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Topoisomerase 3β Interacts with RNAi Machinery to Promote Heterochromatin Formation and Transcriptional Silencing in Drosophila [ChIP-Seq]

ABSTRACT: Topoisomerases solve topological problems during DNA metabolism, but whether they participate in RNA metabolism remains unclear. Top3b represents a family of topoisomerases carrying activities for both DNA and RNA. Here we show that in Drosophila, Top3b interacts biochemically and genetically with the RNAi-induced silencing complex (RISC) containing AGO2, p68 RNA helicase, and FMRP. Top3b and RISC mutants are similarly defective in heterochromatin formation and transcriptional silencing by position-effect variegation assay. Moreover, both Top3b and AGO2 mutants exhibit reduced levels of heterochromatin protein HP1 in pericentric heterochromatin. Furthermore, expression of several genes and transposable elements in heterochromatin is increased in the Top3b mutant. Notably, Top3b mutants defective in either RNA binding or catalytic activity are deficient in promoting HP1 recruitment and silencing of transposable elements. Our data suggest that Top3b may act as an RNA topoisomerase in siRNA-guided heterochromatin formation and transcriptional silencing.

ORGANISM(S): Drosophila melanogaster

PROVIDER: GSE119777 | GEO | 2018/09/12

REPOSITORIES: GEO

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Topoisomerase 3β Interacts with RNAi Machinery to Promote Heterochromatin Formation and Transcriptional Silencing in Drosophila [RNA-Seq]

Project description:Topoisomerases solve topological problems during DNA metabolism, but whether they participate in RNA metabolism remains unclear. Top3b represents a family of topoisomerases carrying activities for both DNA and RNA. Here we show that in Drosophila, Top3b interacts biochemically and genetically with the RNAi-induced silencing complex (RISC) containing AGO2, p68 RNA helicase, and FMRP. Top3b and RISC mutants are similarly defective in heterochromatin formation and transcriptional silencing by position-effect variegation assay. Moreover, both Top3b and AGO2 mutants exhibit reduced levels of heterochromatin protein HP1 in pericentric heterochromatin. Furthermore, expression of several genes and transposable elements in heterochromatin is increased in the Top3b mutant. Notably, Top3b mutants defective in either RNA binding or catalytic activity are deficient in promoting HP1 recruitment and silencing of transposable elements. Our data suggest that Top3b may act as an RNA topoisomerase in siRNA-guided heterochromatin formation and transcriptional silencing.

2018-09-12 | GSE119626 | GEO

Topoisomerase 3B Interacts with RNAi Machinery to Promote Heterochromatin Formation and Transcriptional Silencing

Project description:Topoisomerases solve topological problems during DNA metabolism, but whether they participate in RNA metabolism remains unclear. Top3b represents a new family of topoisomerases carrying activities for both DNA and RNA. Here we show that in Drosophila, Top3b interacts biochemically and genetically with the RNAi-induced silencing complex (RISC) containing AGO2, p68 RNA helicase, and FMRP. Top3b and RISC mutants are defective in heterochromatin formation and transcriptional silencing by position-effect variegation assay; and this defect is suppressed in their double mutants. Moreover, both Top3b and AGO2 single mutants exhibit reduced heterochromatin protein HP1 in pericentric heterochromatin; and this reduction is also suppressed in their double mutant. Furthermore, expression of several genes and transposable elements (TEs) in heterochromatin is increased in the Top3b mutant. Notably, Top3b mutants defective in either RNA binding or catalytic activity are deficient in promoting HP1 recruitment and silencing of TEs. Our data suggest that Top3b acts as an RNA topoisomerase in siRNA-guided heterochromatin formation and transcriptional silencing. Grant title: An RNA topoisomerase complex interacts with Fragile X syndrome protein to promote neurodevelopment and maintain normal life-span. Grant ID: AG000689-08. Source: NIA/NIH

2018-08-29 | GSE119185 | GEO

Casein kinase 1 and 2 phosphorylate a conserved cluster of Argonaute to control microRNA functionCasein kinase 1 and 2 phosphorylate a conserved cluster of Argonaute to control microRNA function

Project description:MicroRNAs (miRNAs) together with Argonaute (AGO) proteins form the core of the RNA-induced silencing complex (RISC) to regulate gene expression of their target RNAs post-transcriptionally. Argonaute proteins are subjected to intensive regulation via various post-translational modifications that can affect their stability, silencing efficacy and specificity for targeted gene regulation. We report here that in C. elegans, two conserved serine/threonine kinases - Casein Kinase 1 alpha 1 (CK1A1) and Casein Kinase 2 (CK2) - regulate a highly conserved phosphorylation cluster of 4 Serine residues (S988:S998) on the miRNA-specific AGO protein ALG-1. We show that CK1A1 phosphorylates ALG-1 at sites S992 and S995, while CK2 phosphorylates ALG-1 at sites S988 and S998. Furthermore, we demonstrate that phospho-mimicking mutants of the entire S988:S998 cluster rescue the various developmental defects observed upon depleting CK1A1 and CK2. In humans, we show that CK1A1 also acts as a priming kinase of this cluster on AGO2. Altogether, our data suggest that phosphorylation of AGO within the cluster by CK1A1 and CK2 is required for efficient miRISC-target RNA binding and silencing

2023-09-13 | PXD044139 | Pride

HP1 controls genomic targeting of four novel heterochromatin proteins in Drosophila

Project description:Heterochromatin is important for the maintenance of genome stability and regulation of gene expression, yet our knowledge of heterochromatin structure and function is incomplete. We identified four novel Drosophila heterochromatin proteins. Three of these proteins (HP3, HP4, and HP5) interact directly with HP1, while HP6 in turn binds to each of these three proteins. Immunofluorescence microscopy and genome-wide mapping of in vivo binding sites shows that all four proteins are components of heterochromatin. Depletion of HP1 causes redistribution of all four proteins, indicating that HP1 is essential for their heterochromatic targeting. Finally, mutants of HP4 and HP5 are dominant suppressors of position effect variegation, demonstrating their importance in heterochromatic gene silencing. These results indicate that HP1 acts as a docking platform for several mediator proteins that contribute to heterochromatin function. Keywords: DamID knock-down

2007-02-02 | GSE6411 | GEO

A dual-activity topoisomerase complex promotes both transcriptional activation and repression in response to starvation

Project description:Topoisomerases are required to release topological stress generated by RNA polymerase II (RNAPII) during transcription. Here we show that in response to starvation, the complex of topoisomerase 3b (TOP3B) and TDRD3 can promote transcriptional activation or repression. Human HCT116 cells individually inactivated for TOP3B, TDRD3, or TOP3B topoisomerase activity, exhibit similarly disrupted transcription for both starvation-activated genes (SAGs) and starvation-repressed genes (SRGs). Responding to starvation, both TOP3B-TDRD3 and the elongating form of RNAPII exhibit concomitantly increased binding to TOP3B-dependent SAGs, at binding sites that overlap. Strikingly, TOP3B inactivation decreases the binding of elongating RNAPII to TOP3B-dependent SAGs while increased it to SRGs. Furthermore, TOP3B-ablated cells display reduced transcription of several autophagy-associated genes and autophagy per se. Our data suggest that TOP3B-TDRD3 can promote both transcriptional activation and repression by regulating RNAPII distribution. In addition, the findings that it can facilitate autophagy may account for the shortened lifespan of Top3b-KO mice.

2023-02-01 | GSE214322 | GEO

PARN mediates 3'-end trimming of Argonaute-cleaved precursor microRNAs

Project description:microRNAs (miRNAs) are typically generated as ~22-nucleotide double-stranded RNAs via processing of precursor hairpins by the RNase III enzyme Dicer, after which they are loaded into Argonaute (Ago) proteins to form RNA-induced silencing complex (RISC). However, the biogenesis of miR-451, an erythropoietic miRNA conserved in vertebrates, does not require Dicer processing. Instead, the short pre-miR-451 precursor hairpin is directly loaded into Ago, followed by cleavage of the 3' arm and trimming of the 3' end to the mature length by PARN. Here we show the in vivo activity of miR-430 Ago2-hairpin, a canonical microRNA engineered to fit the structure of miR-451 and hence become Ago2-dependent. Moreover, we test a modified miR-430 Ago2-haipin with 3x phoshorothioate bonds that impairs trimmng. Surprisingly, our data show that trimming of Ago-cleaved pre-miRNAs is not essential for target silencing, indicating that RISC is functional with miRNAs longer than 22-nucleotides. Rescue of MZdicer zebrafish mutant with the injection of trimmable and nontrimmable miR-430 Ago2 hairpins: Transcriptome of wild type, MZdicer mutant, and MZdicer mutant micoinjected with miR-430 duplex, miR-430 (Ago2-haripin), miR-430 (Ago2-haripin 3xPhosphorothioate)

2013-11-13 | E-GEOD-51036 | biostudies-arrayexpress

Uncoupling the distinct functions of HP1 proteins during heterochromatin establishment and maintenance

Project description:H3K9 methylation (H3K9me) marks transcriptionally silent genomic regions called heterochromatin. A conserved class of HP1 proteins are critically required to establish and maintain heterochromatin. HP1 proteins bind to H3K9me, recruit factors that promote heterochromatin formation, and oligomerize to form phase-separated condensates. We do not understand how HP1 protein binding to heterochromatin establishes and maintains transcriptional silencing. Here, we demonstrate that the S.pombe HP1 homolog, Swi6, can be completely bypassed to establish silencing at ectopic and endogenous loci when an H3K4 methyltransferase, Set1 and an H3K14 acetyltransferase, Mst2 are deleted. Deleting Set1 and Mst2 enhances Clr4 enzymatic activity, leading to higher H3K9me levels and increased spreading. In contrast, Swi6 and its capacity to oligomerize were indispensable during epigenetic maintenance. Our results demonstrate the role of HP1 proteins in regulating histone modification crosstalk during establishment and identifies a genetically separable function in maintaining epigenetic memory.

2023-09-26 | GSE244017 | GEO

The establishment of HP1-independent heterochromatin reveals an essential role for HP1 proteins in maintaining epigenetic memory.

2023-05-24 | GSE233333 | GEO

The establishment of HP1-independent heterochromatin reveals an essential role for HP1 proteins in maintaining epigenetic memory

2023-05-10 | GSE231618 | GEO

Effect of aging and dFOXO knockout on small RNA in Ago1 and Ago2 RNA-induced silencing complexes

Project description:To examine the effect of loss of dFOXO on Ago1 and Ago2 RISC loading in aging animals, we sequenced RNA immunoprecipitated from Ago1 and Ago2 RISC collected from whole wildtype (wDah) and dFOXO-null (dfoxoΔ94) flies at young (5 days) and old (35 days) age. dFOXO is a transcription factor that regulates Ago1 and Ago2 as well as lifespan.

2022-09-04 | GSE212492 | GEO

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