scholarly journals E2a-Pbx1 induces aberrant expression of tissue-specific and developmentally regulated genes when expressed in NIH 3T3 fibroblasts.

1997 ◽  
Vol 17 (3) ◽  
pp. 1503-1512 ◽  
Author(s):  
X Fu ◽  
M P Kamps

The E2a-Pbx1 oncoprotein contains the transactivation domain of E2a joined to the DNA-binding homeodomain (HD) of Pbx1. In mice, E2a-Pbx1 transforms T lymphoblasts and fibroblasts and blocks myeloblast differentiation. Pbx1 and E2a-Pbx1 bind DNA as heterodimers with other HD proteins whose expression is tissue specific. While the transactivation domain of E2a is required for all forms of transformation, DNA binding by the Pbx1 HD is essential for blocking myeloblast differentiation but dispensable for fibroblast or T-lymphoblast transformation. These properties suggest (i) that E2a-Pbx1 causes cellular transformation by activating gene transcription, (ii) that transcription of E2a-Pbx1 target genes is normally regulated by ubiquitous Pbx proteins and tissue-specific partners, and (iii) that DNA-binding mutants of E2a-Pbx1 activate a subset of all gene targets. To test these predictions, genes induced in NIH 3T3 fibroblasts by E2a-Pbx1 were identified and examined for tissue- and stage-specific expression and their differential abilities to be upregulated by E2a-Pbx1 in NIH 3T3 fibroblasts and myeloblasts and by a DNA-binding mutant of E2a-Pbx1 in NIH 3T3 cells. Of 12 RNAs induced by E2a-Pbx1, 4 encoded known proteins (a J-C region of the immunoglobulin kappa light chain, natriuretic peptide receptor C, mitochondrial fumarase, and the 3',5'-cyclic nucleotide phosphodiesterase, PDE1A) and 5 encoded new proteins related to angiogenin, ion channels, villin, epidermal growth factor repeat proteins, and the human 2.19 gene product. Expression of many of these genes was tissue specific or developmentally regulated, and most were not expressed in fibroblasts, indicating that E2a-Pbx1 can induce ectopic expression of genes associated with lineage-specific differentiation.

2020 ◽  
Vol 21 (24) ◽  
pp. 9401
Author(s):  
Antonio Bouthelier ◽  
Florinda Meléndez-Rodríguez ◽  
Andrés A. Urrutia ◽  
Julián Aragonés

Cellular response to hypoxia is controlled by the hypoxia-inducible transcription factors HIF1α and HIF2α. Some genes are preferentially induced by HIF1α or HIF2α, as has been explored in some cell models and for particular sets of genes. Here we have extended this analysis to other HIF-dependent genes using in vitro WT8 renal carcinoma cells and in vivo conditional Vhl-deficient mice models. Moreover, we generated chimeric HIF1/2 transcription factors to study the contribution of the HIF1α and HIF2α DNA binding/heterodimerization and transactivation domains to HIF target specificity. We show that the induction of HIF1α-dependent genes in WT8 cells, such as CAIX (CAR9) and BNIP3, requires both halves of HIF, whereas the HIF2α transactivation domain is more relevant for the induction of HIF2 target genes like the amino acid carrier SLC7A5. The HIF selectivity for some genes in WT8 cells is conserved in Vhl-deficient lung and liver tissue, whereas other genes like Glut1 (Slc2a1) behave distinctly in these tissues. Therefore the relative contribution of the DNA binding/heterodimerization and transactivation domains for HIF target selectivity can be different when comparing HIF1α or HIF2α isoforms, and that HIF target gene specificity is conserved in human and mouse cells for some of the genes analyzed.


1993 ◽  
Vol 13 (3) ◽  
pp. 1824-1835 ◽  
Author(s):  
A Aoyama ◽  
E Fröhli ◽  
R Schäfer ◽  
R Klemenz

alpha B-crystallin, a major soluble protein of vertebrate eye lenses, is a small heat shock protein which transiently accumulates in response to heat shock and other kinds of stress in mouse NIH 3T3 fibroblasts. Ectopic expression of an alpha B-crystallin cDNA clone renders NIH 3T3 cells thermoresistant. alpha B-crystallin accumulates in response to the synthetic glucocorticoid hormone dexamethasone. Dexamethasone-treated NIH 3T3 cells become thermoresistant to the same extent as they accumulate alpha B-crystallin. A cell clone in which alpha B-crystallin is superinduced upon heat shock acquires augmented thermotolerance. Expression of the ras oncogene causes a rapid but transient accumulation of alpha B-crystallin within 1 day. Later, sustained ras oncogene expression suppresses the dexamethasone-mediated alpha B-crystallin accumulation. Thus, oncogenic transformation triggered by the ras oncogene interferes with hormone-mediated accumulation of alpha B-crystallin and concomitant acquisition of thermoresistance. Other known heat shock proteins do not accumulate in response to ectopic alpha B-crystallin expression or to dexamethasone treatment. These results indicate that alpha B-crystallin can protect NIH 3T3 fibroblasts from thermal shock.


1999 ◽  
Vol 19 (1) ◽  
pp. 594-601 ◽  
Author(s):  
Paula Y. P. Lam ◽  
Jack E. Sublett ◽  
Andrew D. Hollenbach ◽  
Martine F. Roussel

ABSTRACT The chimeric transcription factor Pax3-FKHR, produced by the t(2;13)(q35;q14) chromosomal translocation in alveolar rhabdomyosarcoma, consists of the two Pax3 DNA binding domains (paired box and homeodomain) fused to the C-terminal forkhead (FKHR) sequences that contain a potent transcriptional activation domain. To determine which of these domains are required for cellular transformation, Pax3, Pax3-FKHR, and selected mutants were retrovirally expressed in NIH 3T3 cells and evaluated for their capacity to promote anchorage-independent cell growth. Mutational analysis revealed that both the third α-helix of the homeodomain and a small region of the FKHR transactivation domain are absolutely required for efficient transformation by the Pax3-FKHR fusion protein. Surprisingly, point mutations in the paired domain that abrogate sequence-specific DNA binding retained transformation potential equivalent to that of the wild-type protein. This finding suggests that DNA binding mediated through the Pax3 paired box is not required for transformation. Our results demonstrate that the integrity of the Pax3 homeodomain recognition helix and the FKHR transactivation domain is necessary for efficient cellular transformation by the Pax3-FKHR fusion protein.


2007 ◽  
Vol 27 (6) ◽  
pp. 2059-2073 ◽  
Author(s):  
Victoria H. Cowling ◽  
Michael D. Cole

ABSTRACT Myc is a transcription factor which is dependent on its DNA binding domain for transcriptional regulation of target genes. Here, we report the surprising finding that Myc mutants devoid of direct DNA binding activity and Myc target gene regulation can rescue a substantial fraction of the growth defect in myc −/− fibroblasts. Expression of the Myc transactivation domain alone induces a transcription-independent elevation of the RNA polymerase II (Pol II) C-terminal domain (CTD) kinases cyclin-dependent kinase 7 (CDK7) and CDK9 and a global increase in CTD phosphorylation. The Myc transactivation domain binds to the transcription initiation sites of these promoters and stimulates TFIIH binding in an MBII-dependent manner. Expression of the Myc transactivation domain increases CDK mRNA cap methylation, polysome loading, and the rate of translation. We find that some traditional Myc transcriptional target genes are also regulated by this Myc-driven translation mechanism. We propose that Myc transactivation domain-driven RNA Pol II CTD phosphorylation has broad effects on both transcription and mRNA metabolism.


2018 ◽  
Vol 116 (3) ◽  
pp. 890-899 ◽  
Author(s):  
Na Liu ◽  
Junhong Song ◽  
Yangyang Xie ◽  
Xiao-Lin Wang ◽  
Bowen Rong ◽  
...  

The AML1-ETO fusion protein, generated by the t(8;21) chromosomal translocation, is causally involved in nearly 20% of acute myeloid leukemia (AML) cases. In leukemic cells, AML1-ETO resides in and functions through a stable protein complex, AML1-ETO–containing transcription factor complex (AETFC), that contains multiple transcription (co)factors. Among these AETFC components, HEB and E2A, two members of the ubiquitously expressed E proteins, directly interact with AML1-ETO, confer new DNA-binding capacity to AETFC, and are essential for leukemogenesis. However, the third E protein, E2-2, is specifically silenced in AML1-ETO–expressing leukemic cells, suggesting E2-2 as a negative factor of leukemogenesis. Indeed, ectopic expression of E2-2 selectively inhibits the growth of AML1-ETO–expressing leukemic cells, and this inhibition requires the bHLH DNA-binding domain. RNA-seq and ChIP-seq analyses reveal that, despite some overlap, the three E proteins differentially regulate many target genes. In particular, studies show that E2-2 both redistributes AETFC to, and activates, some genes associated with dendritic cell differentiation and represses MYC target genes. In AML patients, the expression of E2-2 is relatively lower in the t(8;21) subtype, and an E2-2 target gene, THPO, is identified as a potential predictor of relapse. In a mouse model of human t(8;21) leukemia, E2-2 suppression accelerates leukemogenesis. Taken together, these results reveal that, in contrast to HEB and E2A, which facilitate AML1-ETO–mediated leukemogenesis, E2-2 compromises the function of AETFC and negatively regulates leukemogenesis. The three E proteins thus define a heterogeneity of AETFC, which improves our understanding of the precise mechanism of leukemogenesis and assists development of diagnostic/therapeutic strategies.


Development ◽  
1996 ◽  
Vol 122 (9) ◽  
pp. 2709-2718 ◽  
Author(s):  
P. Miskiewicz ◽  
D. Morrissey ◽  
Y. Lan ◽  
L. Raj ◽  
S. Kessler ◽  
...  

Drosophila paired, a homolog of mammalian Pax-3, is key to the coordinated regulation of segment-polarity genes during embryogenesis. The paired gene and its homologs are unusual in encoding proteins with two DNA-binding domains, a paired domain and a homeodomain. We are using an in vivo assay to dissect the functions of the domains of this type of molecule. In particular, we are interested in determining whether one or both DNA-binding activities are required for individual in vivo functions of Paired. We constructed point mutants in each domain designed to disrupt DNA binding and tested the mutants with ectopic expression assays in Drosophila embryos. Mutations in either domain abolished the normal regulation of the target genes engrailed, hedgehog, gooseberry and even-skipped, suggesting that these in vivo functions of Paired require DNA binding through both domains rather than either domain alone. However, when the two mutant proteins were placed in the same embryo, Paired function was restored, indicating that the two DNA-binding activities need not be present in the same molecule. Quantitation of this effect shows that the paired domain mutant has a dominant-negative effect consistent with the observations that Paired protein can bind DNA as a dimer.


Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 1414-1414
Author(s):  
Kyle M. Draheim ◽  
Kimberly Erdkamp ◽  
Eward Arous ◽  
Jennifer A. Calvo ◽  
Michelle A. Kelliher

Abstract LMO2 is a member of the “LIM only” protein family and required for primitive erythropoiesis and adult vasculogenesis and angiogenesis. In erythroid cells, LMO2 interacts with TAL1 and E47 and LDB1 and GATA-1, thereby forming a transcriptional complex whose target genes include EKLF, CKIT, and p4.2 (protein 4.2). LMO2 was first implicated in leukemogenesis when it was identified in chromosomal translocations t(11;14)(p13;q11) and t(7;11)(q35;p13) found in T cell acute lymphoblastic leukemia (T-ALL) patients. Ectopic expression of LMO2 in mice recapitulates the human disease, albeit at low penetrance and following a long latency. LMO2 has been shown to synergize with TAL1, yet the mechanism of oncogene cooperativity is unknown. Two models have been proposed: the first suggests that LMO2 and TAL1 synergize by forming an active transcriptional complex that induces expression of target genes such as retinaldehyde dehydrogenase 2 (RALDH2) and TALLA1 (a surface marker of T-ALL). The second model proposes that LMO2 and TAL1 sequester the E47/HEB heterodimer, resulting in inhibition of E47/HEB-mediated transcription. To distinguish between these models, we mated our Tal1 transgenic mice and our DNA binding mutant of Tal1(R188G:R189G) with Lmo2 transgenic mice. As expected, transgenic expression of Lmo2 induced disease in 23% of mice after 302 days. Similar to published studies, Tal1 and Lmo2 expression dramatically inhibited thymocyte development and induced T cell leukemia in 100% of the mice with a mean latency of 108 days. To test whether the DNA binding properties of tal1 were required to cooperate with LMO2, we mated mice expressing a DNA binding mutant of Tal1(R188G;R189G) with Lmo2 transgenic mice and found that tumors were induced with similar kinetics; 100% of mice developed disease with an average latency of 107 days. These data suggest LMO2 does not require the DNA-binding properties of Tal1 to induce leukemia in mice and support the model that LMO2 contributes to leukemia through E47/HEB sequestration and inhibition.


Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 7-7
Author(s):  
Vijay P.S. Rawat ◽  
Natalia Arseni Arseni ◽  
Vegi M. Naidu ◽  
John P. Lynch ◽  
Wolfgang Hiddemann ◽  
...  

Abstract In AML the translocation t(12;13)(p13;q12) results in the ectopic expression of the homeobox gene Cdx2 and the expression of the ETV6-CDX2 fusion. We have shown that the ectopic expression of the proto-oncogene Cdx2 and not the expression of the ETV6-CDX2 fusion is the key event in initiating myeloid leukemogenesis in a murine model of t(12;13) AML (PNAS, Rawat et. al. 2004). We now analyzed the functional relevance of the different Cdx2 domains and explored the potential of kinase inhibitors to antagonize Cdx2 induced leukemia. For this we generated different mutants, inactivating the PBX1-interacting motif (W167A-Cdx2), or deleting the N-terminal transactivation domain (Ndel-Cdx2). Expression of Cdx2 and the different mutants was induced in primary murine BM cells by retroviral gene transfer. Target genes were identified by cDNA microarray analysis. Mice transplanted with BM cells expressing Cdx2 and its W167A-Cdx2 mutant developed transplantable AML (n=14, avg. latency 90 days). In contrast, mice transplanted with the NDel-Cdx2 mutant did not show any leukemic phenotype in vivo (n=13). In order to identify gene expression signatures associated with Cdx2 induced transformation, we performed microarray analysis on highly purified normal Sca1+/lin− HSC and Sca1+/lin+ progenitor cells transduced with the leukemogenic Cdx2 compared to the non-leukemogenic NDel-Cdx2 mutant and the GFP control vector after 72h of retrovirally induced expression of the different constructs. Compared to the NDel-Cdx2 mutant and the GFP control Cdx2 up regulated genes, which are associated with self-renewal (Wint2, Hoxb3, Etv6, Abcg2,), leukemogenesis (Lmo2, Pim-2, Hoxa9) and in signal transduction pathways (e.g. MAPK family). In addition, Cdx2 transduced BM cells showed an activated Erk1/2 pathway on the protein level. Based on these results we tested whether inhibition of the MAPK pathway would impair the leukemogenic potential of Cdx2. When Cdx2 transduced BM cells were incubated with the MEK1/2 inhibitor PD98059, a 78% reduction of viable cells (n=3, p<0.03) and of the proportion of blast-like Sca1+ positive cells were observed compared to untreated cells (n=3, p<0.005) in liquid culture after 7 days. Furthermore, incubation with the MEK1/2 inhibitor PD98059 decreased the activity of Cdx2 at the level of the short-term repopulating stem cell 8-fold as assessed in the ΔCFU-S after 7 days in vitro culture (n=7, p<0.001). In contrast, incubation with the p38 specific inhibitor SB 28049 did not show any decrease in Cdx2 activity in ΔCFU-S assay, indicating that the transforming potential of Cdx2 depends on the MEK1/2 pathway, but not on the p38 pathway. These data demonstrate that the leukemogenic potential of the homeobox gene Cdx2 depends on the N-terminal activation domain. Furthermore, our data link the oncogenic capacity of the transcription factor Cdx2 to MAPK signaling, opening the possibility to counteract homeobox-associated leukemogenesis by kinase inhibitors.


1994 ◽  
Vol 14 (6) ◽  
pp. 3938-3948 ◽  
Author(s):  
Q Lu ◽  
D D Wright ◽  
M P Kamps

E2A-PBX1 is a chimeric gene formed by the t(1;19)(q23;p13.3) chromosomal translocation of pediatric pre-B-cell leukemia. The E2A-Pbx1 fusion protein contains sequences encoding the transactivation domain of E2A joined to a majority of the Pbx1 protein, which contains a novel homeodomain. Earlier, we found that expression of E2A-Pbx1 causes malignant transformation of NIH 3T3 fibroblasts and induces myeloid leukemia in mice. Here we demonstrate that the homeodomains encoded by PBX1, as well as by the highly related PBX2 and PBX3 genes, bind the DNA sequence ATCAATCAA. E2A-Pbx1 strongly activates transcription in vivo through this motif, while Pbx1 does not. This finding suggests that E2A-Pbx1 transforms cells by constitutively activating transcription of genes regulated by Pbx1 or by other members of the Pbx protein family.


1996 ◽  
Vol 16 (8) ◽  
pp. 4128-4136 ◽  
Author(s):  
Z Wu ◽  
N L Bucher ◽  
S R Farmer

The differentiation of 3T3 preadipocytes into adipocytes is accompanied by a transient induction of C/EBPbeta and C/EBPdelta expression in response to treatment of the cells with methylisobutylxanthine (MIX) and dexamethasone (DEX), respectively. In this report, we demonstrate that peroxisome proliferator-activated receptor gamma (PPARgamma) expression in 3T3-L1 preadipocytes is induced by MIX and DEX, suggesting that C/EBPbeta and C/EBPdelta may be involved in this process. Using a tetracycline-responsive expression system, we have recently shown that the conditional ectopic expression of C/EBPbeta in NIH 3T3 fibroblasts (beta2 cells) in the presence of DEX activates the synthesis of peroxisome PPARgamma mRNA. Subsequent exposure of these cells to PPAR activators stimulates their conversion into adipocytes; however, neither the expression of C/EBPbeta nor exposure to DEX alone is capable of inducing PPARgamma expression in the beta2 cell line. We find that unlike the case for 3T3 preadipocytes, C/EBPdelta is not induced by DEX in these 3T3 fibroblasts and therefore is not relaying the effect of this glucocorticoid to the PPARgamma gene. To define the role of glucocorticoids in regulating PPARgamma expression and the possible involvement of C/EBPdelta, we have established an additional set of NIH 3T3 cell lines expressing either C/EBPdelta alone (delta23 cells) or C/EBPdelta and C/EBPbeta together (beta/delta39 cells), using the tetracycline-responsive system. Culture of these cells in tetracycline-deficient medium containing DEX, MIX, insulin, and fetal bovine serum shows that the beta/delta39 cells express PPARgamma and aP2 mRNAs at levels that are almost equivalent to those observed in fully differentiated 3T3-L1 adipocytes. These levels are approximately threefold higher than their levels of expression in the beta2 cells. Despite the fact that these beta/delta39 cells produce abundant amounts of C/EBPbeta and C/EBPdelta (in the absence of tetracycline), they still require glucocorticoids to attain maximum expression of PPARgamma mRNA. Furthermore, the induction of PPARgamma mRNA by exposure of these cells to DEX occurs in the absence of ongoing protein synthesis. The delta23 cells, on the other hand, are not capable of activating PPARgamma gene expression when exposed to the same adipogenic inducers. Finally, attenuation of ectopic C/EBPbeta production at various stages during the differentiation process results in a concomitant inhibition of PPARgamma and the adipogenic program. These data strongly suggest that the induction of PPARgamma gene expression in multipotential mesenchymal stem cells (NIH 3T3 fibroblasts) is dependent on elevated levels of C/EBPbeta throughout the differentiation process, as well as an initial exposure to glucocorticoids. C/EBPdelta may function by synergizing with C/EBPbeta to enhance the level of PPARgamma expression.


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