Unknown,Transcriptomics,Genomics,Proteomics

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The histone methyltransferase activity of MLL1 is dispensable for hematopoiesis and leukemogenesis

ABSTRACT: Despite correlations between histone methyltransferase (HMT) activity and gene regulation, direct evidence that HMT activity is responsible for gene activation is sparse. We address the role of the HMT activity for MLL1, a histone H3 lysine 4 (H3K4) methyltransferase critical for maintaining hematopoietic stem cells (HSCs). Here we show that the SET domain and thus HMT activity of MLL1 is dispensable for maintaining HSCs and for supporting leukemogenesis driven by the MLL-AF9 fusion oncoprotein. Upon Mll1 deletion, histone H4 lysine 16 (H4K16) acetylation was selectively depleted at MLL1 target genes in conjunction with reduced transcription. Surprisingly, inhibition of SIRT1 was sufficient to prevent the loss of H4K16 acetylation and the reduction in MLL1 target gene expression. Thus, recruited MOF activity, and not the intrinsic HMT activity of MLL1, is central for the maintenance of HSC target genes. In addition, this work reveals a role for SIRT1 in opposing MLL1 function. 11 Samples, 5 controls and 5 KOs with antibodies H3K4me1, H3K4me3, and H3K27Ac. One input Sample.

ORGANISM(S): Mus musculus

SUBMITTER: Patricia Ernst

PROVIDER: E-GEOD-56456 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:To investigate the regulatory mechanisms governing the malignant signature of different gliomas we analyzed microRNA expression profiles in human tumor samples of world health organization (WHO) grade I (benign tumors), II (low grade tumors) and IV (high grade tumors) and from primary cultures obtained from tumor samples of grade II and IV. Patients This study included tumor samples histologically verified as astrocytic gliomas obtained from patients who had undergone craniotomy for microsurgical tumor removal. According to the revised WHO classification, tumors were diagnosed as: grade I or pilocytic astrocytomas; grade II or diffuse fibrillary astrocytomas; grade IV or glioblastoma multiforme. Primary cell cultures from grade II and grade IV gliomas were also obtained and miRNA expression in these cultures were analyzed RNA extraction Total RNA, including small RNA, was isolated from tissue samples using the mirVanaTM miRNA Isolation Kit (Ambion) following the standard protocol. The quantity and quality of the purified RNA was evaluated by spectrophotometric analysis and electrophoresis on denaturing gel of acrylamide. Multiplex Real-Time Quantitative Reverse-Transcriptase Polymerase Chain Reaction (RT-PCR) The miRNAs were first converted to cDNA using Multiplex RT for TaqMan Array Human MicroRNA Panel. The RT Master mix included 100 mM each of dNTPs , 50 U/ml MultiScrabe reverse transcriptase (Applied Biosystems), 20 U/M-BM-5l RNase inhibitor (Applied Biosystems) and 10X RT Buffer. The 10 M-BM-5l reactions, including 7 M-BM-5l of RT master mix, 2 M-BM-5l of purified microRNA and 1 M-BM-5l of Multiplex RT Human primer pool (Applied Biosystem), were incubated in ice for 5 min and then in a thermal cycler for 30 min at 16M-BM-0C, 30 min at 42M-BM-0C, 5 min at 85M-BM-0C, and then hold at 4M-BM-0C. miRNA levels were normalized to the expression of small nucleolar RNAs, RNU44, RNU48 and RNU6B. All reverse transcriptase reactions, including no-template controls and RT controls, were run in duplicate. Real-time PCR was performed using a standard TaqMan PCR kit procedure on an M-bM-^@M-^\Real Time Fast 7900 HTM-bM-^@M-^] PCR System (Applied Biosystems). The 100 M-BM-5l PCR included 50 M-BM-5l RT product (before diluited 1:60) and 50 M-BM-5l TaqMan Universal PCR Master Mix (2X) (Applied Biosystems). The total volume were loaded into Card TaqMan Low Density Array Human MicroRNA Panel (Applied Biosystem) including a total of 384 human microRNAs publicated on databases www.sanger.ac.uk. The reaction cards was runned at 50M-BM-0C for 2 min and 95M-BM-0C for 10 min, followed by 40 cycles of 97M-BM-0C for 30s and 59,7M-BM-0C for 1 min. All reactions were run in triplicate. Analysis of data was performed using the SDS 2.3 software using the 2-M-bM-^HM-^FM-bM-^HM-^FCt (relative quantitative) method . The M-bM-^HM-^FCt of every miRNA was determined in relation to the endogenous control RNA U6 that was invariably expressed in all samples. The M-bM-^HM-^FM-bM-^HM-^FCt value was determined in relation to the calibrator, namely the normal brain tissue. Resulting data were grouped according to the tumor grading e selectioned using a cut-off value of 3. Results were expressed as M-bM-^@M-^\fold changeM-bM-^@M-^] over normal brain tissue. We analyzed two samples of grade I, two samples of grade II, two samples of grade IV gliomas. Four samples form norma brain were used as norma control. Primary cell cultures form grade II and grade IV samples were used for the analysis. All reverse transcriptase reactions, including no-template controls and RT controls, were run in triplicate.

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The histone methyltransferase activity of MLL1 is dispensable for hematopoiesis and leukemogenesis

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