Project description:Drosophila Piwi-family proteins have been implicated in transposon control. Here, we examine piwi-interacting RNAs (piRNAs) associated with each Drosophila Piwi protein and find that Piwi and Aubergine bind RNAs that are predominantly antisense to transposons, whereas Ago3 complexes contain predominantly sense piRNAs. As in mammals, the majority of Drosophila piRNAs are derived from discrete genomic loci. These loci comprise mainly defective transposon sequences, and some have previously been identified as master regulators of transposon activity. Our data suggest that heterochromatic piRNA loci interact with potentially active, euchromatic transposons to form an adaptive system for transposon control. Complementary relationships between sense and antisense piRNA populations suggest an amplification loop wherein each piRNA-directed cleavage event generates the 5’ end of a new piRNA. Thus, sense piRNAs, formed following cleavage of transposon mRNAs, may enhance production of antisense piRNAs, complementary to active elements, by directing cleavage of transcripts from master control loci. Keywords: small RNA libraries from Drosophila ovaries small RNAs (23-29nt) were isolated from total ovarian RNA or from immunopreciptated Piwi/Aubergine/Ago3 complexes. cDNA libraries were constructed after Pfeffer et al. 2005 (Nat. Methods) and sequenced at 454 Life Sciences. The used strain is OregonR. Only sequences matching the Release5 genome assembly (www.fruitfly.org) are considered.
Project description:We have found that oncogenic Ras combined with loss of the Hippo tumour-suppressor pathway reactivates a primary piRNA pathway in Drosophila somatic cells, coincident with oncogenic transformation. In these cells, Piwi becomes loaded with piRNAs derived from generative loci, which are normally restricted to either the germline or the somatic follicle cells. Negating the pathway leads to increases in the expression of a wide variety of transposons and also to altered expression of some protein coding genes. This correlates with a reduction in the proliferation of the transformed cells in culture, suggesting that at least in this context, the piRNA pathway may play a functional role in cancer. Small RNAs cloned from whole cells, piwi-bound small RNAs and long RNA-Seq were performed in wts-RNAi;RasV12 cells to identify piRNAs and gene expression and compared to RasV12 cells, somatic OSS cells, and germline UAS-wts-RNAi;UAS-RasV12 control ovaries. After knock-down of several components of the piRNA machinery in WRR-1 cells (piwi, zuchini, armitage, aubergine, argonaute3) and GFP and/or dsRED control knock-downs, small RNAs were cloned and gene expression profiles (RNA-Seq) were established.
Project description:We have found that oncogenic Ras combined with loss of the Hippo tumour-suppressor pathway reactivates a primary piRNA pathway in Drosophila somatic cells, coincident with oncogenic transformation. In these cells, Piwi becomes loaded with piRNAs derived from generative loci, which are normally restricted to either the germline or the somatic follicle cells. Negating the pathway leads to increases in the expression of a wide variety of transposons and also to altered expression of some protein coding genes. This correlates with a reduction in the proliferation of the transformed cells in culture, suggesting that at least in this context, the piRNA pathway may play a functional role in cancer. Small RNAs cloned from whole cells, Piwi-bound small RNAs and long RNA-Seq were performed in wts-RNAi;RasV12 cells to identify piRNAs and gene expression changes compared to RasV12 cells, somatic OSS cells, and germline UAS-wts-RNAi;UAS-RasV12 control ovaries. After knock-down of components of the piRNA machinery in WRR-1 cells ([piwi, zuchini, armitage, aubergine, argonaute3) and GFP and/or dsRED control knock-downs, small RNAs were cloned and gene expression (RNA-Seq) profiles were established.
Project description:Drosophila Piwi-family proteins have been implicated in transposon control. Here, we examine piwi-interacting RNAs (piRNAs) associated with each Drosophila Piwi protein and find that Piwi and Aubergine bind RNAs that are predominantly antisense to transposons, whereas Ago3 complexes contain predominantly sense piRNAs. As in mammals, the majority of Drosophila piRNAs are derived from discrete genomic loci. These loci comprise mainly defective transposon sequences, and some have previously been identified as master regulators of transposon activity. Our data suggest that heterochromatic piRNA loci interact with potentially active, euchromatic transposons to form an adaptive system for transposon control. Complementary relationships between sense and antisense piRNA populations suggest an amplification loop wherein each piRNA-directed cleavage event generates the 5’ end of a new piRNA. Thus, sense piRNAs, formed following cleavage of transposon mRNAs, may enhance production of antisense piRNAs, complementary to active elements, by directing cleavage of transcripts from master control loci. Keywords: small RNA libraries from Drosophila ovaries
Project description:The identification of RNAs that are recognized by RNA-binding proteins (RNA-BPs) using techniques such as Crosslinking and Immunoprecipitation (CLIP) has revolutionized the genome-wide discovery of RNA-BP RNA targets. Among the different versions of CLIP that have been developed, the use of photoactivable nucleoside analogs has resulted in high efficiency photoactivable ribonucleoside-enhanced CLIP (PAR-CLIP) in vivo. Nonetheless, PAR-CLIP has not yet been applied in prokaryotes. To determine if PAR-CLIP can be used in prokaryotes, we determined suitable conditions for the incorporation of 4-thiouridine (4SU), a photoactivable nucleoside, into E. coli RNA and for the isolation of RNA crosslinked to RNA-BPs of interest. Applying this technique to Hfq, a well-characterized regulator of small RNA (sRNA)-messenger RNA (mRNA) interactions, we showed that PAR-CLIP identified most of the known sRNA targets of Hfq, as well as functionally relevant sites of Hfq-mRNA interactions at nucleotide resolution. Based on our findings, PAR-CLIP represents an improved method to identify both the RNAs and the specific regulatory sites that are recognized by RNA-BPs in prokaryotes.
Project description:Piwi-interacting RNAs (piRNAs) suppress transposon activity in animal germ cells. In the Drosophila ovary, primary Aubergine (Aub)-bound antisense piRNAs initiate the ping-pong cycle to produce secondary AGO3-bound sense piRNAs. This increases the number of secondary Aub-bound antisense piRNAs that can act to destroy transposon mRNAs. Here we show that Krimper (Krimp), a Tudor-domain protein, directly interacts with piRNA-free AGO3 to promote symmetrical dimethylarginine (sDMA) modification, ensuring sense piRNA-loading onto sDMA-modified AGO3. In aub mutant ovaries, AGO3 associates with ping-pong signature piRNAs, suggesting AGO3’s compatibility with primary piRNA loading. Krimp sequesters ectopically expressed AGO3 within Krimp bodies in cultured ovarian somatic cells (OSCs), in which only the primary piRNA pathway operates. Upon krimp-RNAi in OSCs, AGO3 loads with piRNAs, further showing the capacity of AGO3 for primary piRNA loading. We propose that Krimp enforces an antisense bias on piRNA pools by binding AGO3 and blocking its access to primary piRNAs. In order to investigate function of Krimp in piRNA pathway, sequencing of Piwi subfamily protein associated small RNAs was performed using adult Drosophila ovaries and Ovarian Somatic Cells (OSCs) depleted for Krimp or Aub.