PLZF-RARα Utilizes the Histone Methyl Transferase G9a/GLP and the Histone Demethylase LSD1 to Repress RARα Target Genes and Block Myeloid Differentiation

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 198-198
Author(s):  
Itsaso Hormaeche ◽  
Kim L. Rice ◽  
Arthur Zelent ◽  
Melanie J. McConnell ◽  
Jonathan D. Licht
Keyword(s):  
Fusion Protein ◽  
Transcriptional Repression ◽  
Histone Deacetylases ◽  
Target Genes ◽  
Myeloid Cell ◽  
Gene Repression ◽  
Methyl Transferase ◽  
Histone 3 ◽  
Histone Methyl Transferase

Abstract As a result of the t(11;17) translocation in retinoic acid resistant subtype of acute promyelocytic leukemia (APL), the transcriptional repression domains of the Promyelocytic Leukemia Zinc Finger protein (PLZF) are fused to the ligand binding and DNA binding domains of the Retinoic Acid Receptor α (RARα). The expression of PLZF-RARα as well as the reciprocal RARα-PLZF protein both appear to contribute to leukemogenesis. While the mode of action of PML-RARα has been studied in detail, less is known about transcriptional repression mediated by PLZF-RARα. We and others previously showed an important role of histone deacetylases in PLZF and PLZF-RARα mediated gene repression. We now find that expression of PLZF-RARα also modulates gene expression through changes in the state of histone methylation at target promoters. PLZF-RARα co-precipitated in vivo with endogenous G9a, a histone methyl transferase responsible for the mono and di-methylation of euchromatic histone 3 lysine tail residue 9 (H3K9me1/2), a covalent modification associated with gene repression. Deletion analysis of the PLZF-RARα fusion protein showed that the BTB/POZ domain of PLZF fused to RARα was sufficient to mediate this interaction. PLZF-RARα also bound in vivo to LSD1, a histone demethylase that removes methyl groups from mono or di-methylated Histone 3 lysine 4 (H3K4me1/2), a change generally associated with gene repression. As with G9a the BTB/POZ domain of PLZF was implicated in binding to LSD1. Co-precipitation experiments showed a robust interaction between PLZF-RARα and G9a and LSD1 while RARα, PML-RARα and NPM-RARα bound much more weakly, suggesting that the interaction with these histone modifying enzymes may be a mechanism relatively specific to t(11;17)-associated APL. To identify genes modulated by PLZF-RARα and determine how PLZF-RARα affects the chromatin of such genes we induced expression of PLZF-RARα in a U937 tetracycline-regulated system. PLZF-RARα directly repressed known RARα target genes such as NFE2, PRAM1 and C/EBPε. As a result of PLZF-RARα expression, U937T cells were blocked in differentiation characterized by decreased expression of the myeloid cell surface markers CD11b, CD14 and CD33. Chromatin immunoprecipitation experiments in this cell line showed that PLZF-RARα expression was associated with an increase in H3K9me1/me2 at the NFE2, PRAM1 and C/EBPε promoters. Knockdown of endogenous G9a by shRNA transduction reversed transcriptional repression mediated by the fusion protein on all three promoters. Both results are consistent with the presence of G9a in PLZF-RARα transcriptional complex. By contrast, the H3K4 methylation changes in response to PLZF-RARα were promoter specific and complex: while NFE2 exhibited a decrease in H3K4me1/2, consistent with the recruitment of LSD1 and demethylation, PRAM1 and C/EBPε showed an increase in these two modifications. Inhibition of LSD1 by tranylcypromine treatment as well as knockdown of LSD1 by shRNA only reverted PLZF-RARα repression of NFE2. PLZF-RARα recruitment to all three genes was associated with a decrease in H3K4trimethylation, a modification only accomplished by jumanji-class histone demethylases. Consistent with the biochemical information, knockdown of G9a or its heterodimeric partner GLP, showed a strong biological phenotype, reverting the block in myeloid differentiation caused by PLZF-RARα as measured by the expression of the myeloid cell surface markers CD11b and CD14. Depletion of LSD1 only modestly interfered with the differentiation block mediated by the fusion protein. Gene regulation by PLZF-RARα is associated with a complex set of chromatin changes mediated by a combination of histone deacetylases, methyl transferase and demethylases. All three classes of enzymes may represent therapeutic targets in t(11;17)-APL.

Physical and Functional Association of PLZF with Histone Methyl Transferase and Histone Demethylase.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 731-731
Author(s):  
Itsaso Hormaeche ◽  
Kim Rice ◽  
Joti Marango ◽  
Fabien Guidez ◽  
Arthur Zelent ◽  
...  
Keyword(s):  
Histone Methylation ◽  
Transcriptional Repression ◽  
Target Genes ◽  
Histone H3 ◽  
Promyelocytic Leukemia ◽  
Gene Repression ◽  
Histone Demethylases ◽  
Methyl Transferase ◽  
Histone Methyl Transferase

Abstract The promyelocytic leukemia zinc finger protein (PLZF) is a transcription factor fused to RARα in the t(11;17) translocation associated with retinoic acid resistant acute promyelocytic leukemia (APL). As a result of this chromosomal abnormality, two oncogenic proteins are produced, PLZF-RARα and RARα-PLZF. Wild type PLZF is expressed in CD34+ progenitor cells and declines during differentiation. PLZF is a tumor suppressor that causes cell cycle arrest, downregulating genes such as cyclinA2 and c-myc. We previously showed that transcriptional repression by PLZF is mediated by the recruitment of histone deacetylases to target genes, this being critical for its ability to control growth and affect RAR target genes. We now show that PLZF alters the methylation state of histones in its target genes. A biotinylated form of PLZF co-purified in cells along with a histone methyl transferase (HMT) activity for native histones. Using mutant histone H3 tail peptides, we showed that this activity methylated histone H3 on lysine 9 (H3K9me). Tagged forms of PLZF as well as endogenous PLZF co-precipitated in vivo with G9a histone methyl transferase, an enzyme that can mono and dimethylate H3K9 in euchromatin subject to gene repression. The interaction of PLZF with G9a required the presence of the N-terminal BTB/POZ domain as well as a second, more C-terminal, repression domain of PLZF. Given the newly found role of active histone demethylation in gene control we also tested the interaction of PLZF with LSD1, an enzyme associated with gene repression that demethylates H3K4. As in the case of G9a, the interaction of PLZF with LSD1 required both repression domains, suggesting, that these proteins may be part of a multi-protein complex containing multiple contact points with PLZF. Expression of G9a or LSD1 augmented transcriptional repression mediated by PLZF on reporter genes, indicating a functional interaction between histone methylation modifiers and PLZF. To determine the ability of PLZF to affect chromatin methylation in vivo, a Gal4-PLZF fusion protein was expressed in cells containing a chromatin-embedded Gal4-tk-Luciferase reporter gene. In the presence of PLZF, a chromatin immunoprecipitation experiment showed an increase in H3K9 methylation of the target gene while H3K4 methylation decreased, consistent with the ability of PLZF to interact with LSD1 and G9a. Lastly we compared the ability of the histone modifying proteins to interact with the APL fusion proteins PLZF-RARα, PML-RARα and NPM-RARα. Co-precipitation experiments showed a robust interaction between PLZF-RARα and G9a and LSD1 while the PML-RARα and NPM-RARα fusions bound these proteins significantly less avidly. Collectively all these data indicate that specific histone methylation is an important mode of action of PLZF in gene repression. The retinoic acid resistance of t(11;17)-APL may be related to its ability to interact with HMTs and histone demethylases. Hence therapeutic targeting of HMTs and histone demethylases might be considered as a novel mode of therapy in APL and other hematological malignancies.

scholarly journals Recruitment of N-CoR/SMRT-TBLR1 Corepressor Complex by Unliganded Thyroid Hormone Receptor for Gene Repression during Frog Development

2004 ◽  
Vol 24 (8) ◽  
pp. 3337-3346 ◽  
Author(s):  
Akihiro Tomita ◽  
Daniel R. Buchholz ◽  
Yun-Bo Shi
Keyword(s):  
Thyroid Hormone ◽  
Transcriptional Repression ◽  
Histone Deacetylases ◽  
Hormone Receptors ◽  
Thyroid Hormone Receptor ◽  
Histone Deacetylation ◽  
Gene Repression ◽  
Vertebrate Development ◽  
Inducible Promoters

ABSTRACT The corepressors N-CoR (nuclear receptor corepressor) and SMRT (silencing mediator for retinoid and thyroid hormone receptors) interact with unliganded nuclear hormone receptors, including thyroid hormone (T3) receptor (TR). Several N-CoR/SMRT complexes containing histone deacetylases have been purified. The best studied among them are N-CoR/SMRT complexes containing TBL1 (transducin beta-like protein 1) or TBLR1 (TBL1-related protein). Despite extensive studies of these complexes, there has been no direct in vivo evidence for the interaction of TBL1 or TBLR1 with TR or the possible involvement of such complexes in gene repression by any nuclear receptors in any animals. Here, we used the frog oocyte system to demonstrate that unliganded TR interacts with TBLR1 and recruits TBLR1 to its chromatinized target promoter in vivo, accompanied by histone deacetylation and gene repression. We further provide evidence to show that the recruitment of TBLR1 or related proteins is important for repression by unliganded TR. To investigate the potential role for TBLR1 complexes during vertebrate development, we made use of T3-dependent amphibian metamorphosis as a model. We found that TBLR1, SMRT, and N-CoR are recruited to T3-inducible promoters in premetamorphic tadpoles and are released upon T3 treatment, which induces metamorphosis. More importantly, we demonstrate that the dissociation of N-CoR/SMRT-TBLR1 complexes from endogenous TR target promoters is correlated with the activation of these genes during spontaneous metamorphosis. Taken together, our studies provide in vivo evidence for targeted recruitment of N-CoR/SMRT-TBLR1 complexes by unliganded TR in transcriptional repression during vertebrate development.

scholarly journals Regulation of p53 by Hypoxia: Dissociation of Transcriptional Repression and Apoptosis from p53-Dependent Transactivation

2001 ◽  
Vol 21 (4) ◽  
pp. 1297-1310 ◽  
Author(s):  
Constantinos Koumenis ◽  
Rodolfo Alarcon ◽  
Ester Hammond ◽  
Patrick Sutphin ◽  
William Hoffman ◽  
...  
Keyword(s):  
Dna Damage ◽  
Transcriptional Repression ◽  
Histone Deacetylases ◽  
Target Genes ◽  
P53 Protein ◽  
Genotoxic Stress ◽  
Protein Accumulation ◽  
Dependent Cell ◽  
Apoptotic Activity ◽  
Induced Apoptosis

ABSTRACT Hypoxic stress, like DNA damage, induces p53 protein accumulation and p53-dependent apoptosis in oncogenically transformed cells. Unlike DNA damage, hypoxia does not induce p53-dependent cell cycle arrest, suggesting that p53 activity is differentially regulated by these two stresses. Here we report that hypoxia induces p53 protein accumulation, but in contrast to DNA damage, hypoxia fails to induce endogenous downstream p53 effector mRNAs and proteins. Hypoxia does not inhibit the induction of p53 target genes by ionizing radiation, indicating that p53-dependent transactivation requires a DNA damage-inducible signal that is lacking under hypoxic treatment alone. At the molecular level, DNA damage induces the interaction of p53 with the transcriptional activator p300 as well as with the transcriptional corepressor mSin3A. In contrast, hypoxia primarily induces an interaction of p53 with mSin3A, but not with p300. Pretreatment of cells with an inhibitor of histone deacetylases that relieves transcriptional repression resulted in a significant reduction of p53-dependent transrepression and hypoxia-induced apoptosis. These results led us to propose a model in which different cellular pools of p53 can modulate transcriptional activity through interactions with transcriptional coactivators or corepressors. Genotoxic stress induces both kinds of interactions, whereas stresses that lack a DNA damage component as exemplified by hypoxia primarily induce interaction with corepressors. However, inhibition of either type of interaction can result in diminished apoptotic activity.

scholarly journals The Human Candidate Tumor Suppressor Gene HIC1 Recruits CtBP through a Degenerate GLDLSKK Motif

2002 ◽  
Vol 22 (13) ◽  
pp. 4890-4901 ◽  
Author(s):  
Sophie Deltour ◽  
Sébastien Pinte ◽  
Cateline Guerardel ◽  
Bohdan Wasylyk ◽  
Dominique Leprince
Keyword(s):  
Binding Site ◽  
Transcriptional Repression ◽  
Histone Deacetylases ◽  
Trichostatin A ◽  
Suppressor Gene ◽  
Close Relative ◽  
Consensus Binding Site ◽  
Candidate Tumor Suppressor Gene

ABSTRACT HIC1 (hypermethylated in cancer) and its close relative HRG22 (HIC1-related gene on chromosome 22) encode transcriptional repressors with five C2H2 zinc fingers and an N-terminal BTB/POZ autonomous transcriptional repression domain that is unable to recruit histone deacetylases (HDACs). Alignment of the HIC1 and HRG22 proteins from various species highlighted a perfectly conserved GLDLSKK/R motif highly related to the consensus CtBP interaction motif (PXDLSXK/R), except for the replacement of the virtually invariant proline by a glycine. HIC1 strongly interacts with mCtBP1 both in vivo and in vitro through this conserved GLDLSKK motif, thus extending the CtBP consensus binding site. The BTB/POZ domain does not interact with mCtBP1, but the dimerization of HIC1 through this domain is required for the interaction with mCtBP1. When tethered to DNA by fusion with the Gal4 DNA-binding domain, the HIC1 central region represses transcription through interactions with CtBP in a trichostatin A-sensitive manner. In conclusion, our results demonstrate that HIC1 mediates transcriptional repression by both HDAC-independent and HDAC-dependent mechanisms and show that CtBP is a HIC1 corepressor that is recruited via a variant binding site.

AML-1/ETO fusion protein is a dominant negative inhibitor of transcriptional repression by the promyelocytic leukemia zinc finger protein

Blood ◽  
2000 ◽  
Vol 96 (12) ◽  
pp. 3939-3947 ◽  
Author(s):  
Ari Melnick ◽  
Graeme W. Carlile ◽  
Melanie J. McConnell ◽  
Adam Polinger ◽  
Scott W. Hiebert ◽  
...  
Keyword(s):  
Fusion Protein ◽  
Zinc Finger ◽  
Transcriptional Repression ◽  
Target Genes ◽  
Zinc Finger Protein ◽  
Promyelocytic Leukemia ◽  
Dominant Negative ◽  
Myelogenous Leukemia ◽  
Promyelocytic Leukemia Zinc Finger ◽  
Dominant Negative Inhibitor

Abstract The AML-1/ETO fusion protein, created by the (8;21) translocation in M2-type acute myelogenous leukemia (AML), is a dominant repressive form of AML-1. This effect is due to the ability of the ETO portion of the protein to recruit co-repressors to promoters of AML-1 target genes. The t(11;17)(q21;q23)-associated acute promyelocytic leukemia creates the promyelocytic leukemia zinc finger PLZFt/RARα fusion protein and, in a similar manner, inhibits RARα target gene expression and myeloid differentiation. PLZF is expressed in hematopoietic progenitors and functions as a growth suppressor by repressing cyclin A2 and other targets. ETO is a corepressor for PLZF and potentiates transcriptional repression by linking PLZF to a histone deacetylase-containing complex. In transiently transfected cells and in a cell line derived from a patient with t(8;21) leukemia, PLZF and AML-1/ETO formed a tight complex. In transient assays, AML-1/ETO blocked transcriptional repression by PLZF, even at substoichiometric levels relative to PLZF. This effect was dependent on the presence of the ETO zinc finger domain, which recruits corepressors, and could not be rescued by overexpression of co-repressors that normally enhance PLZF repression. AML-1/ETO also excluded PLZF from the nuclear matrix and reduced its ability to bind to its cognate DNA-binding site. Finally, ETO interacted with PLZF/RARα and enhanced its ability to repress through the RARE. These data show a link in the transcriptional pathways of M2 and M3 leukemia.

scholarly journals In vivo analysis of the role of aberrant histone deacetylase recruitment and RARα blockade in the pathogenesis of acute promyelocytic leukemia

2006 ◽  
Vol 203 (4) ◽  
pp. 821-828 ◽  
Author(s):  
Hiromichi Matsushita ◽  
Pier Paolo Scaglioni ◽  
Mantu Bhaumik ◽  
Eduardo M. Rego ◽  
Lu Fan Cai ◽  
...  
Keyword(s):  
Retinoic Acid ◽  
Fusion Protein ◽  
Acute Promyelocytic Leukemia ◽  
Histone Deacetylases ◽  
Retinoic Acid Receptor ◽  
Promyelocytic Leukemia ◽  
Dominant Negative

The promyelocytic leukemia–retinoic acid receptor α (PML-RARα) protein of acute promyelocytic leukemia (APL) is oncogenic in vivo. It has been hypothesized that the ability of PML-RARα to inhibit RARα function through PML-dependent aberrant recruitment of histone deacetylases (HDACs) and chromatin remodeling is the key initiating event for leukemogenesis. To elucidate the role of HDAC in this process, we have generated HDAC1–RARα fusion proteins and tested their activity and oncogenicity in vitro and in vivo in transgenic mice (TM). In parallel, we studied the in vivo leukemogenic potential of dominant negative (DN) and truncated RARα mutants, as well as that of PML-RARα mutants that are insensitive to retinoic acid. Surprisingly, although HDAC1-RARα did act as a bona fide DN RARα mutant in cellular in vitro and in cell culture, this fusion protein, as well as other DN RARα mutants, did not cause a block in myeloid differentiation in vivo in TM and were not leukemogenic. Comparative analysis of these TM and of TM/PML−/− and p53−/− compound mutants lends support to a model by which the RARα and PML blockade is necessary, but not sufficient, for leukemogenesis and the PML domain of the fusion protein provides unique functions that are required for leukemia initiation.

FOG-1 Directly Binds to a Chromatin Remodeling and Deacetylase-Containing Complex To Mediate Transcriptional Repression by GATA-1.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 355-355
Author(s):  
Wei Hong ◽  
Minako Nakazawa ◽  
Ying-Yu Chen ◽  
Rajashree Kori ◽  
Carrie Rakowski ◽  
...  
Keyword(s):  
Transcriptional Repression ◽  
Histone Deacetylation ◽  
Gene Repression ◽  
Single Point Mutation ◽  
Mutant Form ◽  
Erythroid Cells ◽  
Binding Studies ◽  
Nucleosome Remodeling ◽  
N Terminus

Abstract Terminal erythroid maturation requires coordinated activation of erythroid marker genes and repression of genes associated with the undifferentiated state. These gene expression patterns are mediated by the concerted action of the erythroid transcription factor GATA-1 and its cofactor FOG-1 that can activate or repress transcription depending on promoter context. We and others showed previously that one mechanism by which FOG-1 functions is to facilitate GATA-1 association with certain DNA target sites in vivo. Using gene complementation studies of GATA-1-ablated erythroid cells, we show that at several GATA-1-repressed target genes (c-kit, c-myc and GATA-2) FOG-1 is dispensable for GATA-1 occupancy in vivo but essential for gene repression and histone deacetylation. To examine how FOG-1 functions as co-repressor we performed affinity chromatography, conventional protein purification and in vitro binding studies to identify proteins that bind FOG-1. We discovered that FOG-1 directly associates with the nucleosome remodeling and histone deacetylase complex NURD. This interaction is mediated by a small conserved domain at the N-terminus of FOG-1 and the MTA-1 subunit of NURD. Association of FOG-1 with NURD occurs in vivo and depends on an intact N-terminus of FOG-1. A series of point mutations across the N-terminus of FOG-1 revealed a tight correlation between NURD binding and transcriptional repression. In particular, a single point mutation at the N-terminus of FOG-1 that abrogated NURD binding also blocked gene repression by FOG-1. Finally, the ability of GATA-1 to repress transcription was impaired in erythroid cells expressing a mutant form of FOG-1 that is defective for NURD binding. Together, these studies show that FOG-1 and very likely other FOG proteins are bona fide co-repressors that link GATA proteins to histone deacetylation and nucleosome remodeling via a novel protein interaction module.

scholarly journals Transcriptional Repression of the Neurofibromatosis-1 Tumor Suppressor by the t(8;21) Fusion Protein

2005 ◽  
Vol 25 (14) ◽  
pp. 5869-5879 ◽  
Author(s):  
Genyan Yang ◽  
Waleed Khalaf ◽  
Louis van de Locht ◽  
Joop H. Jansen ◽  
Meihua Gao ◽  
...  
Keyword(s):  
Tumor Suppressor ◽  
Fusion Protein ◽  
Transcriptional Repression ◽  
Genetic Disorder ◽  
Suppressor Gene ◽  
Juvenile Myelomonocytic Leukemia ◽  
Increased Risk ◽  
Myeloid Progenitor Cells ◽  
Macrophage Colony

ABSTRACT Von Recklinghausen's disease is a relatively common familial genetic disorder characterized by inactivating mutations of the Neurofibromatosis-1 (NF1) gene that predisposes these patients to malignancies, including an increased risk for juvenile myelomonocytic leukemia. However, NF1 mutations are not common in acute myeloid leukemia (AML). Given that the RUNX1 transcription factor is the most common target for chromosomal translocations in acute leukemia, we asked if NF1 might be regulated by RUNX1. In reporter assays, RUNX1 activated the NF1 promoter and cooperated with C/EBPα and ETS2 to activate the NF1 promoter over 80-fold. Moreover, the t(8;21) fusion protein RUNX1-MTG8 (R/M), which represses RUNX1-regulated genes, actively repressed the NF1 promoter. R/M associated with the NF1 promoter in vivo and repressed endogenous NF1 gene expression. In addition, similar to loss of NF1, R/M expression enhanced the sensitivity of primary myeloid progenitor cells to granulocyte-macrophage colony-stimulating factor. Our results indicate that the NF1 tumor suppressor gene is a direct transcriptional target of RUNX1 and the t(8;21) fusion protein, suggesting that suppression of NF1 expression contributes to the molecular pathogenesis of AML.

scholarly journals Role of the C-Terminal Binding Protein PXDLS Motif Binding Cleft in Protein Interactions and Transcriptional Repression

2006 ◽  
Vol 26 (21) ◽  
pp. 8202-8213 ◽  
Author(s):  
Kate G. R. Quinlan ◽  
Alexis Verger ◽  
Alister Kwok ◽  
Stella H. Y. Lee ◽  
José Perdomo ◽  
...  
Keyword(s):  
Transcription Factors ◽  
Dna Binding ◽  
Protein Interactions ◽  
Transcriptional Repression ◽  
Histone Deacetylases ◽  
Gene Repression ◽  
Dna Binding Domains ◽  
Binding Domains ◽  
Binding Cleft ◽  
Partner Proteins

ABSTRACT C-terminal binding proteins (CtBPs) are multifunctional proteins that can mediate gene repression. CtBPs contain a cleft that binds Pro-X-Asp-Leu-Ser (PXDLS) motifs. PXDLS motifs occur in numerous transcription factors and in effectors of gene repression, such as certain histone deacetylases. CtBPs have been depicted as bridging proteins that self-associate and link PXDLS-containing transcription factors to PXDLS-containing chromatin-modifying enzymes. CtBPs also recruit effectors that do not contain recognizable PXDLS motifs. We have investigated the importance of the PXDLS binding cleft to CtBP's interactions with various partner proteins and to its ability to repress transcription. We used CtBP cleft mutant and cleft-filled fusion derivatives to distinguish between partner proteins that bind in the cleft and elsewhere on the CtBP surface. Functional assays demonstrate that CtBP mutants that carry defective clefts retain repression activity when fused to heterologous DNA-binding domains. This result suggests that the cleft is not essential for recruiting effectors. In contrast, when tested in the absence of a fused DNA-binding domain, disruption of the cleft abrogates repression activity. These results demonstrate that the PXDLS binding cleft is functionally important but suggest that it is primarily required for localization of the CtBP complex to promoter-bound transcription factors.

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