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Noble TD, Sansam CG, Wittig KA, Majchrzycka B, Sansam CL. Cell Cycle-Dependent TICRR/TRESLIN and MTBP Chromatin Binding Mechanisms and Patterns. bioRxiv 2024:2024.02.02.578516. [PMID: 38370757 PMCID: PMC10871258 DOI: 10.1101/2024.02.02.578516] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/20/2024]
Abstract
The selection of replication origins is a defining characteristic of DNA replication in eukaryotes, yet its mechanism in humans has not been well-defined. In this study, we use Cut&Run to examine genomic binding locations for TICRR/TRESLIN and MTBP, the human orthologs for the yeast DNA replication initiation factors Sld3 and Sld7. We mapped TRESLIN and MTBP binding in HCT116 colorectal cancer cells using asynchronous and G1 synchronized populations. Our data show that TRESLIN and MTBP binding patterns are more defined in a G1 synchronized population compared to asynchronously cycling cells. We also examined whether TRESLIN and MTBP are dependent on one another for binding. Our data suggest MTBP is dependent on TRESLIN for proper association with chromatin during G1 but not S phase. Finally, we asked whether TRESLIN and MTBP binding to chromatin requires licensed origins. Using cell lines with a non-degradable inducible Geminin to inhibit licensing, we show TRESLIN and MTBP binding does not require loaded MCMs. Altogether, our Cut&Run data provides evidence for a chromatin binding mechanism of TRESLIN-MTBP during G1 that is dependent on TRESLIN and does not require interactions with licensed origins.
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Affiliation(s)
- Tyler D Noble
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104
- Cell Cycle and Cancer Biology Research Program, Oklahoma Medical Research Foundation, Oklahoma City, OK 73104
| | - Courtney G Sansam
- Cell Cycle and Cancer Biology Research Program, Oklahoma Medical Research Foundation, Oklahoma City, OK 73104
| | - Kimberlie A Wittig
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104
- Cell Cycle and Cancer Biology Research Program, Oklahoma Medical Research Foundation, Oklahoma City, OK 73104
| | - Blanka Majchrzycka
- Cell Cycle and Cancer Biology Research Program, Oklahoma Medical Research Foundation, Oklahoma City, OK 73104
| | - Christopher L Sansam
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104
- Cell Cycle and Cancer Biology Research Program, Oklahoma Medical Research Foundation, Oklahoma City, OK 73104
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Wittig KA, Sansam CG, Noble TD, Goins D, Sansam CL. The CRL4DTL E3 ligase induces degradation of the DNA replication initiation factor TICRR/TRESLIN specifically during S phase. Nucleic Acids Res 2021; 49:10507-10523. [PMID: 34534348 PMCID: PMC8501952 DOI: 10.1093/nar/gkab805] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2021] [Revised: 08/26/2021] [Accepted: 09/13/2021] [Indexed: 01/02/2023] Open
Abstract
A DNA replication program, which ensures that the genome is accurately and wholly replicated, is established during G1, before the onset of S phase. In G1, replication origins are licensed, and upon S phase entry, a subset of these will form active replisomes. Tight regulation of the number of active replisomes is crucial to prevent replication stress-induced DNA damage. TICRR/TRESLIN is essential for DNA replication initiation, and the level of TICRR and its phosphorylation determine the number of origins that initiate during S phase. However, the mechanisms regulating TICRR protein levels are unknown. Therefore, we set out to define the TICRR/TRESLIN protein dynamics throughout the cell cycle. Here, we show that TICRR levels are high during G1 and dramatically decrease as cells enter S phase and begin DNA replication. We show that degradation of TICRR occurs specifically during S phase and depends on ubiquitin ligases and proteasomal degradation. Using two targeted siRNA screens, we identify CRL4DTL as a cullin complex necessary for TICRR degradation. We propose that this mechanism moderates the level of TICRR protein available for replication initiation, ensuring the proper number of active origins as cells progress through S phase.
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Affiliation(s)
- Kimberlie A Wittig
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA.,Cell Cycle and Cancer Biology Research Program, Oklahoma Medical Research Foundation, Oklahoma City, OK 73104, USA
| | - Courtney G Sansam
- Cell Cycle and Cancer Biology Research Program, Oklahoma Medical Research Foundation, Oklahoma City, OK 73104, USA
| | - Tyler D Noble
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA.,Cell Cycle and Cancer Biology Research Program, Oklahoma Medical Research Foundation, Oklahoma City, OK 73104, USA
| | - Duane Goins
- Cell Cycle and Cancer Biology Research Program, Oklahoma Medical Research Foundation, Oklahoma City, OK 73104, USA
| | - Christopher L Sansam
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA.,Cell Cycle and Cancer Biology Research Program, Oklahoma Medical Research Foundation, Oklahoma City, OK 73104, USA
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Sansam CG, Pietrzak K, Majchrzycka B, Kerlin MA, Chen J, Rankin S, Sansam CL. A mechanism for epigenetic control of DNA replication. Genes Dev 2018; 32:224-229. [PMID: 29483155 DOI: 10.1101/gad.306464.117] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2017] [Accepted: 01/23/2018] [Indexed: 01/12/2023]
Abstract
DNA replication origins in hyperacetylated euchromatin fire preferentially during early S phase. However, how acetylation controls DNA replication timing is unknown. TICRR/TRESLIN is an essential protein required for the initiation of DNA replication. Here, we report that TICRR physically interacts with the acetyl-histone binding bromodomain (BRD) and extraterminal (BET) proteins BRD2 and BRD4. Abrogation of this interaction impairs TICRR binding to acetylated chromatin and disrupts normal S-phase progression. Our data reveal a novel function for BET proteins and establish the TICRR-BET interaction as a potential mechanism for epigenetic control of DNA replication.
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Affiliation(s)
- Courtney G Sansam
- Oklahoma Medical Research Foundation, Cell Cycle and Cancer Biology Research Program, Oklahoma City, Oklahoma 73104, USA
| | - Katarzyna Pietrzak
- Oklahoma Medical Research Foundation, Cell Cycle and Cancer Biology Research Program, Oklahoma City, Oklahoma 73104, USA
| | - Blanka Majchrzycka
- Oklahoma Medical Research Foundation, Cell Cycle and Cancer Biology Research Program, Oklahoma City, Oklahoma 73104, USA
| | - Maciej A Kerlin
- Oklahoma Medical Research Foundation, Cell Cycle and Cancer Biology Research Program, Oklahoma City, Oklahoma 73104, USA
| | - Jingrong Chen
- Oklahoma Medical Research Foundation, Cell Cycle and Cancer Biology Research Program, Oklahoma City, Oklahoma 73104, USA
| | - Susannah Rankin
- Oklahoma Medical Research Foundation, Cell Cycle and Cancer Biology Research Program, Oklahoma City, Oklahoma 73104, USA.,University of Oklahoma Health Sciences Center, Department of Cell Biology, Oklahoma City, Oklahoma 73104, USA
| | - Christopher L Sansam
- Oklahoma Medical Research Foundation, Cell Cycle and Cancer Biology Research Program, Oklahoma City, Oklahoma 73104, USA.,University of Oklahoma Health Sciences Center, Department of Cell Biology, Oklahoma City, Oklahoma 73104, USA
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Alomer RM, da Silva EML, Chen J, Piekarz KM, McDonald K, Sansam CG, Sansam CL, Rankin S. Esco1 and Esco2 regulate distinct cohesin functions during cell cycle progression. Proc Natl Acad Sci U S A 2017; 114:9906-9911. [PMID: 28847955 PMCID: PMC5604028 DOI: 10.1073/pnas.1708291114] [Citation(s) in RCA: 62] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Sister chromatids are tethered together by the cohesin complex from the time they are made until their separation at anaphase. The ability of cohesin to tether sister chromatids together depends on acetylation of its Smc3 subunit by members of the Eco1 family of cohesin acetyltransferases. Vertebrates express two orthologs of Eco1, called Esco1 and Esco2, both of which are capable of modifying Smc3, but their relative contributions to sister chromatid cohesion are unknown. We therefore set out to determine the precise contributions of Esco1 and Esco2 to cohesion in vertebrate cells. Here we show that cohesion establishment is critically dependent upon Esco2. Although most Smc3 acetylation is Esco1 dependent, inactivation of the ESCO1 gene has little effect on mitotic cohesion. The unique ability of Esco2 to promote cohesion is mediated by sequences in the N terminus of the protein. We propose that Esco1-dependent modification of Smc3 regulates almost exclusively the noncohesive activities of cohesin, such as DNA repair, transcriptional control, chromosome loop formation, and/or stabilization. Collectively, our data indicate that Esco1 and Esco2 contribute to distinct and separable activities of cohesin in vertebrate cells.
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Affiliation(s)
- Reem M Alomer
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104
| | - Eulália M L da Silva
- Program in Cell Cycle and Cancer Biology, Oklahoma Medical Research Foundation, Oklahoma City, OK 73104
| | - Jingrong Chen
- Program in Cell Cycle and Cancer Biology, Oklahoma Medical Research Foundation, Oklahoma City, OK 73104
| | - Katarzyna M Piekarz
- Program in Cell Cycle and Cancer Biology, Oklahoma Medical Research Foundation, Oklahoma City, OK 73104
| | - Katherine McDonald
- Program in Cell Cycle and Cancer Biology, Oklahoma Medical Research Foundation, Oklahoma City, OK 73104
| | - Courtney G Sansam
- Program in Cell Cycle and Cancer Biology, Oklahoma Medical Research Foundation, Oklahoma City, OK 73104
| | - Christopher L Sansam
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104
- Program in Cell Cycle and Cancer Biology, Oklahoma Medical Research Foundation, Oklahoma City, OK 73104
| | - Susannah Rankin
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104;
- Program in Cell Cycle and Cancer Biology, Oklahoma Medical Research Foundation, Oklahoma City, OK 73104
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Sansam CG, Goins D, Siefert JC, Clowdus EA, Sansam CL. Cyclin-dependent kinase regulates the length of S phase through TICRR/TRESLIN phosphorylation. Genes Dev 2015; 29:555-66. [PMID: 25737283 PMCID: PMC4358407 DOI: 10.1101/gad.246827.114] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2014] [Accepted: 01/23/2015] [Indexed: 12/22/2022]
Abstract
S-phase cyclin-dependent kinases (CDKs) stimulate replication initiation and accelerate progression through the replication timing program, but it is unknown which CDK substrates are responsible for these effects. CDK phosphorylation of the replication factor TICRR (TopBP1-interacting checkpoint and replication regulator)/TRESLIN is required for DNA replication. We show here that phosphorylated TICRR is limiting for S-phase progression. Overexpression of a TICRR mutant with phosphomimetic mutations at two key CDK-phosphorylated residues (TICRR(TESE)) stimulates DNA synthesis and shortens S phase by increasing replication initiation. This effect requires the TICRR region that is necessary for its interaction with MDM two-binding protein. Expression of TICRR(TESE) does not grossly alter the spatial organization of replication forks in the nucleus but does increase replication clusters and the number of replication forks within each cluster. In contrast to CDK hyperactivation, the acceleration of S-phase progression by TICRR(TESE) does not induce DNA damage. These results show that CDK can stimulate initiation and compress the replication timing program by phosphorylating a single protein, suggesting a simple mechanism by which S-phase length is controlled.
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Affiliation(s)
- Courtney G Sansam
- Cell Cycle and Cancer Biology Research Program, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma 73104, USA;
| | - Duane Goins
- Cell Cycle and Cancer Biology Research Program, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma 73104, USA
| | - Joseph C Siefert
- Cell Cycle and Cancer Biology Research Program, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma 73104, USA; Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104, USA
| | - Emily A Clowdus
- Cell Cycle and Cancer Biology Research Program, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma 73104, USA; Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104, USA
| | - Christopher L Sansam
- Cell Cycle and Cancer Biology Research Program, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma 73104, USA; Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104, USA
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McKenna ES, Tamayo P, Cho YJ, Tillman EJ, Mora-Blanco EL, Sansam CG, Koellhoffer EC, Pomeroy SL, Roberts CWM. Epigenetic inactivation of the tumor suppressor BIN1 drives proliferation of SNF5-deficient tumors. Cell Cycle 2012; 11:1956-65. [PMID: 22544318 DOI: 10.4161/cc.20280] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Emerging evidence demonstrates that subunits of the SWI/SNF chromatin remodeling complex are specifically mutated at high frequency in a variety of human cancer types. SNF5 (SMARCB1/INI1/BAF47), a core subunit of the SWI/SNF complex, is inactivated in the vast majority of rhabdoid tumors (RT), an aggressive type of pediatric cancer. SNF5-deficient cancers are diploid and genomically stable, suggesting that epigenetically based changes in transcription are key drivers of tumor formation caused by SNF5 loss. However, there is limited understanding of the target genes that drive cancer formation following SNF5 loss. Here we performed comparative expression analyses upon three independent SNF5-deficient cancer data sets from both human and mouse and identify downregulation of the BIN1 tumor suppressor as a conserved event in primary SNF5-deficient cancers. We show that SNF5 recruits the SWI/SNF complex to the BIN1 promoter, and that the marked reduction of BIN1 expression in RT correlates with decreased SWI/SNF occupancy. Functionally, we demonstrate that re-expression of BIN1 specifically compromises the proliferation of SNF5-deficient RT cell lines. Identification of BIN1 as a SNF5 target gene reveals a novel tumor suppressive regulatory mechanism whose disruption can drive cancer formation.
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Affiliation(s)
- Elizabeth S McKenna
- Department of Pediatric Oncology, Dana-Farber Cancer Institute, Boston, MA USA
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Wang X, Werneck MBF, Wilson BG, Kim HJ, Kluk MJ, Thom CS, Wischhusen JW, Evans JA, Jesneck JL, Nguyen P, Sansam CG, Cantor H, Roberts CWM. TCR-dependent transformation of mature memory phenotype T cells in mice. J Clin Invest 2011; 121:3834-45. [PMID: 21926465 PMCID: PMC3195451 DOI: 10.1172/jci37210] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2011] [Accepted: 08/03/2011] [Indexed: 01/21/2023] Open
Abstract
A fundamental goal in cancer research is the identification of the cell types and signaling pathways capable of initiating and sustaining tumor growth, as this has the potential to reveal therapeutic targets. Stem and progenitor cells have been implicated in the genesis of select lymphoid malignancies. However, the identity of the cells in which mature lymphoid neoplasms are initiated remains unclear. Here, we investigate the origin of peripheral T cell lymphomas using mice in which Snf5, a chromatin remodelling-complex subunit with tumor suppressor activity, could be conditionally inactivated in developing T cells. In this model of mature peripheral T cell lymphomas, the cell of origin was a mature CD44hiCD122loCD8⁺ T cell that resembled a subset of memory cells that has capacity for self-renewal and robust expansion, features shared with stem cells. Further analysis showed that Snf5 loss led to activation of a Myc-driven signaling network and stem cell transcriptional program. Finally, lymphomagenesis and lymphoma proliferation depended upon TCR signaling, establishing what we believe to be a new paradigm for lymphoid malignancy growth. These findings suggest that the self-renewal and robust proliferative capacities of memory T cells are associated with vulnerability to oncogenic transformation. Our findings further suggest that agents that impinge upon TCR signaling may represent an effective therapeutic modality for this class of lethal human cancers.
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Affiliation(s)
- Xi Wang
- Department of Pediatric Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts 02115, USA
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McKenna ES, Tamayo P, Cho YJ, Mora-Blanco EL, Sansam CG, Tillman EJ, Koellhoffer EC, Pomeroy SL, Roberts CWM. Abstract 66: Epigenetic inactivation of the tumor suppressor BIN1 drives proliferation of SNF5-deficient tumors. Cancer Res 2011. [DOI: 10.1158/1538-7445.am2011-66] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Abstract
SNF5 (SMARCB1/INI1/BAF47), a core subunit of SWI/SNF chromatin remodeling complexes, is a potent tumor suppressor that is specifically inactivated in a variety of aggressive pediatric cancers. We have recently demonstrated that SNF5 acts as a tumor suppressor not genetically via maintenance of genome integrity, but epigenetically via transcriptional regulation. However, few of the target genes essential for oncogenesis following SNF5 loss have been identified. Here, we demonstrate that aberrant epigenetic silencing of the tumor suppressor gene BIN1 is a conserved event in SNF5-deficient cancers and contributes to tumorigenesis. Comparative genomewide expression analysis reveals that BIN1 expression is strongly downregulated in SNF5-deficient malignant rhabdoid tumors (MRT) relative to other human tumors, and we also observe decreased Bin1 expression in murine Snf5-deficient lymphomas. The underlying mechanism is epigenetic silencing as reintroduction of SNF5 into deficient tumor cell lines results in increased SWI/SNF recruitment to the BIN1 promoter and increased BIN1 expression. Furthermore, expression of BIN1 specifically compromises the proliferation of SNF5-deficient MRT cell lines. BIN1 encodes a family of alternatively spliced adaptor proteins that have been implicated in cellular differentiation, tumor suppression, and immune escape of transformed cells, but its regulation has not been well characterized. Identification of BIN1 as a key SNF5 target reveals a novel mechanism by which epigenetically based changes can drive cancer formation.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 66. doi:10.1158/1538-7445.AM2011-66
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Affiliation(s)
- Elizabeth S. McKenna
- 1Department of Pediatric Oncology, Dana-Farber Cancer Institute, Division of Hematology/Oncology, Children's Hospital Boston, Department of Pediatrics, Harvard Medical School, Boston, MA
| | - Pablo Tamayo
- 2The Eli and Edythe L. Broad Institute of Massachusetts Institute of Technology and Harvard University, Cambridge, MA
| | - Yoon-Jae Cho
- 3Department of Neurology, Children's Hospital Boston, Boston, MA
| | - E. Lorena Mora-Blanco
- 1Department of Pediatric Oncology, Dana-Farber Cancer Institute, Division of Hematology/Oncology, Children's Hospital Boston, Department of Pediatrics, Harvard Medical School, Boston, MA
| | - Courtney G. Sansam
- 1Department of Pediatric Oncology, Dana-Farber Cancer Institute, Division of Hematology/Oncology, Children's Hospital Boston, Department of Pediatrics, Harvard Medical School, Boston, MA
| | - Erik J. Tillman
- 1Department of Pediatric Oncology, Dana-Farber Cancer Institute, Division of Hematology/Oncology, Children's Hospital Boston, Department of Pediatrics, Harvard Medical School, Boston, MA
| | - Edward C. Koellhoffer
- 1Department of Pediatric Oncology, Dana-Farber Cancer Institute, Division of Hematology/Oncology, Children's Hospital Boston, Department of Pediatrics, Harvard Medical School, Boston, MA
| | - Scott L. Pomeroy
- 3Department of Neurology, Children's Hospital Boston, Boston, MA
| | - Charles W. M. Roberts
- 1Department of Pediatric Oncology, Dana-Farber Cancer Institute, Division of Hematology/Oncology, Children's Hospital Boston, Department of Pediatrics, Harvard Medical School, Boston, MA
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Jagani Z, Mora-Blanco EL, Sansam CG, McKenna ES, Wilson B, Chen D, Klekota J, Tamayo P, Nguyen PTL, Tolstorukov M, Park PJ, Cho YJ, Hsiao K, Buonamici S, Pomeroy SL, Mesirov JP, Ruffner H, Bouwmeester T, Luchansky SJ, Murtie J, Kelleher JF, Warmuth M, Sellers WR, Roberts CWM, Dorsch M. Loss of the tumor suppressor Snf5 leads to aberrant activation of the Hedgehog-Gli pathway. Nat Med 2010; 16:1429-33. [PMID: 21076395 DOI: 10.1038/nm.2251] [Citation(s) in RCA: 187] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2010] [Accepted: 09/30/2010] [Indexed: 01/18/2023]
Abstract
Aberrant activation of the Hedgehog (Hh) pathway can drive tumorigenesis. To investigate the mechanism by which glioma-associated oncogene family zinc finger-1 (GLI1), a crucial effector of Hh signaling, regulates Hh pathway activation, we searched for GLI1-interacting proteins. We report that the chromatin remodeling protein SNF5 (encoded by SMARCB1, hereafter called SNF5), which is inactivated in human malignant rhabdoid tumors (MRTs), interacts with GLI1. We show that Snf5 localizes to Gli1-regulated promoters and that loss of Snf5 leads to activation of the Hh-Gli pathway. Conversely, re-expression of SNF5 in MRT cells represses GLI1. Consistent with this, we show the presence of a Hh-Gli-activated gene expression profile in primary MRTs and show that GLI1 drives the growth of SNF5-deficient MRT cells in vitro and in vivo. Therefore, our studies reveal that SNF5 is a key mediator of Hh signaling and that aberrant activation of GLI1 is a previously undescribed targetable mechanism contributing to the growth of MRT cells.
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Affiliation(s)
- Zainab Jagani
- Novartis Institutes for BioMedical Research, Cambridge, Massachusetts, USA
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Wang X, Sansam CG, Thom CS, Metzger D, Evans JA, Nguyen PTL, Roberts CWM. Oncogenesis caused by loss of the SNF5 tumor suppressor is dependent on activity of BRG1, the ATPase of the SWI/SNF chromatin remodeling complex. Cancer Res 2009; 69:8094-101. [PMID: 19789351 DOI: 10.1158/0008-5472.can-09-0733] [Citation(s) in RCA: 120] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Alterations in chromatin play an important role in oncogenic transformation, although the underlying mechanisms are often poorly understood. The SWI/SNF complex contributes to epigenetic regulation by using the energy of ATP hydrolysis to remodel chromatin and thus regulate transcription of target genes. SNF5, a core subunit of the SWI/SNF complex, is a potent tumor suppressor that is specifically inactivated in several types of human cancer. However, the mechanism by which SNF5 mutation leads to cancer and the role of SNF5 within the SWI/SNF complex remain largely unknown. It has been hypothesized that oncogenesis in the absence of SNF5 occurs due to a loss of function of the SWI/SNF complex. Here, we show, however, distinct effects for inactivation of Snf5 and the ATPase subunit Brg1 in primary cells. Further, using both human cell lines and mouse models, we show that cancer formation in the absence of SNF5 does not result from SWI/SNF inactivation but rather that oncogenesis is dependent on continued presence of BRG1. Collectively, our results show that cancer formation in the absence of SNF5 is dependent on the activity of the residual BRG1-containing SWI/SNF complex. These findings suggest that, much like the concept of oncogene addiction, targeted inhibition of SWI/SNF ATPase activity may be an effective therapeutic approach for aggressive SNF5-deficient human tumors.
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Affiliation(s)
- Xi Wang
- Department of Pediatric Oncology, Dana-Farber Cancer Institute, Children's Hospital Boston, Boston, Massachusetts 02115, USA
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11
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Bourgo RJ, Siddiqui H, Fox S, Solomon D, Sansam CG, Yaniv M, Muchardt C, Metzger D, Chambon P, Roberts CWM, Knudsen ES. SWI/SNF deficiency results in aberrant chromatin organization, mitotic failure, and diminished proliferative capacity. Mol Biol Cell 2009; 20:3192-9. [PMID: 19458193 DOI: 10.1091/mbc.e08-12-1224] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Switch (SWI)/sucrose nonfermentable (SNF) is an evolutionarily conserved complex with ATPase function, capable of regulating nucleosome position to alter transcriptional programs within the cell. It is known that the SWI/SNF complex is responsible for regulation of many genes involved in cell cycle control and proliferation, and it has recently been implicated in cancer development. The ATPase action of SWI/SNF is conferred through either the brahma-related gene 1 (Brg1) or brahma (Brm) subunit of the complex, and it is of central importance to the modification of nucleosome position. In this study, the role of the Brg1 and Brm subunits were examined as they relate to chromatin structure and organization. Deletion of the Brg1 ATPase results in dissolution of pericentromeric heterochromatin domains and a redistribution of histone modifications associated with these structures. This effect was highly specific to Brg1 and is not reproduced by the loss of Brm or SNF5/BAF47/INI1. Brg1 deficiency is associated with the appearance of micronuclei and aberrant mitoses that are a by-product of dissociated chromatin structure. Thus, Brg1 plays a critical role in maintaining chromatin structural integrity.
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Affiliation(s)
- Ryan J Bourgo
- *Department of Cancer Biology, Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, PA 19107, USA.
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Janumyan Y, Cui Q, Yan L, Sansam CG, Valentin M, Yang E. G0 function of BCL2 and BCL-xL requires BAX, BAK, and p27 phosphorylation by Mirk, revealing a novel role of BAX and BAK in quiescence regulation. J Biol Chem 2008; 283:34108-20. [PMID: 18818203 PMCID: PMC2590681 DOI: 10.1074/jbc.m806294200] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2008] [Revised: 09/25/2008] [Indexed: 11/06/2022] Open
Abstract
BCL2 and BCL-x(L) facilitate G(0) quiescence by decreasing RNA content and cell size and up-regulating p27 protein, but the precise mechanism is not understood. We investigated the relationship between cell cycle regulation and the anti-apoptosis function of BCL2 and BCL-x(L). Neither caspase inhibition nor abrogation of mitochondria-dependent apoptosis by BAX and BAK deletion fully recapitulated the G(0) effects of BCL2 or BCL-x(L), suggesting that mechanisms in addition to anti-apoptosis are involved in the cell cycle arrest function of BCL2 or BCL-x(L). We found that BCL2 and BCL-x(L) expression in bax(-/-) bak(-/-) cells did not confer cell cycle effects, consistent with the G(0) function of BCL2 and BCL-x(L) being mediated through BAX or BAK. Stabilization of p27 in G(0) in BCL2 or BCL-x(L) cells was due to phosphorylation of p27 at Ser(10) by the kinase Mirk. In bax(-/-) bak(-/-) cells, total p27 and p27 phosphorylated at Ser(10) were elevated. Re-expression of BAX in bax(-/-) bak(-/-) cells and silencing of BAX and BAK in wild type cells confirmed that endogenous BAX and BAK modulated p27. These data revealed a novel role for BAX and BAK in the regulation of G(0) quiescence.
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Affiliation(s)
- Yelena Janumyan
- Department of Pediatrics, Vanderbilt-Ingram Cancer Center, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, USA
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Sansam CG, Roberts CWM. Epigenetics and cancer: altered chromatin remodeling via Snf5 loss leads to aberrant cell cycle regulation. Cell Cycle 2006; 5:621-4. [PMID: 16582616 DOI: 10.4161/cc.5.6.2579] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The term 'epigenetics' refers to heritable changes in gene function that occur in the absence of any change in DNA sequence. Perturbations of epigenetic gene regulation may play a critical role in the genesis of most, if not all, cancers. These alterations include changes in covalent modifications of DNA and histones as well as non covalent changes in nucleosome positioning. Covalent epigenetic modifications have been the main focus of cancer investigation, perhaps because they are more readily assayed and understood than non covalent modifications. Recently, evidence has emerged demonstrating that perturbation of complexes that remodel the structure of chromatin by mobilizing nucleosomes may have a key role in tumor suppression and oncogenic transformation. For example, Snf5 (Ini1/Baf47/Smarcb1), a core component of the Swi/Snf ATPase chromatin remodeling complex, is a potent tumor suppressor that is specifically inactivated in lethal childhood cancers. Notably, these cancers may serve as a paradigm for epigenetic cancers as, despite their extremely aggressive nature, the majority have an entirely normal karyotype with only microdeletions at the Snf5 locus. Recent investigations have shed light upon the mechanistic basis of Snf5 function by demonstrating that Snf5 and the Swi/Snf complex regulate the cell cycle and cooperate with p53 to prevent oncogenic transformation.
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Affiliation(s)
- Courtney G Sansam
- Department of Pediatric Oncology, Division of Hematology/Oncology, Children's Hospital Boston, Harvard Medical School, Dana-Farber Cancer Institute, Boston, Massachusetts 02115, USA
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Isakoff MS, Sansam CG, Tamayo P, Subramanian A, Evans JA, Fillmore CM, Wang X, Biegel JA, Pomeroy SL, Mesirov JP, Roberts CWM. Inactivation of the Snf5 tumor suppressor stimulates cell cycle progression and cooperates with p53 loss in oncogenic transformation. Proc Natl Acad Sci U S A 2005; 102:17745-50. [PMID: 16301525 PMCID: PMC1308926 DOI: 10.1073/pnas.0509014102] [Citation(s) in RCA: 154] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Snf5 (Ini1/Baf47/Smarcb1), a core member of the Swi/Snf chromatin remodeling complex, is a potent tumor suppressor whose mechanism of action is largely unknown. Biallelic loss of Snf5 leads to the onset of aggressive cancers in both humans and mice. We have developed an innovative and widely applicable analytical technique for cross-species validation of cancer models and show that the gene expression profiles of our Snf5 murine models closely resemble those of human Snf5-deficient rhabdoid tumors. We exploit this system to produce what we believe to be the first report documenting the effects on gene expression of inactivating a Swi/Snf subunit in normal mammalian cells and to identify the transcriptional pathways regulated by Snf5. We demonstrate that the tumor suppressor activity of Snf5 depends on its regulation of cell cycle progression; Snf5 inactivation leads to aberrant up-regulation of E2F targets and increased levels of p53 that are accompanied by apoptosis, polyploidy, and growth arrest. Further, conditional mouse models demonstrate that inactivation of p16Ink4a or Rb (retinoblastoma) does not accelerate tumor formation in Snf5 conditional mice, whereas mutation of p53 leads to a dramatic acceleration of tumor formation.
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Affiliation(s)
- Michael S Isakoff
- Department of Pediatric Oncology, Dana-Farber Cancer Institute, Boston, MA 02115, USA
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Janumyan YM, Sansam CG, Chattopadhyay A, Cheng N, Soucie EL, Penn LZ, Andrews D, Knudson CM, Yang E. Bcl-xL/Bcl-2 coordinately regulates apoptosis, cell cycle arrest and cell cycle entry. EMBO J 2004; 22:5459-70. [PMID: 14532118 PMCID: PMC213787 DOI: 10.1093/emboj/cdg533] [Citation(s) in RCA: 156] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Bcl-x(L) and Bcl-2 inhibit both apoptosis and proliferation. In investigating the relationship between these two functions of Bcl-x(L) and Bcl-2, an analysis of 24 Bcl-x(L) and Bcl-2 mutant alleles, including substitutions at residue Y28 previously reported to selectively abolish the cell cycle activity, showed that cell cycle delay and anti-apoptosis co-segregated in all cases. In determining whether Bcl-2 and Bcl-x(L) act in G(0) or G(1), forward scatter and pyronin Y fluorescence measurements indicated that Bcl-2 and Bcl-x(L) cells arrested more effectively in G(0) than controls, and were delayed in G(0)-G(1) transition. The cell cycle effects of Bcl-2 and Bcl-x(L) were reversed by Bad, a molecule that counters the survival function of Bcl-2 and Bcl-x(L). When control and Bcl-x(L) cells of equivalent size and pyronin Y fluorescence were compared, the kinetics of cell cycle entry were similar, demonstrating that the ability of Bcl-x(L) and Bcl-2 cells to enhance G(0) arrest contributes significantly to cell cycle delay. Our data suggest that cell cycle effects and increased survival both result from intrinsic functions of Bcl-2 and Bcl-x(L).
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Affiliation(s)
- Yelena M Janumyan
- Department of Cancer Biology, Vanderbilt-Ingram Cancer Center, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
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Irvin BJ, Wood LD, Wang L, Fenrick R, Sansam CG, Packham G, Kinch M, Yang E, Hiebert SW. TEL, a putative tumor suppressor, induces apoptosis and represses transcription of Bcl-XL. J Biol Chem 2003; 278:46378-86. [PMID: 12960174 DOI: 10.1074/jbc.m305189200] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The ETS family transcriptional repressor TEL is frequently disrupted by chromosomal translocations, including the t(12;21) in which the second allele of TEL is deleted in up to 90% of the cases. Consistent with its role as a putative tumor suppressor, TEL expression inhibits colony formation by Ras-transformed NIH 3T3 cells and hinders proliferation of a variety of cell types. Although we observed no alteration in the cell cycle of TEL-expressing cells, we did find a marked increase in apoptosis of serum-starved TEL-expressing NIH 3T3 cells. This decrease in cell survival required the DNA binding domain of TEL, suggesting that TEL repressed an anti-apoptotic gene. These observations prompted us to search for genes regulated by ETS family proteins that regulate apoptosis. The anti-apoptotic molecule Bcl-XL contains multiple ets-factor binding sites within its promoters, and TEL repressed a Bcl-XL promoter-linked reporter gene. Moreover, the enforced expression of TEL decreased the endogenous expression of both Bcl-XL mRNA and protein. TEL-mediated repression of Bcl-XL likely affects cell survival via regulation of the apoptotic pathway.
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Affiliation(s)
- Brenda J Irvin
- Department of Biochemistry, Vanderbilt-Ingram Cancer Center, Vanderbilt University School of Medicine, Preston Research Building, 23rd and Pierce, Nashville, TN 37232, USA
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