Unknown,Transcriptomics,Genomics,Proteomics

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RNAi mediates post-transcriptional repression of gene expression in fission yeast Schizosaccharomyces pombe [Affymetrix]

ABSTRACT: RNA interference (RNAi) is a gene silencing mechanism conserved from fungi to mammals. Small interfering RNAs are products and mediators of the RNAi pathway and act as specificity factors in recruiting effector complexes. The Schizosaccharomyces pombe genome encodes one of each of the core RNAi proteins, Dicer, Argonaute and RNA-dependent RNA polymerase (dcr1, ago1, rdp1). Even though the function of RNAi in heterochromatin assembly in S. pombe is established, its role in controlling gene expression is elusive. Here, we report the identification of small RNAs mapped anti-sense to protein coding genes in fission yeast. We demonstrate that these genes are up-regulated at the protein level in RNAi mutants, while their mRNA levels are not significantly changed. We show that the repression by RNAi is not a result of heterochromatin formation. Thus, we conclude that RNAi is involved in post-transcriptional gene silencing in S. pombe. Total RNA from wild type, dcr1M-NM-^T and rpd1M-NM-^T cells; 3 biological replicates for each strain.

ORGANISM(S): Schizosaccharomyces pombe 972h-

SUBMITTER: Agata Smialowska

PROVIDER: E-GEOD-54190 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Heterochromatin plays a key role in gene repression, maintaining genome integrity and chromosome segregation. Fission yeast, Schizosaccharomyces pombe, utilizes conserved components to direct heterochromatin formation using siRNA generated by RNA interference (RNAi) to guide a histone H3 lysine 9 methyltransferase to cognate chromatin. To identify compounds that inhibit heterochromatin formation, an in vivo phenotypic screen for loss of silencing was performed. A tester strain harbouring a silent dominant selectable kanMX reporter gene within fission yeast centromeric heterochromatin was used to screen a diverse library of chemicals. HMS-I1 and HMS-I2 were identified as compounds that reproducibly increased G418 resistance due to loss of kanMX silencing, and decreased the level of repressive H3K9 methylation on centromeric repeats. The pattern of changes induced by HMS-I1 and HMS-I2 were consistent with inhibition of the histone deacetylases (HDACs) Clr3 and/or Sir2. Chemical-genetic interactions and expression profiling indicated that both HMS-I1 and HMS-I2 affect the activity of the Clr3-containing Snf2/HDAC repressor complex (SHREC). Exposure to HMS-I1 was also found to alleviate silencing of reporter genes in an Arabidopsis transgenic plant line and a mouse cell line. HMS-I2 also disrupted reporter gene silencing in Arabidopsis. In vitro assays indicate that HMS-I1 impairs the activity of human HDAC6 and HDAC10. As HMS-I1 and HMS-I2 bear no resemblance to known inhibitors of chromatin-based activities they represent potentially novel and valuable reagents for experimental and therapeutic purposes. Our findings highlight the use of in vivo chemical screening conducted in fission yeast to identify compounds that disrupt heterochromatin across plant, fungi and animal kingdoms. 16 RNA samples: 2 replicates of WT untreated (vehicle DMSO) (KE1-A, KE2-A), HMS-I1 treated (KE1-B, KE2-B), HMS-I2 treated (KE1-C, KE2-C), and 2 additional replicates of WT (KE05_wt_1, KE10_wt_2), 4 replicates of clr2M-bM-^HM-^F (KE01_2118_1, KE06_2118_2, KE03_0080_1, KE08_0080_2) and mit1M-bM-^HM-^F (KE02_1295_1, KE07_1295_2, KE04_1278_1, KE09_1278_2).

Project description:Functional centromeres are essential for proper cell division. Centromeres are established largely by epigenetic processes resulting in incorporation of the histone H3 variant CENP-A. Here, we demonstrate the direct involvement of H2B monoubiquitination, mediated by RNF20 in humans or Brl1 in Schizosaccharomyces pombe, in centromeric chromatin maintenance. Monoubiquinated H2B (H2Bub1) is needed for this maintenance, promoting noncoding transcription, centromere integrity and accurate chromosomal segregation. A transient pulse of centromeric H2Bub1 leads to RNA polymerase IIM-bM-^@M-^Smediated transcription of the centromereM-bM-^@M-^Ys central domain, coupled to decreased H3 stability. H2Bub1-deficient cells have centromere cores that, despite their intact centromeric heterochromatin barriers, exhibit characteristics of heterochromatin, such as silencing histone modifications, reduced nucleosome turnover and reduced levels of transcription. In the H2Bub1-deficient cells, centromere functionality is hampered, thus resulting in unequal chromosome segregation. Therefore, centromeric H2Bub1 is essential for maintaining active centromeric chromatin. ChIP: In total 17 samples; 15 ChIP DNA files (7 different conditions) 2 Input files. Cnp1_WT_input.bar (antibody against Cnp1 in strains Hu303, Hu29 (WT) (Cnp1_Hu303.CEL, AS_10.CEL) vs input (JW_1.CEL, JW_2_2.CEL)); Cnp1_Hu2640_WT.bar (antibody against Cnp1 in strain Hu2640 (htb1K119R) (Cnp1_Hu2640_A.CEL, Cnp1_Hu2640_B.CEL) vs strains Hu303, Hu29 (WT) (Cnp1_Hu303.CEL, AS_10.CEL)); Cnp1_Hu2640_input.bar (antibody against Cnp1 in strain Hu2640 (htb1K119R) (Cnp1_Hu2640_A.CEL, Cnp1_Hu2640_B.CEL) vs input (JW_1.CEL, JW_2_2.CEL)); H2Bub1_Hu303_input.bar (antibody against H2Bub1 in strain Hu303 (WT) (H2Bub1_Hu303_A.CEL, H2Bub1_Hu303_B.CEL) vs input (JW_1.CEL, JW_2_2.CEL)); H3_WT_input.bar (antibody against H3 in strains Hu303, Hu29 (WT) (H3_Hu303.CEL, As_12.CEL) vs input (JW_1.CEL, JW_2_2.CEL); H3_Hu2640_WT.bar (antibody against H3 in strain Hu2640 (htb1K119R) (H3_Hu2640_A.CEL, H3_Hu2640_B.CEL, H3_Hu2640_C.CEL) vs strains Hu303, Hu29 (WT) (H3_Hu303.CEL, AS_12.CEL)); H3_Hu2640_input.bar (antibody against H3 in strain Hu2640 (htb1K119R) (H3_Hu2640_A.CEL, H3_Hu2640_B.CEL, H3_Hu2640_C.CEL) vs input (JW_1.CEL, JW_2_2.CEL)); H3K9me2_Hu303_input.bar (antibody against H3K9me2 in strains Hu303, Hu29 (WT) (H3K9me2_Hu303.CEL, AS_6.CEL) vs input (JW_1.CEL, JW_2_2.CEL)); H3k9me2_Hu2640_Hu303.bar (antibody against H3K9me2 in strain Hu2640 (htb1K119R) (H3K9me2_Hu2640_A.CEL, H3K9me2_Hu2640_B.CEL) vs strain Hu303, Hu29 (WT) (H3K9me2_Hu303.CEL, AS_6.CEL)); H3K9me2_Hu2640_input.bar (antibody against H3K9me2 in strain Hu2640 (htb1K119R) (H3K9me2_Hu2640_A.CEL, H3K9me2_Hu2640_B.CEL) vs input (JW_1.CEL, JW_2_2.CEL)). RNA: 4 RNA samples: 2 replicates of WT RNA (RNA_Hu303_A.CEL, RNA_Hu303_B.CEL) and 2 replicates of htb1-K119R RNA (RNA_Hu2640_A.CEL, RNA_Hu2640_B.CEL).

Project description:Specialized chromatin containing CENP-A nucleosomes instead of H3 nucleosomes is found at all centromeres. However, the mechanisms that specify the locations at which CENP-A chromatin is assembled remain elusive in organisms with regional, epigenetically regulated centromeres. It is known that normal centromeric DNA is transcribed in several systems including the fission yeast, Schizosaccharomyces pombe. Here, we show that factors which preserve stable histone H3 chromatin during transcription also play a role in preventing promiscuous CENP-A(Cnp1) deposition in fission yeast. Mutations in the histone chaperone FACT impair the maintenance of H3 chromatin on transcribed regions and promote widespread CENP-A(Cnp1) incorporation at non-centromeric sites. FACT has little or no effect on CENP-A(Cnp1) assembly at endogenous centromeres where CENP-A(Cnp1) is normally assembled. In contrast, Clr6 complex II (Clr6-CII; equivalent to Rpd3S) histone deacetylase function has a more subtle impact on the stability of transcribed H3 chromatin and acts to prevent the ectopic accumulation of CENP-A(Cnp1) at specific loci, including subtelomeric regions, where CENP-A(Cnp1) is preferentially assembled. Moreover, defective Clr6-CII function allows the de novo assembly of CENP-A(Cnp1) chromatin on centromeric DNA, bypassing the normal requirement for heterochromatin. Thus, our analyses show that alterations in the process of chromatin assembly during transcription can destabilize H3 nucleosomes and thereby allow CENP-A(Cnp1) to assemble in its place. We propose that normal centromeres provide a specific chromatin context that limits reassembly of H3 chromatin during transcription and thereby promotes the establishment of CENP-A(Cnp1) chromatin and associated kinetochores. These findings have important implications for genetic and epigenetic processes involved in centromere specification. In total, 24 samples: 22 ChIP DNA files (10 different conditions), 2 Input files.

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RNAi mediates post-transcriptional repression of gene expression in fission yeast Schizosaccharomyces pombe [Affymetrix]

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