Long noncoding RNAs transcribed by ERV-9 LTR retrotransposon act in cis to modulate long-range LTR enhancer function [ChIRP-Seq]
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ABSTRACT: LTR retrotransposons are repetitive DNA elements comprising ~10% of the human genome.However, Whether or how the LTR lncRNAs serve biological functions is largely unknown. Here we show that in primary human erythroblasts, lncRNAs transcribed from the LTR retrotransposons of ERV-9 human endogenous retrovirus regulated transcription of key erythroid genes. Genome wide ChIRP-Seq was carried out to detect the association of ERV-9 lncRNAs with the genomic DNA in the Day 13 erythroid cells from in vitro culture and phenylhydrazine treated Day 5 spleen cells from transgenic mice in vivo.
Project description:LTR retrotransposons are repetitive DNA elements comprising ~10% of the human genome. However, Whether or how the LTR lncRNAs serve biological functions is largely unknown. Here we show that in primary human erythroblasts, lncRNAs transcribed from the LTR retrotransposons of ERV-9 human endogenous retrovirus regulated transcription of key erythroid genes. Global knock-down of ERV-LTR lncRNAs was performed in the in vitro erythropoiesis system of human CD34 cells, and genome wide RNA-seq was carried out to detect the effect on transcription.
Project description:Transposon reactivation is an inherent danger in cells that lose epigenetic silencing during developmental reprogramming. In the mouse, LTR-retrotransposons, or endogenous retroviruses (ERV), account for most novel insertions and are expressed in the absence of histone H3 Lysine 9 trimethylation in preimplantation stem cells. We found abundant, 18 nt tRNA-derived small RNA (tRF) in these cells, and ubiquitously expressed 22 nt tRFs, that include the 3' terminal CCA of mature tRNAs, and target the tRNA primer binding site (PBS) essential for ERV reverse transcription. We show that the two most active ERV families, IAP and MusD/ETn, are major targets and are strongly inhibited by tRFs in retrotransposition assays. 22 nt tRFs post-transcriptionally silence coding-competent ERVs, while 18 nt tRFs specifically interfere with reverse transcription and retrotransposon mobility. The PBS offers a unique target to specifically inhibit LTR-retrotransposons and tRF-targeting is a potentially highly conserved mechanism of small RNA-mediated transposon control.
Project description:LTR retrotransposons are repetitive DNA elements comprising ∼10% of the human genome. However, LTR sequences are disproportionately present in human long, non-coding RNAs (lncRNAs). Whether and how the LTR lncRNAs serve biological functions are largely unknown. Here we show that in primary human erythroblasts, lncRNAs transcribed from the LTR retrotransposons of ERV-9 human endogenous retrovirus activated transcription of key erythroid genes and modulated ex vivo erythropoiesis. To dissect the functional mechanism of ERV-9 lncRNAs, we performed genome-wide RNA and ChIRP analyses before and after global knockdown or locus-specific deletion of ERV-9 lncRNAs in human erythroblasts carrying ∼4000 copies of the ERV-9 LTRs and in transgenic mouse erythroblasts carrying a single copy of the primate-specific ERV-9 LTR in the 100 kb human β-globin gene locus. We found that ERV-9 lncRNAs acted in cis to stabilize assembly of the ERV-9 LTR enhancer complex and facilitate long-range LTR enhancer function in activating transcription of downstream, cis-linked globin genes. Our findings suggested that LTR lncRNAs transcribed from many of the 4000 copies of ERV-9 LTR retrotransposons acted by a similar cis mechanism to modulate LTR enhancer function in activating transcription of downstream genes critical to cellular processes including erythropoiesis.
Project description:Recently developed methods applied to plant material, for example tissue culture during plant transformation, can induce genome instability by activating uncontrolled mobilization of LTR retrotransposons (LTR-TEs), the most abundant class of mobile genetic elements in plant genomes. Here we tested the use of Reverse Transcriptase inhibitors to avoid LTR-TE mobilization in plants. We demonstrated that the application of the drug Tenofovir in systems with high LTR-TE activity, like Arabidopsis and rice, allows generation of plants free from LTR-TE insertions without interfering with their development. We propose the use of Tenofovir as a new tool to both study LTR-TE transposition and to regenerate more genetically stable plant lines from tissue culture.
Project description:Recently developed methods applied to plant material, for example tissue culture during plant transformation, can induce genome instability by activating uncontrolled mobilization of LTR retrotransposons (LTR-TEs), the most abundant class of mobile genetic elements in plant genomes. Here we tested the use of Reverse Transcriptase inhibitors to avoid LTR-TE mobilization in plants. We demonstrated that the application of the drug Tenofovir in systems with high LTR-TE activity, like Arabidopsis and rice, allows generation of plants free from LTR-TE insertions without interfering with their development. We propose the use of Tenofovir as a new tool to both study LTR-TE transposition and to regenerate more genetically stable plant lines from tissue culture.
Project description:Sugarcane is an important crop worldwide for sugar production and increasingly, as a renewable energy source. Modern cultivars have polyploid, large complex genomes, with highly unequal contributions from ancestral genomes. Long Terminal Repeat retrotransposons (LTR-RTs) are the single largest components of most plant genomes and can substantially impact the genome in many ways. It is therefore crucial to understand their contribution to the genome and transcriptome, however a detailed study of LTR-RTs in sugarcane has not been previously carried out. Sixty complete LTR-RT elements were classified into 35 families within four Copia and three Gypsy lineages. Structurally, within lineages elements were similar, between lineages there were large size differences. Four distinct patterns were observed in sRNA mapping, the most unusual of which was that of Ale1, with very large numbers of 24nt sRNAs in the coding region. The results presented support the conclusion that distinct small RNA-regulated pathways in sugarcane target the lineages of LTR-RT elements. Individual LTR-RT sugarcane families have distinct structures, and transcriptional and regulatory signatures. Our results indicate that in sugarcane individual LTR-RT families have distinct behaviors and can potentially impact the genome in diverse ways. For instance, these transposable elements may affect nearby genes by generating a diverse set of small RNA's that trigger gene silencing mechanisms. There is also some evidence that ancestral genomes contribute significantly different element numbers from particular LTR-RT lineages to the modern sugarcane cultivar genome. Examination of small RNA populations in the sugarcane leaves that show matches against sugarcane LTR-RTs.
Project description:Sugarcane is an important crop worldwide for sugar production and increasingly, as a renewable energy source. Modern cultivars have polyploid, large complex genomes, with highly unequal contributions from ancestral genomes. Long Terminal Repeat retrotransposons (LTR-RTs) are the single largest components of most plant genomes and can substantially impact the genome in many ways. It is therefore crucial to understand their contribution to the genome and transcriptome, however a detailed study of LTR-RTs in sugarcane has not been previously carried out. Sixty complete LTR-RT elements were classified into 35 families within four Copia and three Gypsy lineages. Structurally, within lineages elements were similar, between lineages there were large size differences. Four distinct patterns were observed in sRNA mapping, the most unusual of which was that of Ale1, with very large numbers of 24nt sRNAs in the coding region. The results presented support the conclusion that distinct small RNA-regulated pathways in sugarcane target the lineages of LTR-RT elements. Individual LTR-RT sugarcane families have distinct structures, and transcriptional and regulatory signatures. Our results indicate that in sugarcane individual LTR-RT families have distinct behaviors and can potentially impact the genome in diverse ways. For instance, these transposable elements may affect nearby genes by generating a diverse set of small RNA's that trigger gene silencing mechanisms. There is also some evidence that ancestral genomes contribute significantly different element numbers from particular LTR-RT lineages to the modern sugarcane cultivar genome.
Project description:STN7-dependent phosphorylation of an as yet unknown thylakoid protein triggers the signaling events associated with the long-term acclimatory response (LTR). The LTR-associated signaling events regulate the expression of photosynthesis-related genes on the post-transcriptional level (nucleus), as indicated by transcript profiling in LTR mutants.