1
|
de Groot AP, de Haan G. How CBX proteins regulate normal and leukemic blood cells. FEBS Lett 2024. [PMID: 38426219 DOI: 10.1002/1873-3468.14839] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2023] [Revised: 01/26/2024] [Accepted: 02/09/2024] [Indexed: 03/02/2024]
Abstract
Hematopoietic stem cell (HSC) fate decisions are dictated by epigenetic landscapes. The Polycomb Repressive Complex 1 (PRC1) represses genes that induce differentiation, thereby maintaining HSC self-renewal. Depending on which chromobox (CBX) protein (CBX2, CBX4, CBX6, CBX7, or CBX8) is part of the PRC1 complex, HSC fate decisions differ. Here, we review how this occurs. We describe how CBX proteins dictate age-related changes in HSCs and stimulate oncogenic HSC fate decisions, either as canonical PRC1 members or by alternative interactions, including non-epigenetic regulation. CBX2, CBX7, and CBX8 enhance leukemia progression. To target, reprogram, and kill leukemic cells, we suggest and describe multiple therapeutic strategies to interfere with the epigenetic functions of oncogenic CBX proteins. Future studies should clarify to what extent the non-epigenetic function of cytoplasmic CBX proteins is important for normal, aged, and leukemic blood cells.
Collapse
Affiliation(s)
- Anne P de Groot
- European Research Institute for Biology of Ageing (ERIBA), University Medical Center Groningen (UMCG), The Netherlands
- Sanquin Research, Landsteiner Laboratory, Sanquin Blood Supply, Amsterdam, The Netherlands
| | - Gerald de Haan
- European Research Institute for Biology of Ageing (ERIBA), University Medical Center Groningen (UMCG), The Netherlands
- Sanquin Research, Landsteiner Laboratory, Sanquin Blood Supply, Amsterdam, The Netherlands
- Department of Hematology, Amsterdam UMC, University of Amsterdam, The Netherlands
| |
Collapse
|
2
|
Kabra A, Bushweller J. The Intrinsically Disordered Proteins MLLT3 (AF9) and MLLT1 (ENL) - Multimodal Transcriptional Switches With Roles in Normal Hematopoiesis, MLL Fusion Leukemia, and Kidney Cancer. J Mol Biol 2022; 434:167117. [PMID: 34174329 PMCID: PMC8695629 DOI: 10.1016/j.jmb.2021.167117] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [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] [Received: 05/07/2021] [Revised: 06/17/2021] [Accepted: 06/17/2021] [Indexed: 01/17/2023]
Abstract
AF9 (MLLT3) and ENL (MLLT1) are members of the YEATS family (named after the five proteins first shown to contain this domain: Yaf9, ENL, AF9, Taf14, Sas5) defined by the presence of a YEATS domain. The YEATS domain is an epigenetic reader that binds to acetylated and crotonylated lysines, unlike the bromodomain which can only bind to acetylated lysines. All members of this family have been shown to be components of various complexes with roles in chromatin remodeling, histone modification, histone variant deposition, and transcriptional regulation. MLLT3 is a critical regulator of hematopoiesis with a role in maintaining the hematopoietic stem or progenitor cell (HSPC) population. Approximately 10% of acute myeloid leukemia (AML) and acute lymphocytic leukemia (ALL) patients harbor a translocation involving MLL (mixed lineage leukemia). In the context of MLL fusion patients with AML and ALL, MLL-AF9 and MLL-ENL fusions are observed in 34 and 31% of the patients, respectively. The intrinsically disordered C-terminal domain of MLLT3 (AHD, ANC1 homology domain) undergoes coupled binding and folding upon interaction with partner proteins AF4, DOT1L, BCOR, and CBX8. Backbone dynamics studies of the complexes suggest a role for dynamics in function. Inhibitors of the interaction of the intrinsically disordered AHD with partner proteins have been described, highlighting the feasibility of targeting intrinsically disordered regions. MLLT1 undergoes phase separation to enhance recruitment of the super elongation complex (SEC) and drive transcription. Mutations in MLLT1 observed in Wilms tumor patients enhance phase separation and transcription to drive an aberrant gene expression program.
Collapse
Affiliation(s)
- Ashish Kabra
- Dept. of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA 22903, United States
| | - John Bushweller
- Dept. of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA 22903, United States; Dept. of Chemistry, University of Virginia, Charlottesville, VA 22904, United States.
| |
Collapse
|
3
|
Schmidt CR, Achille NJ, Kuntimaddi A, Boulton AM, Leach BI, Zhang S, Zeleznik-Le NJ, Bushweller JH. BCOR Binding to MLL-AF9 Is Essential for Leukemia via Altered EYA1, SIX, and MYC Activity. Blood Cancer Discov 2020; 1:162-177. [PMID: 32954361 DOI: 10.1158/2643-3230.bcd-20-0036] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [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: 12/31/2022] Open
Abstract
MLL is a target of chromosomal translocations in acute leukemias with poor prognosis. The common MLL fusion partner AF9 (MLLT3) can directly bind to AF4, DOT1L, BCOR, and CBX8. To delineate the relevance of BCOR and CBX8 binding to MLL-AF9 for leukemogenesis, here we determine protein structures of AF9 complexes with CBX8 and BCOR, and show that binding of all four partners to AF9 is mutually exclusive. Using the structural analyses, we identify point mutations that selectively disrupt AF9 interactions with BCOR and CBX8. In bone marrow stem/progenitor cells expressing point mutant CBX8 or point mutant MLL-AF9, we show that disruption of direct CBX8/MLL-AF9 binding does not impact in vitro cell proliferation, whereas loss of direct BCOR/MLL-AF9 binding causes partial differentiation and increased proliferation. Strikingly, loss of MLL-AF9/BCOR binding abrogated its leukemogenic potential in a mouse model. The MLL-AF9 mutant deficient for BCOR binding reduces the expression of the EYA1 phosphatase and the protein level of c-Myc. Reduction in BCOR binding to MLL-AF9 alters a MYC-driven gene expression program, as well as altering expression of SIX-regulated genes, likely contributing to the observed reduction in the leukemia-initiating cell population.
Collapse
Affiliation(s)
- Charles R Schmidt
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, Virginia
| | - Nicholas J Achille
- Department of Cancer Biology, Loyola University Chicago, Maywood, Illinois
| | - Aravinda Kuntimaddi
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, Virginia
| | - Adam M Boulton
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, Virginia
| | - Benjamin I Leach
- Department of Cancer Biology, Loyola University Chicago, Maywood, Illinois
| | - Shubin Zhang
- Department of Cancer Biology, Loyola University Chicago, Maywood, Illinois
| | - Nancy J Zeleznik-Le
- Department of Cancer Biology, Loyola University Chicago, Maywood, Illinois.
- Department of Medicine, Loyola University Chicago, Maywood, Illinois
| | - John H Bushweller
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, Virginia.
| |
Collapse
|
4
|
Abstract
Mutated or dysregulated transcription factors represent a unique class of drug targets that mediate aberrant gene expression, including blockade of differentiation and cell death gene expression programmes, hallmark properties of cancers. Transcription factor activity is altered in numerous cancer types via various direct mechanisms including chromosomal translocations, gene amplification or deletion, point mutations and alteration of expression, as well as indirectly through non-coding DNA mutations that affect transcription factor binding. Multiple approaches to target transcription factor activity have been demonstrated, preclinically and, in some cases, clinically, including inhibition of transcription factor-cofactor protein-protein interactions, inhibition of transcription factor-DNA binding and modulation of levels of transcription factor activity by altering levels of ubiquitylation and subsequent proteasome degradation or by inhibition of regulators of transcription factor expression. In addition, several new approaches to targeting transcription factors have recently emerged including modulation of auto-inhibition, proteolysis targeting chimaeras (PROTACs), use of cysteine reactive inhibitors, targeting intrinsically disordered regions of transcription factors and combinations of transcription factor inhibitors with kinase inhibitors to block the development of resistance. These innovations in drug development hold great promise to yield agents with unique properties that are likely to impact future cancer treatment.
Collapse
Affiliation(s)
- John H Bushweller
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA, USA.
- Department of Chemistry, University of Virginia, Charlottesville, VA, USA.
| |
Collapse
|
5
|
Kuntimaddi A, Achille NJ, Thorpe J, Lokken AA, Singh R, Hemenway CS, Adli M, Zeleznik-Le NJ, Bushweller JH. Degree of recruitment of DOT1L to MLL-AF9 defines level of H3K79 Di- and tri-methylation on target genes and transformation potential. Cell Rep 2015; 11:808-20. [PMID: 25921540 DOI: 10.1016/j.celrep.2015.04.004] [Citation(s) in RCA: 81] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2014] [Revised: 02/18/2015] [Accepted: 03/30/2015] [Indexed: 12/16/2022] Open
Abstract
The MLL gene is a common target of chromosomal translocations found in human leukemia. MLL-fusion leukemia has a consistently poor outcome. One of the most common translocation partners is AF9 (MLLT3). MLL-AF9 recruits DOT1L, a histone 3 lysine 79 methyltransferase (H3K79me1/me2/me3), leading to aberrant gene transcription. We show that DOT1L has three AF9 binding sites and present the nuclear magnetic resonance (NMR) solution structure of a DOT1L-AF9 complex. We generate structure-guided point mutations and find that they have graded effects on recruitment of DOT1L to MLL-AF9. Chromatin immunoprecipitation sequencing (ChIP-seq) analyses of H3K79me2 and H3K79me3 show that graded reduction of the DOT1L interaction with MLL-AF9 results in differential loss of H3K79me2 and me3 at MLL-AF9 target genes. Furthermore, the degree of DOT1L recruitment is linked to the level of MLL-AF9 hematopoietic transformation.
Collapse
Affiliation(s)
- Aravinda Kuntimaddi
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA 22908, USA
| | - Nicholas J Achille
- Oncology Institute, Department of Medicine, Loyola University Chicago, Maywood, IL 60153, USA
| | - Jeremy Thorpe
- Department of Biochemistry and Molecular Genetics, University of Virginia, Charlottesville, VA 22908, USA
| | - Alyson A Lokken
- Oncology Institute, Department of Medicine, Loyola University Chicago, Maywood, IL 60153, USA
| | - Ritambhara Singh
- Department of Biochemistry and Molecular Genetics, University of Virginia, Charlottesville, VA 22908, USA
| | - Charles S Hemenway
- Oncology Institute, Department of Pediatrics, Loyola University Chicago, Maywood, IL 60153, USA
| | - Mazhar Adli
- Department of Biochemistry and Molecular Genetics, University of Virginia, Charlottesville, VA 22908, USA
| | - Nancy J Zeleznik-Le
- Oncology Institute, Department of Medicine, Loyola University Chicago, Maywood, IL 60153, USA.
| | - John H Bushweller
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA 22908, USA.
| |
Collapse
|