Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
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Chromosomal translocations in acute leukemia that affect the AML-1/CBFbeta transcription factor complex create dominant inhibitory proteins. However, the mechanisms by which these proteins act remain obscure. Here we demonstrate that the multidrug resistance 1 (MDR-1) promoter is a target for AML/ETO transcriptional repression. This repression is of basal, not activated, expression from the MDR-1 promoter and thus represents a new mechanism for AML/ETO function. We have defined two domains in AML/ETO that are required for repression of basal transcription from the MDR-1 promoter: a hydrophobic heptad repeat (HHR) motif and a conserved zinc finger (ZnF) domain termed the MYND domain. The HHR mediates formation of AML/ETO homodimers and AML/ETO-ETO heterodimers. Single serine substitutions at conserved cysteine residues within the predicted ZnFs also abrogate transcriptional repression. Finally, we observe that AML/ETO can also inhibit Ets-1 activation of the MDR-1 promoter, indicating that AML/ETO can disrupt both basal and Ets-1-dependent transcription. The fortuitous inhibition of MDR-1 expression in t(8;21)-containing leukemias may contribute to the favorable response of these patients to chemotherapeutic drugs.
Mol Cell Biol 1998 Jun
PMID:The MYND motif is required for repression of basal transcription from the multidrug resistance 1 promoter by the t(8;21) fusion protein. 958 1

Myeloperoxidase (MPO), an iron-containing heme protein localized in the azurophilic granules of neutrophil granulocytes and in the lysosomes of monocytes, is involved in the killing of several micro-organisms and foreign cells, including bacteria, fungi, viruses, red cells, and malignant and nonmalignant nucleated cells. Despite the primary role of the oxygen-dependent MPO system in the destruction of certain phagocytosed microbes, subjects with total or partial MPO deficiency generally do not have an increased frequency of infections, probably because other MPO-independent mechanism(s) for microbicidal activity compensate for the lack of MPO. Infectious diseases, especially with species of Candida, have been observed predominantly in MPO-deficient patients who also have diabetes mellitus, but the frequency of such cases is very low, less than 5% of reported MPO-deficient subjects. Evidence from a number of investigators indicates that individuals with total MPO deficiency show a high incidence of malignant tumors. Since MPO-deficient PMNs exhibit in vitro a depressed lytic action against malignant human cells, it can be speculated that the neutrophil MPO system plays a central role in the tumor surveillance of the host. However, any definitive conclusion on the association between MPO deficiency and the occurrence of cancers needs to be confirmed in further clinical studies. Clinical manifestations of this disorder depend on the nature of the defect; an acquired abnormality associated with other hematological or nonhematological diseases has been occasionally described, but the primary deficiency is the form more commonly reported. Another area of interest pertinent to MPO expression is related to the use of anti-MPO monoclonal antibodies for the lineage assignment of acute leukemic cells, the definition of FAB MO acute myeloid leukemia, the identification of biphenotypic acute leukemias, and their distinction from acute leukemia with minimal phenotypic deviation. The advantage of MPO monoclonal antibodies over the MPO cytochemical assay relies in the ability of the former method to recognize the enzymatically inactive precursor forms of MPO.
J Mol Med (Berl) 1998 Sep
PMID:Clinical manifestation of myeloperoxidase deficiency. 976 45

tal-1 (T-cell acute leukemia-1; also known as SCL) and tal-2 genes belong to a family of basic helix-loop-helix transcription factors and were originally isolated from the breakpoints of chromosomal translocations in human T-cell leukemia cell lines. tal-1 is expressed not only in hematopoietic cells but also in several endothelial structures and the central nervous system during development. On the other hand, the detailed function and the sites of expression of tal-2 have remained obscure. We cloned the tal-2 cDNA from a mouse embryonic cDNA library and examined its expression pattern in the mouse, comparing with that of tal-1. In situ analyses revealed that tal-2 transcripts are detected at embryonic day 12.5 in the following regions; 1) the diencephalon-the zona limitans intrathalamica and the pretectum, 2) the mesencephalon-the tectum, and the anterior and posterior tegmentum, 3) the metencephalon-the isthmus and the anterior pons. In the diencephalon and the mesencephalon, the expression sites of tal-2 gene were similar to those of tal-1, and its expression was stronger than that of tal-1. In the metencephalon, tal-2 expression was observed in the anterior pons, whereas tal-1 transcripts were detected in the entire pons, and showed stronger expression than tal-2. The tal-2 messages were barely detectable in the brain at birth. These results suggest that tal-1 and tal-2 are involved in the development of specific areas of the central nervous system.
Brain Res Mol Brain Res 1999 Feb 05
PMID:The leukemic oncogene tal-2 is expressed in the developing mouse brain. 993 88

Background: The Philadelphia chromosome (Ph), t(9;22)(q34;q11), is detected by karyotyping in a minority of patients with acute leukemia. Ph results in fusion of the c-abl oncogene on chromosome 9 with the breakpoint cluster region BCR gene on chromosome 22. The purpose of this study was to compare reverse trascriptase-polymerase chain reaction (RT-PCR) for BCR/abl fusion to cytogenetic methods for Ph detection in patients with acute leukemia. Methods and Results: Peripheral blood and bone marrow samples from cases of adult acute myelogenous leukemia (AML) and acute lymphoblastic leukemia (ALL) were examined for Ph by RT-PCR, karyotyping, and fluorescence in situ hybridization (FISH). Using total cellular RNA and a single primer pair, cDNA was transcribed, amplified, electorphoresed, and probed for BCR/abl fusion. Patient cells and SUPB15 and K562 cell lines were used as breakpoint controls. Karyotyping was done by standard Giemsa banding. FISH was performed on bone marrow smears using digxigenin-labeled DNA probes for major and minor bcr breakpoints (corresponding to involvement of major bcr exons 2/3 and minor bcr exon 1, respectively) and biotin-labeled DNA probes for abl. Rhodamine-conjugated antidigoxigenin and fluorescein-conjugated avidin yielded red and green fluorescent signals, respectively. A total of 32 samples from patients with AML were studied, 20 from patients with de novo or relapsed AML and 12 from patients in remission. Five of 32 cases of AML (16%) were RT-PCR+/Ph+ all with major bcr breakpoints between exons 3 and 4. One of the 32 cases (3%) was RT-PCR+/Ph+; this case was the only positive remission sample. Of the four T-PCR+/Ph- cases, one showed t(2;17), one showed t(9;11), and two had a normal karyotype. FISH was done in three RT-PCR+ cases, yielding positive results with the major probe in two. A total of 22 samples from patients with ALL were studies, 15 from patients with de novo or relapsed ALL and seven from patient remission. Seven of 22 cases of ALL (32%) were RT-PCR+, four with major-bcr breakpoints between exons 3 and 4, and three with breakpoints in the minor-bcr. Two of the 22 (9%) cases were RT-PCR+/Ph+. Of the five RT-PCR+/Ph- cases, two showed a 22q- but lacked the typical Ph break on chromosome 9, 1 showed a 12p-, and two had a normal karyotype. FISH was performed in four RT-PCR+ cases, yielding positive results with the major probe in two cases and with the minor probe in two cases. Conclusions: RT-PCR is more sensitive than karyotyping, detecting masked Ph or translocations not found by cytogenetic analysis. FISH is a helpful adjunctive test when used to confirm BCR/abl fusion in RT-PCR+/Ph- cases.
Mol Diagn 1996 Dec
PMID:Detection of BCRabl in Acute Leukemia by Molecular and Cytogenetic Methods. 1046 77

One of the most common chromosomal abnormalities in acute leukemia is a reciprocal translocation involving the HRX gene (also called MLL, ALL-1, or HTRX) at chromosomal locus 11q23, resulting in the formation of HRX fusion proteins. Using the yeast two-hybrid system and human cell culture coimmunoprecipitation experiments, we show here that HRX proteins interact directly with the GADD34 protein. We have found that transfected cells overexpressing GADD34 display a significant increase in apoptosis after treatment with ionizing radiation, indicating that GADD34 expression not only correlates with apoptosis but also can enhance apoptosis. The amino-terminal third of the GADD34 protein was necessary for this observed increase in apoptosis. Furthermore, coexpression of three different HRX fusion proteins (HRX-ENL, HRX-AF9, and HRX-ELL) had an anti-apoptotic effect, abrogating GADD34-induced apoptosis. In contrast, expression of wild-type HRX gave rise to an increase in apoptosis. The difference observed here between wild-type HRX and the leukemic HRX fusion proteins suggests that inhibition of GADD34-mediated apoptosis may be important to leukemogenesis. We also show here that GADD34 binds the human SNF5/INI1 protein, a member of the SNF/SWI complex that can remodel chromatin and activate transcription. These studies demonstrate, for the first time, a gain of function for leukemic HRX fusion proteins compared to wild-type protein. We propose that the role of HRX fusion proteins as negative regulators of post-DNA-damage-induced apoptosis is important to leukemia progression.
Mol Cell Biol 1999 Oct
PMID:Leukemic HRX fusion proteins inhibit GADD34-induced apoptosis and associate with the GADD34 and hSNF5/INI1 proteins. 1049 Jun 42

The Philadelphia chromosome is present in a heterogeneous group of leukemias. It is most commonly associated with chronic myelogenous leukemia (CML) and B-lineage acute lymphoblastic leukemia (ALL) being found in more than 95% and 15-25% of cases respectively. We undertook a study to determine the morphologic, phenotypic and molecular diversity of Philadelphia positive de novo acute leukemia patients seen at our institution over the past 3 1/2 years. Twenty-one patients with de novo acute leukemia were found to have the Philadelphia chromosome by cytogenetic studies. They consisted of 3 patients with acute myelogenous leukemia (AML), 1 biphenotypic leukemia and 17 ALL patients. Of the patients with ALL, 16 were of B-lineage while 1 had a T-cell phenotype. Ten patients expressed the p210 BCR-ABL transcript alone and 10 expressed only the p190 BCR-ABL transcript. One patient had co-expression of p190 and p210 b3a2 BCR-ABL transcripts. Thus the Philadelphia chromosome can be found in a diverse cohort of morphologic and immunologic subtypes of de novo acute leukemia reflecting the heterogeneity of lineage involvement in this disease.
Int J Mol Med 1999 Dec
PMID:Molecular and phenotypic spectrum of de novo Philadelphia positive acute leukemia. 1056 81

AML1 is one of the most frequently mutated genes associated with human acute leukemia and encodes the DNA-binding subunit of the heterodimering transcriptional factor complex, core-binding factor (CBF) (or polyoma enhancer binding protein 2 [PEBP2]). A null mutation in either AML1 or its dimerizing partner, CBFbeta, results in embryonic lethality secondary to a complete block in fetal liver hematopoiesis, indicating an essential role of this transcription complex in the development of definitive hematopoiesis. The hematopoietic phenotype that results from the loss of AML1 can be replicated in vitro with a two-step culture system of murine embryonic stem (ES) cells. Using this experimental system, we now demonstrate that this hematopoietic defect can be rescued by expressing the PEBP2alphaB1 (AML1b) isoform under the endogenous AML1-regulatory sequences through a knock-in (targeted insertion) approach. Moreover, we demonstrate that the rescued AML1(-/-) ES cell clones contribute to lymphohematopoiesis within the context of chimeric animals. Rescue requires the transcription activation domain of AML1 but does not require the C-terminal VWRPY motif, which is conserved in all AML1 family members and has been shown to interact with the transcriptional corepressor, Groucho/transducin-like Enhancer of split. Taken together, these data provide compelling evidence that the phenotype seen in AML1-deficient mice is due solely to the loss of transcriptionally active AML1.
Mol Cell Biol 2000 Jan
PMID:Biological characteristics of the leukemia-associated transcriptional factor AML1 disclosed by hematopoietic rescue of AML1-deficient embryonic stem cells by using a knock-in strategy. 1059 34

TEL is a member of the ETS family of transcription factors that interacts with the mSin3 and SMRT corepressors to regulate transcription. TEL is biallelically disrupted in acute leukemia, and loss of heterozygosity at the TEL locus has been observed in various cancers. Here we show that expression of TEL in Ras-transformed NIH 3T3 cells inhibits cell growth in soft agar and in normal cultures. Unexpectedly, cells expressing both Ras and TEL grew as aggregates. To begin to explain the morphology of Ras-plus TEL-expressing cells, we demonstrated that the endogenous matrix metalloproteinase stromelysin-1 was repressed by TEL. TEL bound sequences in the stromelysin-1 promoter and repressed the promoter in transient-expression assays, suggesting that it is a direct target for TEL-mediated regulation. Mutants of TEL that removed a binding site for the mSin3A corepressor but retained the ETS domain failed to repress stromelysin-1. When BB-94, a matrix metalloproteinase inhibitor, was added to the culture medium of Ras-expressing cells, it caused a cell aggregation phenotype similar to that caused by TEL expression. In addition, TEL inhibited the invasiveness of Ras-transformed cells in vitro and in vivo. Our results suggest that TEL acts as a tumor suppressor, in part, by transcriptional repression of stromelysin-1.
Mol Cell Biol 2000 Aug
PMID:TEL, a putative tumor suppressor, modulates cell growth and cell morphology of ras-transformed cells while repressing the transcription of stromelysin-1. 1091 66

HTLV-1 is the etiologic agent for adult T-cell leukemia/lymphoma (ATL) and HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP), where viral replication and transformation are largely dependent upon modification of regulatory and host cell cycle proteins. The mechanism of HTLV-1 transformation appears to be distinct from that of many known chronic or acute leukemia viruses and is related to the viral activator Tax. Here we show that cyclin E, can associate tightly with the coactivator p300 and Pol II complex in HTLV-1 infected cells. The cyclin E associated complex is kinase active and phosphorylates the carboxy terminal domain of RNA Pol II. More importantly, p21/Waf1, a well-known cdk inhibitor at the G1/S border, inhibits transcription of HTLV-1 in both transfections and in in vitro transcription assays. Finally, specific cdk chemical inhibitors, functionally similar to cellular cdkIs, such as p21/Waf1 which inhibits cyclin E/cdk2 activity, also inhibit transcription of the HTLV-1 promoter. In particular, Purvalanol A, with an IC50 of 0.035 microm inhibits activated, but not basal transcription, as well as HTLV-1 infected cells. Collectively, the role of cyclin E/cdk2 in HTLV-1 infected cells and its involvement in RNA Pol II phosphorylation is discussed.
Mol Cell Biochem 2002 Aug
PMID:Inhibition of HTLV-1 transcription by cyclin dependent kinase inhibitors. 1223 81

In this paper are presented four cases, with unusual chromosomal abnormalities, identified at the first presentation, among over 100 patients with myeloid and lymphoid acute and chronic leukemias cytogenetically investigated. The complexity and nature of cytogenetic abnormalities was in direct relationship with the disease evolution. The first case, a 22 years old man with acute lymphoblastic leukemia type L3, exhibited many structural changes in bone marrow cells with diploid number of chromosomes: del(3)(q26); del (5)(p13); t(8;14) (q24;q32); del(9)(p11q11);inv(15)(p12qter). The second case, a 62 years old woman, diagnosed as poorly differentiated acute leukemia, refractory to treatment, showed hiperdiploidy (48-54 chromosomes) and 3-4 markers derived from chromosomes 5 and 12. The third case, a young man of 27 years old, diagnosed as acute myeloid leukemia, apart of Philadelphia chromosome, presented trisomy 16, both in diploid and aneuploid cells. None of these three patients did respond to any medical therapy. Their rapid death was a powerful proof of the correlation between the complexity of genome changes and disease aggressiveness. In the fourth case, a constitutional translocation t(3;5)(q26.3;q21) identified in a 72 years old woman with essential thrombocythemia, appeared not to be involved in the etiology of the disease. In this case, the treatment with hydroxyurea was successful and the disease evolution was favourable. In conclusion, we appreciate that in the three cases of myeloid and lymphoid leukemias it was a direct relationship between the complexity of genomic changes and the aggressiveness of the disease.
J Cell Mol Med
PMID:Relationship between chromosomal changes complexity and disease aggressiveness in myeloid and lymphoid disorders. 1241 55


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