Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.7.6 (RNA polymerase)
34,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A patient with secondary acute myelomonocytic leukemia after treatment with chronic oral etoposide (VP-16) for lung cancer is reported. The leukemic cells showed a t(9;11)(p22;q23) translocation. Southern blot analysis revealed the rearrangement of the MLL (ALL-1/HRX) gene at 11q23. Reverse transcriptase-polymerase chain reaction (RT-PCR) revealed a chimeric mRNA between the MLL gene at 11q23 and LTG9 (MLLT3/AF-9) gene at 9p22. The patient was successfully treated with a VP-16 based regimen. This case is instructive in the understanding of the leukemogenesis of VP-16-related leukemias.
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PMID:Acute myelomonocytic leukemia after treatment with chronic oral etoposide: are MLL and LTG9 genes targets for etoposide? 794 64

The SWI1/ADR6, SWI2/SNF2, SWI3, SNF5, and SNF6 gene products are all required for proper transcriptional control of many genes in the yeast Saccharomyces cerevisiae. Genetic studies indicated that these gene products might form a multiprotein SWI/SNF complex important for chromatin transitions preceding transcription from RNA polymerase II promoters. Biochemical studies identified a SWI/SNF complex containing these and at least six additional polypeptides. Here we show that the 29-kDa component of the SWI/SNF complex is identical to TFG3/TAF30/ANC1. Thus, a component of the SWI/SNF complex is also a member of the TFIIF and TFIID transcription complexes. TFG3 interacted with the SNF5 component of the SWI/SNF complex in protein interaction blots. TFG3 is significantly similar to ENL and AF-9, two proteins implicated in human acute leukemia. These results suggest that ENL and AF-9 proteins interact with the SNF5 component of the human SWI/SNF complex and raise the possibility that the SWI/SNF complex is involved in acute leukemia.
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PMID:TFG/TAF30/ANC1, a component of the yeast SWI/SNF complex that is similar to the leukemogenic proteins ENL and AF-9. 866 46

Acute leukemias arise secondary to chromosomal aberrations that cause dysfunctions in gene regulation and regulatory factors. Significant differences in morphology between acute leukemic and nonleukemic hematopoietic cells are readily observed. How morphologic changes of the nuclei of acute leukemic cells relate to the underlying functional alterations of gene expression is minimally understood. Spatial modifications in the representation and/or organization of regulatory factors may be functionally linked to perturbations of gene expression in acute leukemic cells. Using in situ immunofluorescence microscopy, we addressed the interrelationships of modifications in nuclear morphology with the intranuclear distribution of leukemia-related regulatory factors (including ALL-1, PML, and AF-9) in cells from patients with acute leukemia. We compared the localization of leukemia-associated proteins with various factors involved in gene transcription and RNA processing (e.g., RNA polymerase II and SC-35). Our findings suggest that there are leukemia-associated aberrations in mechanisms that direct regulatory factors to sites within the nucleus. This misplacement of key cognate factors may contribute to perturbations in gene expression characteristic of leukemias.
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PMID:Modified intranuclear organization of regulatory factors in human acute leukemias: reversal after treatment. 1067 14

The MLL gene in chromosome band 11q23 is frequently rearranged in acute lymphoblastic and acute myeloid leukemias. To date, more than 50 different chromosomal regions are known to participate in translocations involving 11q23, many of which affect MLL. The pathogenetically important outcome of these rearrangements is most likely the creation of a fusion gene consisting of the 5' part of the MLL gene and the 3' end of the partner gene. Although abnormalities of the MLL gene as such are generally associated with poor survival, recent data suggest that the prognostic impact varies among the different fusion genes generated. Hence, detection of the specific chimeric gene produced is important for proper prognostication and clinical decision making. We have developed a paired multiplex reverse-transcriptase polymerase chain reaction analysis to facilitate a rapid and accurate detection of the most frequent MLL fusion genes in adult and childhood acute leukemias. To increase the specificity, two sets of primers were designed for each fusion gene, and these paired primer sets were run in parallel in two separate multiplex one-step PCR reactions. Using the described protocol, we were able to amplify successfully, in one single assay, the six clinically relevant fusion genes generated by the t(4;11)(q21;q23) [MLL/AF4], t(6;11)(q27;q23) [MLL/AF6], t(9;11)(p21-22;q23) [MLL/AF9], t(10;11)(p11-13;q23) [MLL/AF10], t(11;19)(q23;p13.1) [MLL/ELL], and t(11;19)(q23; p13.3) [MLL/ENL] in cell lines, as well as in patient material.
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PMID:Paired multiplex reverse-transcriptase polymerase chain reaction (PMRT-PCR) analysis as a rapid and accurate diagnostic tool for the detection of MLL fusion genes in hematologic malignancies. 1214 6

More than 30 fusions involving the MLL gene at 11q23 have been reported in acute myeloid leukemia (AML). Some of these chimeras are rather common, such as MLL/MLLT3(AF9), but many are quite rare, with some, for example, MLL/GRAF, described only in a single case. The MLL/GRAF fusion, in which the reciprocal hybrid was not expressed, suggesting that the former transcript was the leukemogenic one, was detected in a juvenile myelomonocytic leukemia with a t(5;11)(q31;q23). Here, we report a second case--an infant acute monocytic leukemia (AML M5b)--with an MLL/GRAF fusion. By conventional G-banding, the karyotype was normal. However, Southern blot and fluorescence in situ hybridization analyses revealed that MLL was rearranged and that the 5' part of the MLL gene was inserted into 5q in the vicinity of 5q31, which harbors GRAF. Reverse-transcriptase polymerase chain reaction (PCR) showed that exon 9 of MLL was fused in-frame with exon 19 of GRAF. Extralong genomic PCR with subsequent sequence analysis demonstrated that the breakpoints occurred in intron 9 of MLL, nine base pairs (bp) downstream from exon 9, and in intron 18 of GRAF, 117 bp downstream from exon 18. A 6-bp insertion (ACACTC) of unknown origin was present at the junction. The putative MLL/GRAF fusion protein would retain the AT-hook DNA-binding domain, the DNA methyl transferase motif, the transcription repression domain of MLL, and the SH3 domain of GRAF. As expected, the reciprocal GRAF/MLL was neither expressed nor generated at the genomic level as a consequence of the ins(5;11)(q31;q23q23). On the basis of the now-reported two cases with MLL/GRAF, we conclude that this transcript--but not the reciprocal one--characterizes a rare genetic subgroup of infant AML.
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PMID:MLL/GRAF fusion in an infant acute monocytic leukemia (AML M5b) with a cytogenetically cryptic ins(5;11)(q31;q23q23). 1585 79

The fusion transcripts of MLL rearrangement [MLL(+)] in acute myeloid leukemia (AML) and their clinicohematologic correlation have not be well characterized in the previous studies. We used Southern blot analysis to screen MLL(+) in de novo AML. Reverse transcriptase-polymerase chain reaction was used to detect the common MLL fusion transcripts. cDNA panhandle PCR was used to identify infrequent or unknown MLL partner genes. MLL(+) was identified in 114 (98 adults) of 988 AML patients. MLL fusion transcripts comprised of 63 partial tandem duplication of MLL (MLL-PTD), 14 MLL-AF9, 9 MLL-AF10, 9 MLL-ELL, 8 MLL-AF6, 4 MLL-ENL and one each of MLL-AF1, MLL-AF4, MLL-MSF, MLL-LCX, MLL-LARG, MLL-SEPT6 and MLL-CBL. The frequency of MLL-PTD was 7.1% in adults and 0.9% in children (P<0.001). 11q23 abnormalities were detected in 64% of MLL/t11q23 and in none of MLL-PTD by conventional cytogenetics. There were no differences in remission rate, event-free survival and overall survival between adult MLL-PTD and MLL/t11q23 groups. Adult patients had a significantly poorer outcome than children. The present study showed that cDNA panhandle PCR can identify all rare or novel MLL partner genes. MLL-PTD was rare in childhood AML. MLL(+) adults had a poor outcome with no difference in survival between MLL-PTD and MLL/t11q23 groups.
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PMID:Characterization of fusion partner genes in 114 patients with de novo acute myeloid leukemia and MLL rearrangement. 1634 Oct 46

The increasing number of chromosomal rearrangements involving the human MLL gene, in combination with differences in clinical behavior and outcome for MLL-rearranged leukemia patients, makes it necessary to reflect on the cancer mechanism and to discuss potential therapeutic strategies. To date, 64 different translocations have been identified at the molecular level. With very few exceptions, most of the identified fusion partner genes encode proteins that display no homologies or functional equivalence. Only the most frequent fusion partners (AF4 family members, AF9, ENL, AF10 and ELL) are involved in the positive transcription elongation factor b-dependent activation cycle of RNA polymerase II. Biological functions remain to be elucidated for the other fusion partners. This minireview tries to sum up some of the available data and mechanisms identified in leukemic stem and leukemic tumor cells and link this information with the known functions of mixed lineage leukemia and certain mixed lineage leukemia fusion partners.
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PMID:Mixed lineage leukemia: roles in human malignancies and potential therapy. 2023 11

Mutations of leukemia-associated AF9/MLLT3 are implicated in neurodevelopmental diseases, such as epilepsy and ataxia, but little is known about how AF9 influences brain development and function. Analyses of mouse mutants revealed that during cortical development, AF9 is involved in the maintenance of TBR2-positive progenitors (intermediate precursor cells, IPCs) in the subventricular zone and prevents premature cell cycle exit of IPCs. Furthermore, in postmitotic neurons of the developing cortical plate, AF9 is implicated in the formation of the six-layered cerebral cortex by suppressing a TBR1-positive cell fate mainly in upper layer neurons. We show that the molecular mechanism of TBR1 suppression is based on the interaction of AF9 with DOT1L, a protein that mediates transcriptional control through methylation of histone H3 lysine 79 (H3K79). AF9 associates with the transcriptional start site of Tbr1, mediates H3K79 dimethylation of the Tbr1 gene, and interferes with the presence of RNA polymerase II at the Tbr1 transcriptional start site. AF9 expression favors cytoplasmic localization of TBR1 and its association with mitochondria. Increased expression of TBR1 in Af9 mutants is associated with increased levels of TBR1-regulated expression of NMDAR subunit Nr1. Thus, this study identified AF9 as a developmental active epigenetic modifier during the generation of cortical projection neurons.
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PMID:Af9/Mllt3 interferes with Tbr1 expression through epigenetic modification of histone H3K79 during development of the cerebral cortex. 2034 16

Recruitment of the P-TEFb kinase by HIV-1 Tat to the viral promoter triggers the phosphorylation and escape of RNA polymerase II from promoter-proximal pausing. It is unclear, however, if Tat recruits additional host factors that further stimulate HIV-1 transcription. Using a sequential affinity-purification scheme, we have identified human transcription factors/coactivators AFF4, ENL, AF9, and elongation factor ELL2 as components of the Tat-P-TEFb complex. Through the bridging functions of Tat and AFF4, P-TEFb and ELL2 combine to form a bifunctional elongation complex that greatly activates HIV-1 transcription. Without Tat, AFF4 can mediate the ELL2-P-TEFb interaction, albeit inefficiently. Tat overcomes this limitation by bringing more ELL2 to P-TEFb and stabilizing ELL2 in a process that requires active P-TEFb. The ability of Tat to enable two different classes of elongation factors to cooperate and coordinate their actions on the same polymerase enzyme explains why Tat is such a powerful activator of HIV-1 transcription.
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PMID:HIV-1 Tat and host AFF4 recruit two transcription elongation factors into a bifunctional complex for coordinated activation of HIV-1 transcription. 2047 48

MLL is involved in chromosomal rearrangements that generate fusion proteins with deregulated transcriptional activity. The mechanisms of MLL fusion protein-mediated transcriptional activation are poorly understood. Here we show MLL interacts directly with the polymerase associated factor complex (PAFc) through sequences flanking the CxxC domain. PAFc interacts with RNA polymerase II and stimulates posttranslational histone modifications. PAFc augments MLL and MLL-AF9 mediated transcriptional activation of Hoxa9. Conversely, knockdown of PAFc disrupts MLL fusion protein-mediated transcriptional activation and MLL recruitment to target loci. PAFc gene expression is downregulated during hematopoiesis and likely serves to regulate MLL function. Deletions of MLL that abolish interactions with PAFc also eliminate MLL-AF9 mediated immortalization indicating an essential function for this interaction in leukemogenesis.
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PMID:The PAF complex synergizes with MLL fusion proteins at HOX loci to promote leukemogenesis. 2067 49


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