GATA Switches as Developmental Drivers

HIV-1 infection is associated with increased risk for B-cell lymphomas. How HIV infection promotes the development of lymphoma is unclear, but it may involve chronic B-cell activation, inflammation, and/or impaired immunity, possibly leading to a loss of control of oncogenic viruses and reduced tumor immunosurveillance. We hypothesized that HIV structural proteins may contribute to lymphomagenesis directly, because they can persist long term in lymph nodes in the absence of viral replication. The HIV-1 transgenic mouse Tg26 carries a noninfectious HIV-1 provirus lacking part of the gag-pol region, thus constituting a model for studying the effects of viral products in pathogenesis. Approximately 15% of Tg26 mice spontaneously develop leukemia/lymphoma. We investigated which viral proteins are associated with the development of leukemia/lymphoma in the Tg26 mouse model, and performed microarray analysis on RNA from spleen and lymph nodes to identify potential mechanisms of lymphomagenesis. Of the viral proteins examined, only expression of HIV-1 matrix protein p17 was associated with leukemia/lymphoma development and was highly expressed in bone marrow before disease. The tumor cells resembled pro-B cells, and were CD19(+)IgM(-)IgD(-)CD93(+)CD43(+)CD21(-)CD23(-)VpreB(+)CXCR4(+) Consistent with the pro-B-cell stage of B-cell development, microarray analysis revealed enrichment of transcripts, including Rag1, Rag2, CD93, Vpreb1, Vpreb3, and Igll1 We confirmed RAG1 expression in Tg26 tumors, and hypothesized that HIV-1 matrix protein p17 may directly induce RAG1 in B cells. Stimulation of human activated B cells with p17 enhanced RAG1 expression in three of seven donors, suggesting that intracellular signaling by p17 may lead to genomic instability and transformation

Section: Discussionsupporting

confidence: 51%

Expression of HIV-1 matrix protein p17 and association with B-cell lymphoma in HIV-1 transgenic mice

Carroll

Lafferty

Marchionni

et al. 2016

“…Because GATA-2 occupies these prospective regulatory sites in erythroid precursor cells lacking GATA-1, we proposed that this reflects GATA-2-mediated positive autoregulation (10). Because GATA-1 is expressed during erythropoiesis, it displaces GATA-2, instigating Gata2 repression (24). GATA-1-mediated displacement of GATA-2 from chromatin is termed GATA switching, and the GATA factor-occupied sites are deemed GATA switch sites (10,24).…”

mentioning

confidence: 99%

“…Because GATA-1 is expressed during erythropoiesis, it displaces GATA-2, instigating Gata2 repression (24). GATA-1-mediated displacement of GATA-2 from chromatin is termed GATA switching, and the GATA factor-occupied sites are deemed GATA switch sites (10,24).…”

mentioning

confidence: 99%

Mechanism governing a stem cell-generating cis -regulatory element

Sanalkumar

Johnson

Gào

et al. 2014

Self Cite

The unremitting demand to replenish differentiated cells in tissues requires efficient mechanisms to generate and regulate stem and progenitor cells. Although master regulatory transcription factors, including GATA binding protein-2 (GATA-2), have crucial roles in these mechanisms, how such factors are controlled in developmentally dynamic systems is poorly understood. Previously, we described five dispersed Gata2 locus sequences, termed the −77, −3.9, −2.8, −1.8, and +9.5 GATA switch sites, which contain evolutionarily conserved GATA motifs occupied by GATA-2 and GATA-1 in hematopoietic precursors and erythroid cells, respectively. Despite common attributes of transcriptional enhancers, targeted deletions of the −2.8, −1.8, and +9.5 sites revealed distinct and unpredictable contributions to Gata2 expression and hematopoiesis. Herein, we describe the targeted deletion of the −3.9 site and mechanistically compare the −3.9 site with other GATA switch sites. The −3.9 −/− mice were viable and exhibited normal Gata2 expression and steady-state hematopoiesis in the embryo and adult. We established a Gata2 repression/reactivation assay, which revealed unique +9.5 site activity to mediate GATA factor-dependent chromatin structural transitions. Loss-of-function analyses provided evidence for a mechanism in which a mediator of long-range transcriptional control [LIM domain binding 1 (LDB1)] and a chromatin remodeler [Brahma related gene 1 (BRG1)] synergize through the +9.5 site, conferring expression of GATA-2, which is known to promote the genesis and survival of hematopoietic stem cells.cis element | HSCs W hereas proximal promoter sequences assemble the basal transcriptional machinery and RNA polymerase, distant cis-regulatory elements often confer tissue-specific or contextdependent transcriptional regulation. Enhancer elements reside many kilobases upstream or downstream of a promoter or within introns, and extensive efforts have focused on elucidating "action-at-a-distance" mechanisms (1). Long-range transcriptional control involves physical interactions between proteins bound at distal regions and promoter sequences and higher order structural transitions, including subnuclear relocalization of target loci (2-4). Given the high frequency of long-range mechanisms at mammalian loci and the mutations that disrupt the function of such elements in pathological conditions, elucidating the underlying mechanisms in development,

“…The transcription factor GATA-2 (2, 3) is required for the genesis and maintenance of HSCs (4), whereas GATA-1 (5, 6) is crucial for erythrocyte, megakaryocyte, mast cell, and eosinophil development (7,8). During erythropoiesis, GATA-1 replaces GATA-2 at Gata2 chromatin sites, thus conferring repression (9)(10)(11). GATA switches occur at numerous loci and are frequently associated with altered transcriptional output.…”

mentioning

confidence: 99%

Establishing a hematopoietic genetic network through locus-specific integration of chromatin regulators

DeVilbiss

Boyer

Bresnick

2013

Self Cite

The establishment and maintenance of cell type-specific transcriptional programs require an ensemble of broadly expressed chromatin remodeling and modifying enzymes. Many questions remain unanswered regarding the contributions of these enzymes to specialized genetic networks that control critical processes, such as lineage commitment and cellular differentiation. We have been addressing this problem in the context of erythrocyte development driven by the transcription factor GATA-1 and its coregulator Friend of GATA-1 (FOG-1). As certain GATA-1 target genes have little to no FOG-1 requirement for expression, presumably additional coregulators can mediate GATA-1 function. Using a genetic complementation assay and RNA interference in GATA-1-null cells, we demonstrate a vital link between GATA-1 and the histone H4 lysine 20 methyltransferase PR-Set7/SetD8 (SetD8). GATA-1 selectively induced H4 monomethylated lysine 20 at repressed, but not activated, loci, and endogenous SetD8 mediated GATA-1-dependent repression of a cohort of its target genes. GATA-1 used different combinations of SetD8, FOG-1, and the FOG-1-interacting nucleosome remodeling and deacetylase complex component Mi2β to repress distinct target genes. Implicating SetD8 as a context-dependent GATA-1 corepressor expands the repertoire of coregulators mediating establishment/maintenance of the erythroid cell genetic network, and provides a biological framework for dissecting the cell type-specific functions of this important coregulator. We propose a coregulator matrix model in which distinct combinations of chromatin regulators are required at different GATA-1 target genes, and the unique attributes of the target loci mandate these combinations.