cluster, College of Medicine, University of Saskatchewan, Saskatoon, Canada
| | - Frederick S Vizeacoumar
- Department of Pathology and Laboratory Medicine, Cancer Cluster, College of Medicine, University of Saskatchewan, Saskatoon, Canada
| | | | - Fujun Qin
- Department of Pathology, School of Medicine, University of Virginia, Charlottesville, VA, USA
| | - Md Fahmid Islam
- Department of Pathology and Laboratory Medicine, Cancer Cluster, College of Medicine, University of Saskatchewan, Saskatoon, Canada
| | - Behzad M Toosi
- Department of Pathology and Laboratory Medicine, Cancer Cluster, College of Medicine, University of Saskatchewan, Saskatoon, Canada
| | - Chelsea E Cunningham
- Department of Pathology and Laboratory Medicine, Cancer Cluster, College of Medicine, University of Saskatchewan, Saskatoon, Canada
| | - Darrell D Mousseau
- Cell Signaling Laboratory, Departments of Psychiatry and Physiology, University of Saskatchewan, Saskatoon, Canada
| | - Maruti C Uppalapati
- Department of Pathology and Laboratory Medicine, Cancer Cluster, College of Medicine, University of Saskatchewan, Saskatoon, Canada
| | - Peter C Stirling
- Terry Fox Laboratory, British Columbia Cancer Agency, Vancouver, Canada
| | - Yuliang Wu
- Department of Biochemistry, Cancer Cluster, College of Medicine, University of Saskatchewan, Saskatoon, Canada
| | - Keith Bonham
- Cancer Research, Saskatchewan Cancer Agency, Saskatoon, Canada
| | - Andrew Freywald
- Department of Pathology and Laboratory Medicine, Cancer Cluster, College of Medicine, University of Saskatchewan, Saskatoon, Canada
| | - Hui Li
- Department of Pathology, School of Medicine, University of Virginia, Charlottesville, VA, USA
| | - Franco J Vizeacoumar
- Department of Pathology and Laboratory Medicine, Cancer Cluster, College of Medicine, University of Saskatchewan, Saskatoon, Canada.,Cancer Research, Saskatchewan Cancer Agency, Saskatoon, Canada
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Karole AM, Chodisetty S, Ali A, Kumari N, Tyagi S. Novel sub-cellular localizations and intra-molecular interactions may define new functions of Mixed Lineage Leukemia protein. Cell Cycle 2018; 17:2684-2696. [PMID: 30489191 DOI: 10.1080/15384101.2018.1553338] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022] Open
Abstract
Mixed-lineage leukemia (MLL) protein is the best-characterized member of SET family of histone 3 lysine 4 methyltransferase, known for its transcriptional-activation role during development. mll gene rearrangements cause multiple kinds of aggressive leukemia in both children and adults. An important 'first' step in understanding the role of MLL in leukemogenesis would be to identify its localization throughout the cell cycle. In order to fully understand the breath of MLL functions in proliferating cells, we have analyzed its sub-cellular localization during the cell cycle. Our results show that MLL localizes to nucleolus and centrosome in interphase. During mitosis, it localizes to centrosomes and midbody in addition to previously reported spindle apparatus. Our results show that MLLN is required to translocate MLLC to the nucleolus. These finding suggest functional roles for MLL in nucleolus and mitosis. We also show how MLL-fusion proteins (MLL-FPs) localize to the same sub-cellular organelles like endogenous MLL. Our results indicate that MLL-fusion proteins may not only disturb the cell homeostasis by gain-of-function of the chimeric protein, but also by interfering with the functions of endogenous MLL.
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Affiliation(s)
- Amit Mahendra Karole
- a Laboratory of Cell Cycle Regulation , Centre for DNA Fingerprinting and Diagnostics (CDFD) , Uppal , Hyderabad 500039 , India.,b Graduate Studies , Manipal Academy of Higher Education , Manipal , India
| | - Swathi Chodisetty
- a Laboratory of Cell Cycle Regulation , Centre for DNA Fingerprinting and Diagnostics (CDFD) , Uppal , Hyderabad 500039 , India.,b Graduate Studies , Manipal Academy of Higher Education , Manipal , India
| | - Aamir Ali
- a Laboratory of Cell Cycle Regulation , Centre for DNA Fingerprinting and Diagnostics (CDFD) , Uppal , Hyderabad 500039 , India.,b Graduate Studies , Manipal Academy of Higher Education , Manipal , India
| | - Nidhi Kumari
- a Laboratory of Cell Cycle Regulation , Centre for DNA Fingerprinting and Diagnostics (CDFD) , Uppal , Hyderabad 500039 , India
| | - Shweta Tyagi
- a Laboratory of Cell Cycle Regulation , Centre for DNA Fingerprinting and Diagnostics (CDFD) , Uppal , Hyderabad 500039 , India
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Chromatin proteins and RNA are associated with DNA during all phases of mitosis. Cell Discov 2016; 2:16038. [PMID: 27807477 PMCID: PMC5078801 DOI: 10.1038/celldisc.2016.38] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2016] [Accepted: 10/07/2016] [Indexed: 12/11/2022] Open
Abstract
Mitosis brings about major changes to chromosome and nuclear structure. We used recently developed proximity ligation assay-based techniques to investigate the association with DNA of chromatin-associated proteins and RNAs in Drosophila embryos during mitosis. All groups of tested proteins, histone-modifying and chromatin-remodeling proteins and methylated histones remained in close proximity to DNA during all phases of mitosis. We also found that RNA transcripts are associated with DNA during all stages of mitosis. Reduction of H3K27me3 levels or elimination of RNAs had no effect on the association of the components of PcG and TrxG complexes to DNA. Using a combination of proximity ligation assay-based techniques and super-resolution microscopy, we found that the number of protein-DNA and RNA-DNA foci undergoes significant reduction during mitosis, suggesting that mitosis may be accompanied by structural re-arrangement or compaction of specific chromatin domains.
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Gavrilov AA, Razin SV. Compartmentalization of the cell nucleus and spatial organization of the genome. Mol Biol 2015. [DOI: 10.1134/s0026893315010033] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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7
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Ulianov SV, Gavrilov AA, Razin SV. Nuclear Compartments, Genome Folding, and Enhancer-Promoter Communication. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2015; 315:183-244. [DOI: 10.1016/bs.ircmb.2014.11.004] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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8
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Ballabio E, Milne TA. Molecular and Epigenetic Mechanisms of MLL in Human Leukemogenesis. Cancers (Basel) 2012; 4:904-44. [PMID: 24213472 PMCID: PMC3712720 DOI: 10.3390/cancers4030904] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2012] [Revised: 08/31/2012] [Accepted: 09/04/2012] [Indexed: 01/20/2023] Open
Abstract
Epigenetics is often defined as the study of heritable changes in gene expression or chromosome stability that don’t alter the underlying DNA sequence. Epigenetic changes are established through multiple mechanisms that include DNA methylation, non-coding RNAs and the covalent modification of specific residues on histone proteins. It is becoming clear not only that aberrant epigenetic changes are common in many human diseases such as leukemia, but that these changes by their very nature are malleable, and thus are amenable to treatment. Epigenetic based therapies have so far focused on the use of histone deacetylase (HDAC) inhibitors and DNA methyltransferase inhibitors, which tend to have more general and widespread effects on gene regulation in the cell. However, if a unique molecular pathway can be identified, diseases caused by epigenetic mechanisms are excellent candidates for the development of more targeted therapies that focus on specific gene targets, individual binding domains, or specific enzymatic activities. Designing effective targeted therapies depends on a clear understanding of the role of epigenetic mutations during disease progression. The Mixed Lineage Leukemia (MLL) protein is an example of a developmentally important protein that controls the epigenetic activation of gene targets in part by methylating histone 3 on lysine 4. MLL is required for normal development, but is also mutated in a subset of aggressive human leukemias and thus provides a useful model for studying the link between epigenetic cell memory and human disease. The most common MLL mutations are chromosome translocations that fuse the MLL gene in frame with partner genes creating novel fusion proteins. In this review, we summarize recent work that argues MLL fusion proteins could function through a single molecular pathway, but we also highlight important data that suggests instead that multiple independent mechanisms underlie MLL mediated leukemogenesis.
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Affiliation(s)
- Erica Ballabio
- MRC Molecular Haematology Unit, Weatherall Institute of Molecular Medicine, John Radcliffe Hospital Headington, Oxford OX3 9DS, UK.
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A human ESC model for MLL-AF4 leukemic fusion gene reveals an impaired early hematopoietic-endothelial specification. Cell Res 2012; 22:986-1002. [PMID: 22212479 DOI: 10.1038/cr.2012.4] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The MLL-AF4 fusion gene is a hallmark genomic aberration in high-risk acute lymphoblastic leukemia in infants. Although it is well established that MLL-AF4 arises prenatally during human development, its effects on hematopoietic development in utero remain unexplored. We have created a human-specific cellular system to study early hemato-endothelial development in MLL-AF4-expressing human embryonic stem cells (hESCs). Functional studies, clonal analysis and gene expression profiling reveal that expression of MLL-AF4 in hESCs has a phenotypic, functional and gene expression impact. MLL-AF4 acts as a global transcriptional activator and a positive regulator of homeobox gene expression in hESCs. Functionally, MLL-AF4 enhances the specification of hemogenic precursors from hESCs but strongly impairs further hematopoietic commitment in favor of an endothelial cell fate. MLL-AF4 hESCs are transcriptionally primed to differentiate towards hemogenic precursors prone to endothelial maturation, as reflected by the marked upregulation of master genes associated to vascular-endothelial functions and early hematopoiesis. Furthermore, we report that MLL-AF4 expression is not sufficient to transform hESC-derived hematopoietic cells. This work illustrates how hESCs may provide unique insights into human development and further our understanding of how leukemic fusion genes, known to arise prenatally, regulate human embryonic hematopoietic specification.
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Enforced expression of MLL-AF4 fusion in cord blood CD34+ cells enhances the hematopoietic repopulating cell function and clonogenic potential but is not sufficient to initiate leukemia. Blood 2011; 117:4746-58. [PMID: 21389315 DOI: 10.1182/blood-2010-12-322230] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Infant acute lymphoblastic leukemia harboring the fusion mixed-lineage leukemia (MLL)-AF4 is associated with a dismal prognosis and very brief latency. Our limited understanding of transformation by MLL-AF4 is reflected in murine models, which do not accurately recapitulate the human disease. Human models for MLL-AF4 disease do not exist. Hematopoietic stem or progenitor cells (HSPCs) represent probable targets for transformation. Here, we explored in vitro and in vivo the impact of the enforced expression of MLL-AF4 in human cord blood-derived CD34(+) HSPCs. Intrabone marrow transplantation into NOD/SCID-IL2Rγ(-/-) mice revealed an enhanced multilineage hematopoietic engraftment, efficiency, and homing to other hematopoietic sites on enforced expression of MLL-AF4. Lentiviral transduction of MLL-AF4 into CD34(+) HSPCs increased the in vitro clonogenic potential of CD34(+) progenitors and promoted their proliferation. Consequently, cell cycle and apoptosis analyses suggest that MLL-AF4 conveys a selective proliferation coupled to a survival advantage, which correlates with changes in the expression of genes involved in apoptosis, sensing DNA damage and DNA repair. However, MLL-AF4 expression was insufficient to initiate leukemogenesis on its own, indicating that either additional hits (or reciprocal AF4-MLL product) may be required to initiate ALL or that cord blood-derived CD34(+) HSPCs are not the appropriate cellular target for MLL-AF4-mediated ALL.
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Robinson BW, Germano G, Song Y, Abrams J, Scott M, Guariento I, Tiso N, Argenton F, Basso G, Rhodes J, Kanki JP, Look AT, Balice-Gordon RJ, Felix CA. mll ortholog containing functional domains of human MLL is expressed throughout the zebrafish lifespan and in haematopoietic tissues. Br J Haematol 2010; 152:307-21. [PMID: 21155757 DOI: 10.1111/j.1365-2141.2010.08398.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Infant leukaemia is an embryonal disease in which the underlying MLL translocations initiate in utero. Zebrafish offer unique potential to understand how MLL impacts haematopoiesis from the earliest embryonic timepoints and how translocations cause leukaemia as an embryonal process. In this study, a zebrafish mll cDNA syntenic to human MLL spanning the 5' to 3' UTRs, was cloned from embryos, and mll expression was characterized over the zebrafish lifespan. The protein encoded by the 35-exon ORF exhibited 46·4% overall identity to human MLL and 68-100% conservation in functional domains (AT-hooks, SNL, CXXC, PHD, bromodomain, FYRN, taspase1 sites, FYRC, SET). Maternally supplied transcripts were detected at 0-2 hpf. Strong ubiquitous early zygotic expression progressed to a cephalo-caudal gradient during later embryogenesis. mll was expressed in the intermediate cell mass (ICM) where primitive erythrocytes are produced and in the kidney where definitive haematopoiesis occurs in adults. mll exhibits high cross species conservation, is developmentally regulated in haematopoietic and other tissues and is expressed from the earliest embryonic timepoints throughout the zebrafish lifespan. Haematopoietic tissue expression validates using zebrafish for MLL haematopoiesis and leukaemia models.
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Affiliation(s)
- Blaine W Robinson
- Division of Oncology, The Children's Hospital of Philadelphia, Philadelphia, PA, USA
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12
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Insights into the cellular origin and etiology of the infant pro-B acute lymphoblastic leukemia with MLL-AF4 rearrangement. Leukemia 2010; 25:400-10. [PMID: 21135858 DOI: 10.1038/leu.2010.284] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Infant acute lymphoblastic leukemia (ALL) involving mixed-lineage leukemia (MLL) fusions has attracted a huge interest in basic and clinical research because of its prenatal origin, mixed-lineage phenotype, dismal prognosis and extremely short latency. Over 90% of infant ALLs are pro-B ALL harboring the leukemic fusion MLL-AF4. Despite the fact that major achievements have provided a better understanding about the etiology of infant MLL-AF4+ ALL over the last two decades, key questions remain unanswered. Epidemiological and genetic studies suggest that the in utero origin of MLL rearrangements in infant leukemia may be the result of prenatal exposure to genotoxic compounds. In fact, chronic exposure of human embryonic stem cells (hESCs) to etoposide induces MLL rearrangements and makes hESC more prone to acquire subsequent chromosomal abnormalities than postnatal CD34(+) cells, linking embryonic exposure to topoisomerase II inhibitors to genomic instability and MLL rearrangements. Unfortunately, very little is known about the nature of the target cell for transformation. Neuron-glial antigen 2 expression was initially claimed to be specifically associated with MLL rearrangements and was recently shown to be readily expressed in CD34+CD38+, but not CD34+CD38- cells suggesting that progenitors rather than stem cells may be the target cell for transformation. Importantly, the recent findings showing that MLL-AF4 rearrangement is present and expressed in mesenchymal stem cells from infant patients with MLLAF4+ ALL challenged our current view of the etiology and cellular origin of this leukemia. It becomes therefore crucial to determine where the leukemia relapses come from and how the tumor-stroma relationship is defined at the molecular level. Finally, MLL-AF4 leukemogenesis has been particularly difficult to model and bona fide MLL-AF4 disease models do not exist so far. It is likely that the current disease models are missing some essential ingredients of leukemogenesis in the human embryo/fetus. We thus propose modeling MLL-AF4+ infant pro-B ALL using prenatal hESCs.
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Blobel GA, Kadauke S, Wang E, Lau AW, Zuber J, Chou MM, Vakoc CR. A reconfigured pattern of MLL occupancy within mitotic chromatin promotes rapid transcriptional reactivation following mitotic exit. Mol Cell 2010; 36:970-83. [PMID: 20064463 DOI: 10.1016/j.molcel.2009.12.001] [Citation(s) in RCA: 135] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2009] [Revised: 08/03/2009] [Accepted: 12/03/2009] [Indexed: 02/02/2023]
Abstract
Mixed lineage leukemia (MLL) and its metazoan Trithorax orthologs have been linked with the epigenetic maintenance of transcriptional activity. To identify mechanisms by which MLL perpetuates active transcription in dividing cells, we investigated its role during M phase of the cell cycle. Unlike other chromatin-modifying enzymes examined, we found that MLL associates with gene promoters packaged within condensed mitotic chromosomes. Genome-wide location analysis identified a globally rearranged pattern of MLL occupancy during mitosis in a manner favoring genes that were highly transcribed during interphase. Knockdown experiments revealed that MLL retention at gene promoters during mitosis accelerates transcription reactivation following mitotic exit. MLL tethers Menin, RbBP5, and ASH2L to its occupied sites during mitosis, but is dispensable for preserving histone H3K4 methylation. These findings implicate mitotic bookmarking as a component of Trithorax-based gene regulation, which may facilitate inheritance of active gene expression states during cell division.
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Affiliation(s)
- Gerd A Blobel
- Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11724, USA
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Bueno C, Catalina P, Melen GJ, Montes R, Sánchez L, Ligero G, García-Pérez JL, Menendez P. Etoposide induces MLL rearrangements and other chromosomal abnormalities in human embryonic stem cells. Carcinogenesis 2009; 30:1628-37. [PMID: 19587093 DOI: 10.1093/carcin/bgp169] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
MLL rearrangements are hallmark genetic abnormalities in infant leukemia known to arise in utero. They can be induced during human prenatal development upon exposure to etoposide. We also hypothesize that chronic exposure to etoposide might render cells more susceptible to other genomic insults. Here, for the first time, human embryonic stem cells (hESCs) were used as a model to test the effects of etoposide on human early embryonic development. We addressed whether: (i) low doses of etoposide promote MLL rearrangements in hESCs and hESCs-derived hematopoietic cells; (ii) MLL rearrangements are sufficient to confer hESCs with a selective growth advantage and (iii) continuous exposure to low doses of etoposide induces hESCs to acquire other chromosomal abnormalities. In contrast to cord blood-derived CD34(+) and hESC-derived hematopoietic cells, exposure of undifferentiated hESCs to a single low dose of etoposide induced a pronounced cell death. Etoposide induced MLL rearrangements in hESCs and their hematopoietic derivatives. After long-term culture, the proportion of hESCs harboring MLL rearrangements diminished and neither cell cycle variations nor genomic abnormalities were observed in the etoposide-treated hESCs, suggesting that MLL rearrangements are insufficient to confer hESCs with a selective proliferation/survival advantage. However, continuous exposure to etoposide induced MLL breaks and primed hESCs to acquire other major karyotypic abnormalities. These data show that chronic exposure of developmentally early stem cells to etoposide induces MLL rearrangements and make hESCs more prone to acquire other chromosomal abnormalities than postnatal CD34(+) cells, linking embryonic genotoxic exposure to genomic instability.
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Affiliation(s)
- Clara Bueno
- Andalusian Stem Cell Bank, Centro de Investigación Biomédica, Parque Tecnológico de la Salud, University of Granada, Granada 18100 Spain
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Abstract
Mixed lineage leukemia is a very aggressive blood cancer that predominantly occurs in pediatric patients. In contrast to other types of childhood acute leukemias, mixed lineage leukemia presents with a dismal prognosis and despite the availability of advanced treatment methods cure rates have stagnated over the last years. Mixed lineage leukemia is characterized by the presence of MLL fusion proteins that are the result of chromosomal translocations affecting the MLL gene at 11q23. These events juxtapose the amino-terminus of the histone methyltransferase MLL with a variety of different fusion partners that destroy normal histone methyltransferase function of MLL and replace it by heterologous functions contributed by the fusion partner. The resulting chimeras are transcriptional regulators that take control of targets normally controlled by MLL with the clustered HOX homeobox genes as prominent examples. Recent studies suggested that MLL fusion partners activate transcription by two different mechanisms. Some of these proteins are themselves chromatin modifiers that introduce histone acetylation whereas other fusion partners can recruit histone methyltransferases. In particular, histone H3 specific methylation at lysine 79 catalyzed by DOT1L has been recognized as a hallmark of chromatin activated by MLL fusion proteins. Interestingly, several frequent MLL fusion partners seem to coordinate DOT1L activity with a protein complex that stimulates the elongation phase of transcription by phosphorylating the carboxy-terminal repeat domain of RNA polymerase II. The discovery of these novel enzymatic activities that are essentially involved in MLL fusion protein function presents potential new targets for a rational drug development.
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Affiliation(s)
- Robert K Slany
- Department of Genetics, University Erlangen, Erlangen, Germany.
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MLL associates with telomeres and regulates telomeric repeat-containing RNA transcription. Mol Cell Biol 2009; 29:4519-26. [PMID: 19528237 DOI: 10.1128/mcb.00195-09] [Citation(s) in RCA: 96] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Mammalian telomeres consist of TTAGGG repeats organized in nucleosomes and associated with a six-protein complex known as shelterin, which preserves telomere structure and protects chromosome ends from the cellular DNA damage response. Recent studies have found that telomeres are transcribed into telomeric UUAGGG repeat-containing RNA (TERRA) starting from subtelomeric regions. TERRA binding at telomeres appears to be involved in cis-based mechanisms of telomeric chromatin organization and maintenance. A number of histone methyltransferases (HMTs) are known to influence telomeric chromatin status; however, the regulatory mechanisms of telomere transcription are poorly understood. Here, we show that the histone 3/lysine 4 (H3/K4) HMT and the transcriptional regulator MLL associate with telomeres and contribute to their H3/K4 methylation and transcription in a telomere length-dependent manner. In human diploid fibroblasts, RNA interference-mediated MLL depletion affects telomere chromatin modification and transcription and induces the telomere damage response. Telomere uncapping through either TRF2 shelterin protein knockdown or exposure to telomere G-strand DNA oligonucleotides significantly increases the transcription of TERRA, an effect mediated by the functional cooperation between MLL and the tumor suppressor p53. In total, our findings identify a previously unrecognized role of MLL in modifying telomeric chromatin and provide evidence for the functional interaction between MLL, p53, and the shelterin complex in the regulation of telomeric transcription and stability.
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Horiguchi K, Yamada M, Satoh T, Hashimoto K, Hirato J, Tosaka M, Yamada S, Mori M. Transcriptional Activation of the Mixed Lineage Leukemia–p27Kip1 Pathway by a Somatostatin Analogue. Clin Cancer Res 2009; 15:2620-9. [DOI: 10.1158/1078-0432.ccr-08-2473] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Caslini C, Yang Z, El-Osta M, Milne TA, Slany RK, Hess JL. Interaction of MLL amino terminal sequences with menin is required for transformation. Cancer Res 2007; 67:7275-83. [PMID: 17671196 PMCID: PMC7566887 DOI: 10.1158/0008-5472.can-06-2369] [Citation(s) in RCA: 148] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Rearrangements of the mixed lineage leukemia gene MLL are associated with aggressive lymphoid and myeloid leukemias. The resulting MLL fusion proteins enforce high-level expression of HOX genes and the HOX cofactor MEIS1, which is pivotal for leukemogenesis. Both wild-type MLL and MLL fusion proteins interact with the tumor suppressor menin and with the Hoxa9 locus in vivo. Here, we show that MLL sequences between amino acids 5 and 44 are required for interaction with menin and for the transformation of hematopoietic progenitors. Blocking the MLL-menin interaction by the expression of a dominant negative inhibitor composed of amino terminal MLL sequences down-regulates Meis1 expression and inhibits cell proliferation, suggesting that targeting this interaction may be an effective therapeutic strategy for leukemias with MLL rearrangements.
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Affiliation(s)
- Corrado Caslini
- Department of Pathology, University of Michigan Medical School, Ann Arbor, Michigan
| | - Zhaohai Yang
- Department of Pathology, University of Alabama, Birmingham, Alabama
| | - Mohamad El-Osta
- Department of Pathology, University of Michigan Medical School, Ann Arbor, Michigan
| | - Thomas A. Milne
- Laboratory of Biochemistry and Molecular Biology, The Rockefeller University, New York, New York
| | - Robert K. Slany
- Department of Genetics, University of Erlangen, Erlangen, Germany
| | - Jay L. Hess
- Department of Pathology, University of Michigan Medical School, Ann Arbor, Michigan
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19
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Yocum AK, Busch CM, Felix CA, Blair IA. Proteomics-based strategy to identify biomarkers and pharmacological targets in leukemias with t(4;11) translocations. J Proteome Res 2006; 5:2743-53. [PMID: 17022645 DOI: 10.1021/pr060235v] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Translocations and other aberrations involving the MLL (mixed lineage leukemia) gene result in aggressive forms of leukemias. Heterogeneity in partner genes, in chromosomal breakpoints, in MLL itself, and in the different partner genes results in heterogeneous fusion transcripts that can be alternatively spliced, which complicates deciphering a unifying mechanism of leukemogenesis. However, recent microarray studies completed with clinical leukemia specimens have uncovered several distinct mRNA signatures within MLL leukemia that differ from other types of leukemia. A global proteomics strategy using MV4-11 and RS4:11 cells in culture was employed to investigate possible protein signatures common to different MLL leukemias and to identify disease biomarkers and protein targets for pharmacological intervention. Initial proteomics screening experiments with two-dimensional differential in-gel electrophoresis revealed heat shock protein 90 alpha (HSP90alpha) as a potential target for pharmacological inhibition and nucleoside diphosphate kinase (nm23) as a biomarker for measuring treatment efficacy. Using a modified stable isotope labeling of amino acids in cell culture (SILAC) approach, coupled with two-dimensional liquid chromatography tandem mass spectrometry (2D-LC-MS/MS), changes in abundance for over 500 proteins were measured. In addition, decreased expression of the novel biomarker nm23 was observed during HSP90 inhibition with 17-allylamino-17-demethoxygeldanamycin (17-AAG) in the MV4-11 cell line. The present study validates the use of a global proteomics strategy to uncover novel biomarkers and pharmacological targets for leukemias with MLL translocations. Additionally, several proteins were found to be expressed in concordance with microarray studies of mRNA expression in specimens from patients showing the value in comparing mRNA transcript and proteomic profiles. This work represents one of the most comprehensive proteomics screens of MLL leukemias that have been conducted to date.
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MESH Headings
- Amino Acid Sequence
- Benzoquinones/pharmacology
- Benzoquinones/therapeutic use
- Biomarkers, Tumor/analysis
- Biomarkers, Tumor/genetics
- Chromosomes, Human, Pair 11/genetics
- Chromosomes, Human, Pair 4/genetics
- Electrophoresis, Gel, Two-Dimensional
- HSP90 Heat-Shock Proteins/analysis
- Humans
- Lactams, Macrocyclic/pharmacology
- Lactams, Macrocyclic/therapeutic use
- Leukemia/diagnosis
- Leukemia/drug therapy
- Leukemia/genetics
- Mass Spectrometry
- Molecular Sequence Data
- Myeloid-Lymphoid Leukemia Protein/genetics
- Neoplasm Proteins/analysis
- Neoplasm Proteins/genetics
- Nucleoside-Diphosphate Kinase/analysis
- Proteome/analysis
- Proteome/genetics
- Proteomics/methods
- Translocation, Genetic
- Tumor Cells, Cultured
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Affiliation(s)
- Anastasia K Yocum
- Center for Cancer Pharmacology, University of Pennsylvania School of Medicine, and Division of Oncology, The Children's Hospital of Philadelphia, Department of Pediatrics, Pennsylvania 19104-4318, USA
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20
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Horton SJ, Grier DG, McGonigle GJ, Thompson A, Morrow M, De Silva I, Moulding DA, Kioussis D, Lappin TRJ, Brady HJM, Williams O. Continuous MLL-ENL expression is necessary to establish a "Hox Code" and maintain immortalization of hematopoietic progenitor cells. Cancer Res 2005; 65:9245-52. [PMID: 16230385 DOI: 10.1158/0008-5472.can-05-1691] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The t[(11;19)(p22;q23)] translocation, which gives rise to the MLL-ENL fusion protein, is commonly found in infant acute leukemias of both the myeloid and lymphoid lineage. To investigate the molecular mechanism of immortalization by MLL-ENL we established a Tet-regulatable system of MLL-ENL expression in primary hematopoietic progenitor cells. Immortalized myeloid cell lines were generated, which are dependent on continued MLL-ENL expression for their survival and proliferation. These cells either terminally differentiate or die when MLL-ENL expression is turned off with doxycycline. The expression profile of all 39 murine Hox genes was analyzed in these cells by real-time quantitative PCR. This analysis showed that loss of MLL-ENL was accompanied by a reduction in the expression of multiple Hoxa genes. By comparing these changes with Hox gene expression in cells induced to differentiate with granulocyte colony-stimulating factor, we show for the first time that reduced Hox gene expression is specific to loss of MLL-ENL and is not a consequence of differentiation. Our data also suggest that the Hox cofactor Meis-2 can substitute for Meis-1 function. Thus, MLL-ENL is required to initiate and maintain immortalization of myeloid progenitors and may contribute to leukemogenesis by aberrantly sustaining the expression of a "Hox code" consisting of Hoxa4 to Hoxa11.
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Affiliation(s)
- Sarah J Horton
- Molecular Haematology and Cancer Biology Unit, Institute of Child Health, University College London
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21
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Wiederschain D, Kawai H, Shilatifard A, Yuan ZM. Multiple mixed lineage leukemia (MLL) fusion proteins suppress p53-mediated response to DNA damage. J Biol Chem 2005; 280:24315-21. [PMID: 15851483 DOI: 10.1074/jbc.m412237200] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Chromosomal translocations involving the mixed lineage leukemia (MLL) gene are often observed in acute leukemias of both myeloid and lymphocytic origin. Expression of MLL fusion proteins is known to induce malignant transformation of normal blood progenitors; however, molecular mechanisms of this process are still poorly understood. In this study we investigated the effect of several frequently detected MLL fusion proteins on p53 transcriptional activity. Our data show that MLL-AF9, MLL-AF10, MLL-ENL, and MLL-ELL substantially down-regulate p53-mediated induction of p21, MDM2, and Bax in response to DNA damage. Furthermore, we identify the reduction in p53 acetylation by p300 as a major mechanism of the inhibitory effect of MLL leukemic fusions. Our data suggest that abrogation of p53 functional activity can be a common feature of MLL fusion-mediated leukemogenesis.
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MESH Headings
- Blotting, Western
- Cell Line, Tumor
- DNA Damage
- DNA Primers/chemistry
- Humans
- Immunoprecipitation
- Luciferases/metabolism
- Models, Genetic
- Myeloid-Lymphoid Leukemia Protein
- Oncogene Proteins, Fusion/chemistry
- Oncogene Proteins, Fusion/metabolism
- Oncogene Proteins, Fusion/physiology
- Plasmids/metabolism
- Protein Structure, Tertiary
- RNA/chemistry
- Radiation, Ionizing
- Recombinant Fusion Proteins/chemistry
- Retroviridae/genetics
- Reverse Transcriptase Polymerase Chain Reaction
- Transcription, Genetic
- Transcriptional Activation
- Transfection
- Translocation, Genetic
- Tumor Suppressor Protein p53/metabolism
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Affiliation(s)
- Dmitri Wiederschain
- Department of Genetics and Complex Diseases, Harvard School of Public Health, Boston, Massachusetts 02115, USA
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22
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Ralph SA, Scheidig-Benatar C, Scherf A. Antigenic variation in Plasmodium falciparum is associated with movement of var loci between subnuclear locations. Proc Natl Acad Sci U S A 2005; 102:5414-9. [PMID: 15797990 PMCID: PMC556247 DOI: 10.1073/pnas.0408883102] [Citation(s) in RCA: 159] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2004] [Indexed: 11/18/2022] Open
Abstract
Much of the success of Plasmodium falciparum in establishing persistent infections is attributed to immune evasion through antigenic variation. This process involves periodically exchanging variants of the major surface antigen PfEMP1, a protein also responsible for parasite cytoadherence. PfEMP1 is encoded by genes of the 60-member var family, located at subtelomeric and internal chromosome loci. The active or silenced state of var genes is heritable, and its control by nonsequence information remains puzzling. Using FISH analysis, we demonstrate that both internal and subtelomeric var genes are positioned at the nuclear periphery in their repressed state. Upon activation, the same var genes are still found in the periphery, indicating that this zone can be transcriptionally competent, rather than uniformly silenced. However, activation of a var gene is linked with altered positioning at the nuclear periphery, with subtelomeric var loci exiting chromosome end clusters and being relocated to distinct nuclear sites. Serial sectioning of parasite nuclei reveals areas of both condensed and noncondensed chromatin at the nuclear periphery. Our results demonstrate that regulation of antigenic variation is associated with subnuclear position effects and point to the existence of transcriptionally permissive perinuclear zones for var genes.
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Affiliation(s)
- Stuart A Ralph
- Institut Pasteur, Centre National de la Recherche Scientifique, Unité de Recherche Associée 2581, 25 Rue du Docteur Roux, F-75724 Paris Cedex 15, France
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23
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Okada Y, Feng Q, Lin Y, Jiang Q, Li Y, Coffield VM, Su L, Xu G, Zhang Y. hDOT1L Links Histone Methylation to Leukemogenesis. Cell 2005; 121:167-78. [PMID: 15851025 DOI: 10.1016/j.cell.2005.02.020] [Citation(s) in RCA: 612] [Impact Index Per Article: 32.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2004] [Revised: 02/13/2005] [Accepted: 02/17/2005] [Indexed: 12/01/2022]
Abstract
Epigenetic modifications play an important role in human cancer. One such modification, histone methylation, contributes to human cancer through deregulation of cancer-relevant genes. The yeast Dot1 and its human counterpart, hDOT1L, methylate lysine 79 located within the globular domain of histone H3. Here we report that hDOT1L interacts with AF10, an MLL (mixed lineage leukemia) fusion partner involved in acute myeloid leukemia, through the OM-LZ region of AF10 required for MLL-AF10-mediated leukemogenesis. We demonstrate that direct fusion of hDOT1L to MLL results in leukemic transformation in an hDOT1L methyltransferase activity-dependent manner. Transformation by MLL-hDOT1L and MLL-AF10 results in upregulation of a number of leukemia-relevant genes, such as Hoxa9, concomitant with hypermethylation of H3-K79. Our studies thus establish that mistargeting of hDOT1L to Hoxa9 plays an important role in MLL-AF10-mediated leukemogenesis and suggests that the enzymatic activity of hDOT1L may provide a potential target for therapeutic intervention.
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Affiliation(s)
- Yuki Okada
- Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
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24
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Wang J, Iwasaki H, Krivtsov A, Febbo PG, Thorner AR, Ernst P, Anastasiadou E, Kutok JL, Kogan SC, Zinkel SS, Fisher JK, Hess JL, Golub TR, Armstrong SA, Akashi K, Korsmeyer SJ. Conditional MLL-CBP targets GMP and models therapy-related myeloproliferative disease. EMBO J 2005; 24:368-81. [PMID: 15635450 PMCID: PMC545811 DOI: 10.1038/sj.emboj.7600521] [Citation(s) in RCA: 98] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2004] [Accepted: 11/24/2004] [Indexed: 11/09/2022] Open
Abstract
Chromosomal translocations that fuse the mixed lineage leukemia (MLL) gene with multiple partners typify acute leukemias of infancy as well as therapy-related leukemias. We utilized a conditional knockin strategy to bypass the embryonic lethality caused by MLL-CBP expression and to assess the immediate effects of induced MLL-CBP expression on hematopoiesis. Within days of activating MLL-CBP, the fusion protein selectively expanded granulocyte/macrophage progenitors (GMP) and enhanced their self-renewal/proliferation. MLL-CBP altered the gene expression program of GMP, upregulating a subset of genes including Hox a9. Inhibition of Hox a9 expression by RNA interference demonstrated that MLL-CBP required Hox a9 for its enhanced cell expansion. Following exposure to sublethal gamma-irradiation or N-ethyl-N-nitrosourea (ENU), MLL-CBP mice developed myelomonocytic hyperplasia and progressed to fatal myeloproliferative disorders. These represented the spectrum of therapy-induced acute myelomonocytic leukemia/chronic myelomonocytic leukemia/myelodysplastic/myeloproliferative disorder similar to that seen in humans possessing the t(11;16). This model of MLL-CBP therapy-related myeloproliferative disease demonstrates the selectivity of this MLL fusion for GMP cells and its ability to initiate leukemogenesis in conjunction with cooperating mutations.
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Affiliation(s)
- Jing Wang
- Department of Pathology and Medicine, Howard Hughes Medical Institute, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA, USA
| | - Hiromi Iwasaki
- Department of Pathology, Harvard Medical School, Dana-Farber Cancer Institute, Boston, MA, USA
| | - Andrei Krivtsov
- Division of Hematology/Oncology, Children's Hospital, Boston, MA, USA
| | - Phillip G Febbo
- Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, MA, USA
| | - Aaron R Thorner
- Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, MA, USA
| | - Patricia Ernst
- Department of Pathology and Medicine, Howard Hughes Medical Institute, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA, USA
| | - Ema Anastasiadou
- Harvard Institutes of Medicine, Harvard Medical School, Boston, MA, USA
| | - Jeffery L Kutok
- Department of Pathology, Harvard Medical School, Dana-Farber Cancer Institute, Boston, MA, USA
| | - Scott C Kogan
- Comprehensive Cancer Center and Department of Laboratory Medicine, University of California, San Francisco, CA, USA
| | - Sandra S Zinkel
- Department of Pathology and Medicine, Howard Hughes Medical Institute, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA, USA
| | - Jill K Fisher
- Department of Pathology and Medicine, Howard Hughes Medical Institute, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA, USA
| | - Jay L Hess
- Department of Pathology and Laboratory Medicine, University of Pennsylvania School of Medicine, Philadelphia, PA, USA
| | - Todd R Golub
- Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, MA, USA
| | - Scott A Armstrong
- Division of Hematology/Oncology, Children's Hospital, Boston, MA, USA
| | - Koichi Akashi
- Department of Pathology, Harvard Medical School, Dana-Farber Cancer Institute, Boston, MA, USA
| | - Stanley J Korsmeyer
- Department of Pathology and Medicine, Howard Hughes Medical Institute, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA, USA
- Howard Hughes Medical Institute, Dana-Farber Cancer Institute, 44 Binney Street, Boston, MA 02115, USA. Tel.: +1 617 632 6402; Fax: +1 617 632 6401; E-mail:
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25
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Abstract
Rearrangements of the MLL gene (ALL1, HRX, and Hrtx) located at chromosome band 11q23 are commonly involved in adult and pediatric cases of primary acute leukemias and also found in cases of therapy-related secondary leukemias. Studies on mouse models of MLL translocation and cell lines containing MLL rearrangements showed that the MLL gene linked chromosomal rearrangements to cellular differentiation and tumor tropism. Moreover, recent structural/functional studies on MLL and aberrant MLL proteins provided new clues and suggested that different mechanisms might be included in leukemogenesis by MLL rearrangements. The connection between these different mechanisms will help us understand globally how aberrant MLL oncogenes affect the normal cellular processes at molecular level.
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Affiliation(s)
- Z-Y Li
- National Laboratory of Medical Molecular Biology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences and Peking Union Medical College, 5 Dong Dan San Tiao, Beijing, PR China
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26
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Elia L, Gottardi E, Floriddia G, Grillo R, Ciambelli F, Luciani M, Chiusolo P, Invernizzi R, Meloni G, Foà R, Saglio G, Cimino G. Retrospective comparison of qualitative and quantitative reverse transcriptase polymerase chain reaction in diagnosing and monitoring the ALL1-AF4 fusion transcript in patients with acute lymphoblastic leukaemia. Leukemia 2004; 18:1824-30. [PMID: 15318246 DOI: 10.1038/sj.leu.2403448] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
We compared quantitative reverse transcriptase polymerase chain reaction (Q-RT-PCR) to qualitative RT-PCR in determining response to therapy and predicting clinical outcome in 18 retrospectively selected patients with ALL positive for the ALL1-AF4 fusion and with frozen RNA samples collected at diagnosis and during follow-up (96 samples analysed). The ALL1-AF4 junction was detected by qualitative RT-PCR in 18 patients and by Q-RT-PCR in 17 patients (one patient harboured the rare e10-e6 ALL1-AF4 junction, which falls outside of the primer and probe location designed for the Q-RT-PCR). In three of the 12 patients negative to qualitative RT-PCR after induction therapy, a small number of ALL1-AF4 copies was detected by Q-RT-PCR. Thus nine patients were negative and eight positive. Seven of the eight positive patients suffered a relapse, including two of the three patients positive to Q-RT-PCR yet negative to qualitative RT-PCR. Moreover, we found two (5%) discordant results among the 39 follow-up tests of the nine patients who converted to a negative qualitative-quantitative PCR status. The results suggest that qualitative RT-PCR is more appropriate for the routine diagnosis of this genetic alteration. However, Q-RT-PCR is more accurate in assessing the molecular response after induction treatment and could be more useful in clinical decision-making in ALL1-AF4-positive ALL patients.
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Affiliation(s)
- L Elia
- Department of Cellular Biotechnology and Haematology, La Sapienza University, Rome, Italy
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27
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Caslini C, Serna A, Rossi V, Introna M, Biondi A. Modulation of cell cycle by graded expression of MLL-AF4 fusion oncoprotein. Leukemia 2004; 18:1064-71. [PMID: 14990976 DOI: 10.1038/sj.leu.2403321] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Acute lymphoblastic leukemia (ALLs) expressing MLL-AF4, the fusion product of t(4;11)(q21;q23), show marked leucocytosis and extramedullary disease in multiple organs, respond poorly to chemotherapy and have poor prognosis. In vitro, leukemic cells with the t(4;11) show resistance to serum deprivation-induced or interferon gamma-regulated CD95-mediated apoptosis. In addition, t(4;11) cells have prolonged doubling time and lower percentage of cells in cycle compared to non-t(4;11) B lineage cell lines. In this study, we examine the time- and level-dependent effects of MLL-AF4 conditional expression on cell cycle and differentiation of myelomonocytic leukemia cell line U937. By varying the concentration of tetracycline in growth media, we found that increasing levels of MLL-AF4 expression result in a progressive decrease in growth rate and fraction of S phase cells, paralleled by an increase in percentage of cells expressing CD11b. Our results demonstrate a dosage-dependent effect of MLL-AF4 fusion oncoprotein on cell cycle progression, with increasing expression levels resulting in the accumulation in G1, prolonged doubling time, both findings that might be responsible for the increased resistance to etoposide-mediated cytotoxicity. We propose the cell cycle control exerted by MLL-AF4 may be responsible of resistance to cell-death promoting stimuli in leukemia carrying the t(4;11) translocation.
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Affiliation(s)
- C Caslini
- Centro Ricerche M Tettamanti, Clinica Pediatrica Università Milano-Bicocca, Monza, Italy
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28
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Eguchi M, Eguchi-Ishimae M, Greaves M. The small oligomerization domain of gephyrin converts MLL to an oncogene. Blood 2004; 103:3876-82. [PMID: 14751928 DOI: 10.1182/blood-2003-11-3817] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
AbstractThe MLL (mixed lineage leukemia) gene forms chimeric fusions with a diverse set of partner genes as a consequence of chromosome translocations in leukemia. In several fusion partners, a transcriptional activation domain appears to be essential for conferring leukemogenic capacity on MLL protein. Other fusion partners, however, lack such domains. Here we show that gephyrin (GPHN), a neuronal receptor assembly protein and rare fusion partner of MLL in leukemia, has the capacity as an MLL-GPHN chimera to transform hematopoietic progenitors, despite lack of transcriptional activity. A small 15–amino acid tubulin-binding domain of GPHN is necessary and sufficient for this activity in vitro and in vivo. This domain also confers oligomerization capacity on MLL protein, suggesting that such activity may contribute critically to leukemogenesis. The transduction of MLL-GPHN into hematopoietic progenitor cells caused myeloid and lymphoid lineage leukemias in mice, suggesting that MLL-GPHN can target multipotent progenitor cells. Our results, and other recent data, provide a mechanism for oncogenic conversion of MLL by fusion partners encoding cytoplasmic proteins.
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Affiliation(s)
- Mariko Eguchi
- Leukaemia Research Fund Centre, Institute of Cancer Research, Chester Beatty Laboratories, London, United Kingdom
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29
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Abstract
The MLL gene is a major player in leukemia, particularly in infant leukemia and in secondary, therapy-related acute leukemia. The normal MLL gene plays a key role in developmental regulation of gene expression (including HOX genes), and in leukemia this function is subverted by breakage, recombination, and chimeric fusion with one of 40 or more alternative partner genes. In infant leukemias, the chromosome translocations involving MLL arise during fetal hematopoiesis, possibly in a primitive lymphomyeloid stem cell. In general, these leukemias have a very poor prognosis. The malignancy of these leukemias is all the more dramatic considering their very short preclinical natural history or latency. These data raise fundamental issues of how such divergent MLL chimeric genes transform cells, why they so rapidly evolve to a malignant status, and what alternative or novel therapeutic strategies might be considered. We review here progress in tackling these questions.
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MESH Headings
- Acute Disease
- Age of Onset
- Animals
- Antineoplastic Agents/pharmacology
- Antineoplastic Agents/therapeutic use
- Cell Transformation, Neoplastic/genetics
- Chromosomes, Human, Pair 11/genetics
- Chromosomes, Human, Pair 11/ultrastructure
- DNA-Binding Proteins/chemistry
- DNA-Binding Proteins/genetics
- DNA-Binding Proteins/physiology
- Disease Progression
- Drug Design
- Histone-Lysine N-Methyltransferase
- Humans
- Infant
- Infant, Newborn
- Leukemia, Myeloid/drug therapy
- Leukemia, Myeloid/embryology
- Leukemia, Myeloid/epidemiology
- Leukemia, Myeloid/genetics
- Mice
- Mice, Knockout
- Myeloid-Lymphoid Leukemia Protein
- Oligonucleotide Array Sequence Analysis
- Oncogene Proteins, Fusion/chemistry
- Oncogene Proteins, Fusion/genetics
- Proto-Oncogenes
- Structure-Activity Relationship
- Transcription Factors
- Translocation, Genetic
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Affiliation(s)
- Mariko Eguchi
- LRF Centre for Cell and Molecular Biology of Leukaemia, Institute of Cancer Research, London, UK
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30
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Yam JWP, Jin DY, So CW, Chan LC. Identification and characterization of EBP, a novel EEN binding protein that inhibits Ras signaling and is recruited into the nucleus by the MLL-EEN fusion protein. Blood 2004; 103:1445-53. [PMID: 14551139 DOI: 10.1182/blood-2003-07-2452] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
AbstractThe chimeric MLL-EEN fusion protein is created as a result of chromosomal translocation t(11;19)(q23;p13). EEN, an Src homology 3 (SH3) domain–containing protein in the endophilin family, has been implicated in endocytosis, although little is known about its role in leukemogenesis mediated by the MLL-EEN fusion protein. In this study, we have identified and characterized EBP, a novel EEN binding protein that interacts with the SH3 domain of EEN through a proline-rich motif PPERP. EBP is a ubiquitous protein that is normally expressed in the cytoplasm but is recruited to the nucleus by MLL-EEN with a punctate localization pattern characteristic of the MLL chimeric proteins. EBP interacts simultaneously with EEN and Sos, a guanine-nucleotide exchange factor for Ras. Coexpressoin of EBP with EEN leads to suppression of Ras-induced cellular transformation and Ras-mediated activation of Elk-1. Taken together, our findings suggest a new mechanism for MLL-EEN–mediated leukemogenesis in which MLL-EEN interferes with the Ras-suppressing activities of EBP through direct interaction.
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31
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Erfurth F, Hemenway CS, de Erkenez AC, Domer PH. MLL fusion partners AF4 and AF9 interact at subnuclear foci. Leukemia 2003; 18:92-102. [PMID: 14603337 DOI: 10.1038/sj.leu.2403200] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The MLL gene is involved in translocations associated with both acute lymphoblastic and acute myelogenous leukemia. These translocations fuse MLL with one of over 30 partner genes. Collectively, the MLL partner genes do not share a common structural motif or biochemical function. We have identified a protein interaction between the two most common MLL fusion partners AF4 and AF9. This interaction is restricted to discrete nuclear foci we have named 'AF4 bodies'. The AF4 body is non-nucleolar and is not coincident with any known nuclear structures we have examined. The AF4-AF9 interaction is maintained by the MLL-AF4 fusion protein, and expression of the MLL-AF4 fusion can alter the subnuclear localization of AF9. In view of other research indicating that other MLL fusion partners also interact with one another, these results suggest that MLL fusion partners may participate in a web of protein interactions with a common functional goal. The disruption of this web of interactions by fusion with MLL may be important to leukemogenesis.
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Affiliation(s)
- F Erfurth
- Department of Pathology, The University of Chicago, Chicago, IL, USA.
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32
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Macrini CMT, Pombo-de-Oliveira MS, Ford AM, Alves G. MLL AT-hook sequence is strongly conserved in infant acute leukemia with or without MLL gene rearrangement. Leukemia 2003; 17:1432-3. [PMID: 12835743 DOI: 10.1038/sj.leu.2402966] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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33
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Nie Z, Yan Z, Chen EH, Sechi S, Ling C, Zhou S, Xue Y, Yang D, Murray D, Kanakubo E, Cleary ML, Wang W. Novel SWI/SNF chromatin-remodeling complexes contain a mixed-lineage leukemia chromosomal translocation partner. Mol Cell Biol 2003; 23:2942-52. [PMID: 12665591 PMCID: PMC152562 DOI: 10.1128/mcb.23.8.2942-2952.2003] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
The SWI/SNF family of chromatin-remodeling complexes has been discovered in many species and has been shown to regulate gene expression by assisting transcriptional machinery to gain access to their sites in chromatin. Several complexes of this family have been reported for humans. In this study, two additional complexes are described that belong to the same SWI/SNF family. These new complexes contain as many as eight subunits identical to those found in other SWI/SNF complexes, and they possess a similar ATP-dependent nucleosome disruption activity. But unlike known SWI/SNFs, the new complexes are low in abundance and contain an extra subunit conserved between human and yeast SWI/SNF complexes. This subunit, ENL, is a homolog of the yeast SWI/SNF subunit, ANC1/TFG3. Moreover, ENL is a fusion partner for the gene product of MLL that is a common target for chromosomal translocations in human acute leukemia. The resultant MLL-ENL fusion protein associates and cooperates with SWI/SNF complexes to activate transcription of the promoter of HoxA7, a downstream target essential for oncogenic activity of MLL-ENL. Our data suggest that human SWI/SNF complexes show considerable heterogeneity, and one or more may be involved in the etiology of leukemia by cooperating with MLL fusion proteins.
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Affiliation(s)
- Zuqin Nie
- Laboratory of Genetics, National Institute on Aging, National Institutes of Health, Baltimore, Maryland 21224, USA
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Lee JH, Skalnik DG. CpG-binding protein is a nuclear matrix- and euchromatin-associated protein localized to nuclear speckles containing human trithorax. Identification of nuclear matrix targeting signals. J Biol Chem 2002; 277:42259-67. [PMID: 12200428 DOI: 10.1074/jbc.m205054200] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
CpG-binding protein (CGBP) binds unmethylated CpG dinucleotides and is essential for mammalian development. CGBP exhibits a punctate nuclear localization correlated with 4,6-diamidino-2-phenylindole light regions and is excluded from metaphase chromosomes. The distribution of CGBP is distinct from the heterochromatin-associated proteins MBD1, methyl-CpG-binding protein 2, and HP1alpha. Some CGBP-containing nuclear speckles co-localize with splicing factor SC-35 and actively transcribed regions of the genome, whereas most CGBP co-localizes with acetylated histones, indicating that CGBP is localized to active chromatin. CGBP contains two nuclear localization signals that are insufficient to direct punctate subnuclear distribution. Instead, localization of CGBP to nuclear speckles requires signals within the acidic, basic, and coiled-coil domains. CGBP associates with the nuclear matrix, and fragments of CGBP that fail to associate with the nuclear matrix fail to localize to nuclear speckles and exhibit reduced transcriptional activation activity. Mutated versions of CGBP that lack DNA binding activity exhibit a normal nuclear distribution, suggesting that CGBP accumulates at nuclear speckles as a result of protein/protein interactions. Importantly, the subcellular distribution of CGBP is identical to human trithorax, suggesting that these proteins may be components of a multimeric complex analogous to the histone-methylating Set1 complex of Saccharomyces cerevisiae that contains CGBP and trithorax homologues.
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Affiliation(s)
- Jeong-Heon Lee
- Herman B Wells Center for Pediatric Research, Section of Pediatric Hematology/Oncology, Department of Pediatrics and Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis 46202, USA
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Affiliation(s)
- Louise K Jones
- Cancer Research UK Children's Cancer Group, Department of Paediatric Haematology and Oncology, Royal London Hospital, London, UK
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Haviernik P, Festin SM, Opavsky R, Koller RP, Barr NI, Neil JC, Wolff L. Linkage on chromosome 10 of several murine retroviral integration loci associated with leukaemia. J Gen Virol 2002; 83:819-827. [PMID: 11907331 DOI: 10.1099/0022-1317-83-4-819] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Mml loci have been identified as provirus integration sites among a subset of monocytic tumours induced by murine leukaemia virus (MuLV) infection of BALB/c and DBA/2 mice. These myeloid leukaemias contain a retrovirus integrated on chromosome 10 in proximity to the c-myb locus; however, c-myb expression was not altered. Detailed physical mapping enabled placement of the retroviral integration sites approximately 25 kb (Mml1), approximately 51 kb (Mml2), and approximately 70 kb (Mml3) upstream of the c-myb locus. Furthermore, the Fti1 (fit-1) locus, a common integration site in feline leukaemia virus-induced T cell lymphomas, was mapped upstream of Mml3. Sequence analysis of Mml1, Mml2 and Mml3 loci (39.6, 16.4 and 5.9 kb, respectively) in conjunction with the BLAST (basic local alignment search tool) homology searches against the expressed sequence tag (EST) database and the use of gene/exon prediction programs revealed potential coding sequences that were not confirmed by Northern analysis or RT-PCR. The sequences between c-myb and Fti1, which were shown to include two potential scaffold/matrix attachment regions (S/MARs), are most likely regulatory in nature. An extended search for transcribed sequences far upstream of Mml3 revealed five genes, four of which were expressed in multiple tissues in mice. These genes could not be linked to tumour formation by the virus but their homologous sequences were found on human chromosome 6, thus allowing extension of the syntenic region on mouse chromosome 10 to approximately 250 kb.
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Affiliation(s)
- Peter Haviernik
- Leukemogenesis Section, Laboratory of Cellular Oncology, National Cancer Institute, NIH, Bethesda, MD 20892-4255, USA1
| | - Stephen M Festin
- Leukemogenesis Section, Laboratory of Cellular Oncology, National Cancer Institute, NIH, Bethesda, MD 20892-4255, USA1
| | - Rene Opavsky
- Leukemogenesis Section, Laboratory of Cellular Oncology, National Cancer Institute, NIH, Bethesda, MD 20892-4255, USA1
| | - Richard P Koller
- Leukemogenesis Section, Laboratory of Cellular Oncology, National Cancer Institute, NIH, Bethesda, MD 20892-4255, USA1
| | - Nighean I Barr
- Molecular Oncology Laboratory, University of Glasgow, Glasgow G61 1QH, UK2
| | - James C Neil
- Molecular Oncology Laboratory, University of Glasgow, Glasgow G61 1QH, UK2
| | - Linda Wolff
- Leukemogenesis Section, Laboratory of Cellular Oncology, National Cancer Institute, NIH, Bethesda, MD 20892-4255, USA1
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