Disease relevance of SPI1

• To identify a novel protein(s) binding to PU.1, we carried out affinity purification using a column of Glutathione-Sepharose beads bound to GST-PU.1 fusion protein and isolated several individual proteins using murine erythroleukemia (MEL) cell extracts [1].
• Wild-type Salmonella typhimurium and an isogenic SPI-1 type three secretion system (TTSS) mutant derivative (invA) were used to compare the interactions with 3-D cells and monolayers in adherence/invasion, tissue pathology, and cytokine expression studies [2].
• Alterations of loci encoding PU.1, BOB1, and OCT2 transcription regulators do not correlate with their suppressed expression in Hodgkin lymphoma [3].
• 1. In addition, the single-base mutation (C --> T) at position -52 that was identified in a patient with chronic granulomatous disease inhibited the binding of PU.1 to the promoter [4].
• The myeloid master regulator transcription factor PU.1 is inactivated by AML1-ETO in t(8;21) myeloid leukemia [5].

High impact information on SPI1

• Using PU.1(-/-) progenitors, we demonstrate that at subthreshold levels, this Ets transcription factor regulates a mixed pattern (macrophage/neutrophil) of gene expression within individual myeloid progenitors [6].
• Essential role of Jun family transcription factors in PU.1 knockdown-induced leukemic stem cells [7].
• Examination of human individuals with AML confirmed the correlation between PU.1 and JunB downregulation [7].
• We examined the transcriptome of preleukemic hematopoietic stem cells (HSCs) in which PU.1 was knocked down (referred to as 'PU.1-knockdown HSCs') to identify transcriptional changes preceding malignant transformation [7].
• The microA motif was required for microB-dependent enhancer activity, which suggests that a minimal B cell-specific enhancer is composed of both the PU.1 and Ets-1 binding sites [8].

Chemical compound and disease context of SPI1

• Lastly, we found that mutation of PU.1 at serine 148, which prevents its phosphorylation by CK2, blocked its ability to activate the HIV-1 LTR in response to LPS [9].
• PU.1 reduced expression of integrin beta(5), a host factor important for endosomal escape of adenovirus, suggesting that PU.1 redirects adenoviral trafficking by modulating integrin signaling [10].
• Both PU.1 and nuclear factor-kappa B mediate lipopolysaccharide- induced HIV-1 long terminal repeat transcription in macrophages [9].

Biological context of SPI1

• Localization of the human oncogene SPI1 on chromosome 11, region p11.22 [11].
• The genes encoding for these three respective transcription factors have been mapped at 11p11.2 (SPI1), 11q23.1 (POU2AF1), and 19q13.2 (POU2F2); these are chromosomes recurrently affected in HL [3].
• Finally, PU.1 protein can inhibit both GATA-1 and GATA-2 transactivation function [12].
• Addition of ETS1 and FLI1, two ETS family members that have homology in the 5' HLH region, but not Spi1, an ETS family member without the 5' HLH region, also inhibited reporter gene expression [13].
• We show that in B cells, E47 and PU.1/IRF-4 interact with the E-box motifs and the EICE, respectively, and act synergistically in the activation of CIITA-PIII [14].

Anatomical context of SPI1

• Our results suggest that interactions between PU.1 and GATA proteins play a critical role in the decision of stem cells to commit to erythroid vs. myeloid lineages [12].
• Novel combinatorial interactions of GATA-1, PU.1, and C/EBPepsilon isoforms regulate transcription of the gene encoding eosinophil granule major basic protein [15].
• In Jurkat cells, overexpression of c-Ets-1, c-Ets-2, or PU.1 effectively represses dexamethasone-mediated up-regulation of an hGR 1A promoter-luciferase reporter gene, as do dominant negative c-Myb (c-Myb DNA-binding domain) or Ets proteins (Ets-2 DNA-binding domain) [16].
• Ectopic expression of Oct-2 was able to fully restore PU.1 promoter activity in the PEL cell line BCBL-1, while PU.1 expression also reconstituted the activity of the lambdaB Ets-IRF site [17].
• Finally, we showed that the silencer is also active in TAL-1-negative myeloid HL60 cells that express PU.1 at high levels [18].

Associations of SPI1 with chemical compounds

• Two of these genes, glutathione peroxidase (GPx) and serine leukoprotease inhibitor, are involved in protecting neutrophils from the products they make to destroy pathogens and were analyzed further to determine if PU.1 directly regulates their expression [19].
• Use of stable cloned HL-60 cells that contained a reporter vector for monitoring the activity of the transcription factor PU.1, which acts specifically at the stage of promyelocyte differentiation into neutrophils and monocytes, revealed that indirubin has a potent promoting activity on intracellular PU [20].
• Interferon-gamma and retinoic acid downregulated PU.1 expression in marrow macrophages [21].
• Promoter activity and transcript levels of p40(phox) increased in HL-60 cells during dimethyl sulfoxide-induced differentiation toward the granulocyte phenotype, and this was associated with increased cellular levels of PU.1 protein [22].
• Functional interference between the Spi-1/PU.1 oncoprotein and steroid hormone or vitamin receptors [23].

Physical interactions of SPI1

• We demonstrate further that GATA inhibits binding of PU.1 to c-Jun, a critical coactivator of PU.1 transactivation of myeloid promoters [12].
• Like E1A, PU.1 binds to the conserved C-terminal domain of TFIID and to the RB "pocket" domain [24].
• Here we present evidence that the cellular transcription factor PU.1 can bind to both RB and TFIID [24].
• PU.1/Spi-1 binds to the human TAL-1 silencer to mediate its activity [18].
• During the onset and normal progression of hematopoiesis, several lineage-specific factors such as C/EBPalpha and PU.1 interact with Runx1 to regulate transcription combinatorially [25].

Regulatory relationships of SPI1

• Negative cross-talk between hematopoietic regulators: GATA proteins repress PU.1 [12].
• Carrier-independent nuclear import of the transcription factor PU.1 via RanGTP-stimulated binding to Nup153 [26].
• MeCP2 repressed transcriptional activity of PU.1 on a reporter construct with trimerized PU.1 binding sites [1].
• PU.1 regulates glutathione peroxidase expression in neutrophils [19].
• VIP inhibited the nuclear translocation of PU.1 in LPS-stimulated THP-1 monocytes [27].

Other interactions of SPI1

• PU.1 (also known as Spi-1) and GATA-1 are transcription factors essential for the development of myeloid and erythroid lineages, respectively [12].
• The ability of PU.1 to contact directly both RB and TFIID through the same 75-residue domain prompted us to look for sequence similarity between these two proteins [24].
• The Ets domain accounted for the bulk of the interaction of PU.1 with Nup153 and RanGMPPNP [26].
• Our results suggest that MeCP2 acts as a corepressor of PU.1 probably due to facilitating complex formation with mSin3A and HDACs [1].
• The mechanism of action of VIP on monocyte differentiation may be via inhibition of the transcription factor PU.1 [27].

Analytical, diagnostic and therapeutic context of SPI1

• Co-immunoprecipitations using lysates of AML14.3D10 eosinophils show that both C/EBPepsilon(32/30) and epsilon(27) physically interact in vivo with PU.1 and GATA-1, demonstrating functional interactions among these factors in eosinophil progenitors [15].
• Electrophoretic mobility shift assay revealed that the activity of a transcription factor PU.1 was also downregulated by E. chaffeensis infection [28].
• We show for the first time that PU.1 mRNA expression in PAP bronchoalveolar lavage cells is deficient compared with healthy controls [29].
• To check the genomic status of PU.1, BOB1, and OCT2 in HL, we performed metaphase fluorescence in situ hybridization (FISH) analysis of 10 HL cases using locus-specific bacterial artificial chromosome clones [3].
• In situ immunohistochemistry found that PU.1 is expressed only in early granulocytic and erythroid cells and megakaryocytes, but not in mature erythroid cells, mature granulocytes, endothelial cells, or osteocytes [21].

References