Unknown,Transcriptomics,Genomics,Proteomics

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Gene silencing triggers Polycomb Repressive Complex 2 recruitment to CpG islands genome-wide [RNA-seq_differentiation]

ABSTRACT: Polycomb group (PcG) proteins are required for normal differentiation and development, and their activity is found deregulated in cancer. PcG proteins are involved in gene silencing, however, whether they initiate or maintain transcriptional repression is a subject of debate. Here, we show that knockout of the Polycomb repressive complex 2 (PRC2) does not lead to significant gene expression changes in mouse embryonic stem cells (mESCs), and that it is dispensable for initiating silencing of target genes during differentiation. Transcriptional inhibition in mESCs is sufficient to induce genome-wide ectopic PRC2 recruitment to endogenous PcG target genes found in other tissues. PRC2 binding analysis shows that it is restricted to nucleosome-free CpG islands (CGIs) of un-transcribed genes. Our results show that it is the transcriptional state that governs PRC2 binding, and we propose that it binds by default to non-transcribed CGI genes to maintain their silenced state and to protect cell identity. RNA-seq time-course experiments during in vitro differentiation (0h, 24h, 48h and 72h) of Mus musculus wild-type E14 and Suz12 knock-out Embryonic Stem Cells with two biological replicates per condition.

ORGANISM(S): Mus musculus

SUBMITTER: Kristian Helin

PROVIDER: E-GEOD-58017 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Publications

Gene silencing triggers polycomb repressive complex 2 recruitment to CpG islands genome wide.

Riising Eva Madi EM Comet Itys I Leblanc Benjamin B Wu Xudong X Johansen Jens Vilstrup JV Helin Kristian K

Molecular cell 20140703 3

Polycomb group (PcG) proteins are required for normal differentiation and development and are frequently deregulated in cancer. PcG proteins are involved in gene silencing; however, their role in initiation and maintenance of transcriptional repression is not well defined. Here, we show that knockout of the Polycomb repressive complex 2 (PRC2) does not lead to significant gene expression changes in mouse embryonic stem cells (mESCs) and that it is dispensable for initiating silencing of target g ...[more]

PMID: 24999238

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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.

Dataset Information

Gene silencing triggers Polycomb Repressive Complex 2 recruitment to CpG islands genome-wide [RNA-seq_differentiation]

Publications

Gene silencing triggers polycomb repressive complex 2 recruitment to CpG islands genome wide.

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