Single-Stranded DNA-Binding Transcriptional Regulator FUBP1 Is Essential for Fetal and Adult Hematopoietic Stem Cell Self-Renewal

Rabenhorst, Uta; Thalheimer, Frederic B.; Gerlach, Katharina; Kijonka, Marek; Böhm, Stefanie; Krause, Daniela; Vauti, Franz; Arnold, Hans-Henning; Schroeder, Timm; Schnütgen, Frank; Melchner, Harald von; Rieger, Michael A.; Zörnig, Martin

doi:10.1016/j.celrep.2015.05.038

Cited by 33 publications

(49 citation statements)

References 33 publications

(38 reference statements)

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“…Contrary to the results here, the investigators report that HSCs of FBP-deficient mice proliferate poorly but differentiate properly. 47 Note that this study relied on gene-trap and shRNA targeting of the Fubp1 allele or its mRNA; neither of these methods assures the complete absence of functional FBP as guaranteed by the germline deletion of the FBP's nucleic acid binding domain in the current experiments. Hypomorphic but not null FBP activity in these systems is strongly suggested by comparison of the competitive transplantation assays.…”

Section: Discussionmentioning

confidence: 99%

Far Upstream Element Binding Protein Plays a Crucial Role in Embryonic Development, Hematopoiesis, and Stabilizing Myc Expression Levels

Zhou

Chung

Castellar

et al. 2016

The American Journal of Pathology

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The transcription factor far upstream element binding protein (FBP) binds and activates the MYC promoter when far upstream element is via TFIIH helicase activity early in the transcription cycle. The fundamental biology and pathology of FBP are complex. In some tumors FBP seems pro-oncogenic, whereas in others it is a tumor suppressor. We generated an FBP knockout (Fubp1 À/À ) mouse to study FBP deficiency. FBP is embryo lethal from embryonic day 10.5 to birth. A spectrum of pathology is associated with FBP loss; besides cerebral hyperplasia and pulmonary hypoplasia, pale livers, hypoplastic spleen, thymus, and bone marrow, cardiac hypertrophy, placental distress, and small size were all indicative of anemia. Immunophenotyping of hematopoietic cells in wild-type versus knockout livers revealed irregular trilineage anemia, with deficits in colony formation. Despite normal numbers of hematopoietic stem cells, transplantation of Fubp1 À/À hematopoietic stem cells into irradiated mice entirely failed to reconstitute hematopoiesis. In competitive transplantation assays against wild-type donor bone marrow, Fubp1 À/À hematopoietic stem cells functioned only sporadically at a low level. Although cultures of wild-type mouse embryo fibroblasts set Myc levels precisely, Myc levels of mouse varied wildly between fibroblasts harvested from different Fubp1 À/À embryos, suggesting that FBP contributes to Myc set point fixation. FBP helps to hold multiple physiologic processes to close tolerances, at least in part by constraining Myc expression. The transcription factor Myc plays a decisive role in cell growth, differentiation, and senescence and so must be highly regulated. The far upstream element (FUSE) binding protein (FBP) binds single-stranded DNA of FUSE 1.7 kb upstream of the major P2 promoter of the human MYC gene. 1e3 FUSE melting in response to dynamic supercoils propagated from the MYC promoters enables FBP binding. FBP activates TFIIH helicase activity to accelerate the transcription cycle from preinitiation complex assembly through promoter escape and onto pause release. 4e6 Positive regulation of MYC is at least in part counteracted by FBP interacting repressor (FIR) that binds FBP and FUSE and opposes TFIIH helicase activity, retarding the transcription cycle. 5,7 Besides MYC, FBP regulates the expression of the cyclin-dependent kinase inhibitor p21, stathmin, and USP29, a powerful stabilizer of p53 induced by oxidative stress. 8e10 Because the FBP/FIR system reads single-stranded DNA sequences exposed by transcriptionally generated dynamic supercoiling, it is proposed that the FBP/ FIR/FUSE system serves as a molecular cruise control that monitors the mechanical output of promoters in real time while providing both positive and negative feedback. 11e13Supported by the NIH

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Section: Discussionmentioning

confidence: 99%

Far Upstream Element Binding Protein Plays a Crucial Role in Embryonic Development, Hematopoiesis, and Stabilizing Myc Expression Levels

Zhou

Chung

Castellar

et al. 2016

The American Journal of Pathology

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“…FUBP1 knockdown in human hepatocellular carcinoma (HCC) cell lines also decreases proliferation, and impairs tumour formation in mouse xenograft models [127]. Essential functions in HSC self-renewal were revealed using Fubp1 gene trap mice, with embryonic lethality (around E15.5) associated with anaemia [128]. Secondary transplantation assays for long-term repopulating hematopoietic stem cells (LT-HSCs) revealed reduced blood cell reconstitution for Fubp1 knockdown.…”

Section: Developmental Function Of Fubp1mentioning

confidence: 99%

“…Secondary transplantation assays for long-term repopulating hematopoietic stem cells (LT-HSCs) revealed reduced blood cell reconstitution for Fubp1 knockdown. Fubp1 -deficient adult HSCs exhibited increased expression of key cell cycle (cyclin-dependent kinase inhibitor, p21 ) and pro-apoptotic ( Noxa ) genes based on mRNA expression profile data [128]. Given that the haematopoietic lineage displays specific sensitivity to MYC levels [32], and the ability of MYC to repress p21 expression [129], the Fubp1 knockout phenotype suggests that MYC could be a key downstream target that mediates these effects.…”

Section: Developmental Function Of Fubp1mentioning

confidence: 99%

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Controlling the Master: Chromatin Dynamics at the MYC Promoter Integrate Developmental Signaling

Zaytseva

Quinn

2017

Genes

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The transcription factor and cell growth regulator MYC is potently oncogenic and estimated to contribute to most cancers. Decades of attempts to therapeutically target MYC directly have not resulted in feasible clinical applications, and efforts have moved toward indirectly targeting MYC expression, function and/or activity to treat MYC-driven cancer. A multitude of developmental and growth signaling pathways converge on the MYC promoter to modulate transcription through their downstream effectors. Critically, even small increases in MYC abundance (<2 fold) are sufficient to drive overproliferation; however, the details of how oncogenic/growth signaling networks regulate MYC at the level of transcription remain nebulous even during normal development. It is therefore essential to first decipher mechanisms of growth signal-stimulated MYC transcription using in vivo models, with intact signaling environments, to determine exactly how these networks are dysregulated in human cancer. This in turn will provide new modalities and approaches to treat MYC-driven malignancy. Drosophila genetic studies have shed much light on how complex networks signal to transcription factors and enhancers to orchestrate Drosophila MYC (dMYC) transcription, and thus growth and patterning of complex multicellular tissue and organs. This review will discuss the many pathways implicated in patterning MYC transcription during development and the molecular events at the MYC promoter that link signaling to expression. Attention will also be drawn to parallels between mammalian and fly regulation of MYC at the level of transcription.

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“…Early studies demonstrated that reduced FUBP1 is required for MYC expression and proliferation in ex vivo cultured cells. 35,36 Recent FUBP1 gene trap 37 and knockout studies 38 revealed essential functions in haematopoietic stem cell (HSC) self-renewal, which is associated with anaemia and embryonic lethality. Interestingly, MYC mRNA levels vary drastically between individual ex vivo cultures of FUBP1 knockout mouse embryo fibroblasts (MEFs) harvested from different FUBP1 embryos.…”

Section: Developmental Function Of Fubp1mentioning

confidence: 99%

FUBP/KH domain proteins in transcription: Back to the future

Quinn

2017

Transcription

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Drosophila genetic studies demonstrate that cell and tissue growth regulation is a primary developmental function of P-element somatic inhibitor (Psi), the sole ortholog of FUBP family RNA/ DNA-binding proteins. Psi achieves growth control through interaction with Mediator, observations that should put to rest controversy surrounding Pol II transcriptional functions for these KH domain proteins. KEYWORDSDrosophila; FUBP1; Growth control; MYC; Psi PrefaceHere I provide an historical perspective on the FUBP family of KH domain proteins in transcription, starting »25 years ago with discovery of FUBP1s single stranded DNA (ssDNA) binding function, and implication in activating transcription of the MYC oncogene.1-3 Despite the decades that have passed, the transcriptional function of the FUBP family remains somewhat controversial; most literature attributes RNA-binding functions, both as negative and positive regulators of mRNA splicing, mRNA stability, mRNA export and mRNA translation (reviewed in Ref. 4 ). The dogma remains: RNA processing constitutes the primary role of FUBP proteins, while interaction with ssDNA to elicit transcriptional control is a lesser function. Moreover, as evidence toward understanding FUBP1 function has been gathered primarily using mammalian systems, where function can be obscured by redundancy between multiple family members, key physiologic roles have remained unclear. Recent Drosophila genetic studies revealed a major developmental function of the sole FUBP ortholog (Psi); interaction with the RNA Polymerase II (Pol II) Mediator complex, regulation of MYC expression and control of cell and tissue growth. FUSE-a nuclease-sensitive site in the MYC promoter modulates transcriptionEven small changes in abundance of the MYC oncoprotein can significantly alter cell growth and proliferation, 6 hallmarks of cancer. The interest in MYC promoter regulation was fuelled by the observation that translocated MYC alleles in Burkitt's Lymphoma that contain either truncated or mutated exon 1.7,8 Analysis of the endogenous MYC promoter in human leukemia cell lines revealed that induction of differentiation, and transcriptional downregulation of MYC, was associated with a block to Pol II elongation. 9 The exon 1 mutation prevents the Pol II block and leads to constitutive Pol II read-through and elevated MYC. 8,[10][11][12] The complexity of the MYC promoter and regulation by post-initiation release of paused Pol II reflects the multitude of signaling inputs converging on MYC transcription. As early studies found a correlation between MYC promoter sensitivity to nuclease cleavage and expression levels, 9,10,13 analysis of nucleasesensitive elements was used as a means to understand integration of signaling inputs. Interestingly, of the multiple regions containing sequence-specific binding sites predicted for MYC regulators, only the region 1.5kb upstream of the P1 promoter lost binding activity, following induced differentiation and downregulation of MYC expression.

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Single-Stranded DNA-Binding Transcriptional Regulator FUBP1 Is Essential for Fetal and Adult Hematopoietic Stem Cell Self-Renewal

Cited by 33 publications

References 33 publications

Far Upstream Element Binding Protein Plays a Crucial Role in Embryonic Development, Hematopoiesis, and Stabilizing Myc Expression Levels

Far Upstream Element Binding Protein Plays a Crucial Role in Embryonic Development, Hematopoiesis, and Stabilizing Myc Expression Levels

Controlling the Master: Chromatin Dynamics at the MYC Promoter Integrate Developmental Signaling

FUBP/KH domain proteins in transcription: Back to the future

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