Contrasting effects of whole-body and hepatocyte-specific deletion of the RNA polymerase III repressor Maf1 in the mouse [RNA-Seq]
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ABSTRACT: MAF1 is a nutrient-sensitive, TORC1-regulated repressor of RNA polymerase III (Pol III). MAF1 downregulation leads to increased lipogenesis in Drosophila melanogaster, Caenorhabditis elegans, and mice. However, Maf1−/− mice are lean as increased lipogenesis is counterbalanced by futile pre-tRNA synthesis and degradation, resulting in increased energy expenditure. We compared Chow-fed Maf1−/− mice with Chow- or High Fat (HF)-fed Maf1hep−/− mice that lack MAF1 specifically in hepatocytes. Unlike Maf1−/− mice, Maf1hep−/− mice become heavier and fattier than control mice with old age and much earlier under a HF diet. Liver ChIPseq, RNAseq and proteomics analyses indicate increased Pol III occupancy at Pol III genes, very few differences in mRNA accumulation, and protein accumulation changes consistent with increased lipogenesis. Futile pretRNA synthesis and degradation in the liver, as likely occurs in Maf1hep−/− mice, thus seems insufficient to counteract increased lipogenesis. Indeed, RNAseq and metabolite profiling indicate that liver phenotypes of Maf1−/− mice are strongly influenced by systemic inter-organ communication. Among common changes in the three phenotypically distinct cohorts, Angiogenin downregulation is likely linked to increased Pol III occupancy of tRNA genes in the Angiogenin promoter.
Project description:MAF1 is a nutrient-sensitive, TORC1-regulated repressor of RNA polymerase III (Pol III). MAF1 downregulation leads to increased lipogenesis in Drosophila melanogaster, Caenorhabditis elegans, and mice. However, Maf1−/− mice are lean as increased lipogenesis is counterbalanced by futile pre-tRNA synthesis and degradation, resulting in increased energy expenditure. We compared Chow-fed Maf1−/− mice with Chow- or High Fat (HF)-fed Maf1hep−/− mice that lack MAF1 specifically in hepatocytes. Unlike Maf1−/− mice, Maf1hep−/− mice become heavier and fattier than control mice with old age and much earlier under a HF diet. Liver ChIPseq, RNAseq and proteomics analyses indicate increased Pol III occupancy at Pol III genes, very few differences in mRNA accumulation, and protein accumulation changes consistent with increased lipogenesis. Futile pretRNA synthesis and degradation in the liver, as likely occurs in Maf1hep−/− mice, thus seems insufficient to counteract increased lipogenesis. Indeed, RNAseq and metabolite profiling indicate that liver phenotypes of Maf1−/− mice are strongly influenced by systemic inter-organ communication. Among common changes in the three phenotypically distinct cohorts, Angiogenin downregulation is likely linked to increased Pol III occupancy of tRNA genes in the Angiogenin promoter.
Project description:The conserved phosphoprotein MAF1 is the main known direct repressor of RNA polymerase III (Pol III). MAF1 is phosphorylated and inactivated by the nutrient-sensing TORC1 kinase, making MAF1 a nutrient effector for Pol III transcription. MAF1 has been associated with lipid metabolism in D. melanogaster, C. elegans, and the mouse. However, whereas downregulation of Maf1 generally increases lipogenesis, Maf1-/- mice are lean even under a High Fat (HF) diet. Here we compared Maf1-/- mice fed a Chow diet with mice lacking Maf1 specifically in hepatocytes (Maf1hep-/- mice) fed either a Chow or HF diet. Unlike Maf1-/- mice, Maf1hep-/- mice become slightly heavier than control mice at an old age and much earlier under a HF diet, with increased adiposity. Liver ChIPseq, RNAseq and proteomics analyses indicate increased Pol III occupancy at Pol III genes, very few differences in mRNA accumulation, and subtle changes in protein accumulation that are consistent with increased lipogenesis. RNAseq and metabolite profiling indicate that liver phenotypes of Maf1-/- mice are strongly influenced by systemic inter-organ communication. Notable changes observed in the three phenotypically distinct cohorts include downregulation of Mouse Urinary Proteins, upregulation of Cyp2a4 expression, suggestive of an alteration of Growth Hormone levels or secretion pattern, and downregulation of Angiogenin, a phenomenon that might be directly linked to increased Pol III occupancy of tRNA genes in the main Angiogenin promoter region.
Project description:RNA polymerase III (pol III) synthesizes short non-coding RNAs, many of which, including tRNAs, Rpph1 RNA, Rn5s rRNA, and Rmrp RNA, are essential for translation. Accordingly, pol III activity is tightly regulated with cell growth and proliferation by factors such as MYC, RB1, TRP53, and MAF1. MAF1 is a repressor of pol III transcription whose activity is controlled by phosphorylation; in particular, it is inactivated through phosphorylation by mTORC1 kinase, a sensor of nutrient availability. Pol III regulation is thus sensitive to environmental cues, yet a diurnal profile of pol III transcription activity is so far lacking. Here we document pol III occupancy of its target genes in mouse liver during the diurnal cycle and show that pol III occupancy rises before the onset of the night, stays high during the night, when mice normally ingest food and when translation is increased, and decreases in daytime. By comparing diurnal pol III occupancy in wild-type mice, arrhythmic mice owing to inactivation of the Arntl gene, mice fed at regular intervals during both night and day, and mice lacking the Maf1 gene, we show that whereas higher pol III occupancy during the night reflects a MAF1-dependent response to feeding, the rise of pol III occupancy before the onset of the night reflects a circadian clock-dependent response. Thus, pol III transcription during the diurnal cycle is regulated both in response to nutrients and by the circadian clock, which allows anticipatory pol III transcription.
Project description:RNA polymerase III (pol III) synthesizes short non-coding RNAs, many of which, including tRNAs, Rpph1 RNA, Rn5s rRNA, and Rmrp RNA, are essential for translation. Accordingly, pol III activity is tightly regulated with cell growth and proliferation by factors such as MYC, RB1, TRP53, and MAF1. MAF1 is a repressor of pol III transcription whose activity is controlled by phosphorylation; in particular, it is inactivated through phosphorylation by mTORC1 kinase, a sensor of nutrient availability. Pol III regulation is thus sensitive to environmental cues, yet a diurnal profile of pol III transcription activity is so far lacking. Here we document pol III occupancy of its target genes in mouse liver during the diurnal cycle and show that pol III occupancy rises before the onset of the night, stays high during the night, when mice normally ingest food and when translation is increased, and decreases in daytime. By comparing diurnal pol III occupancy in wild-type mice, arrhythmic mice owing to inactivation of the Arntl gene, mice fed at regular intervals during both night and day, and mice lacking the Maf1 gene, we show that whereas higher pol III occupancy during the night reflects a MAF1-dependent response to feeding, the rise of pol III occupancy before the onset of the night reflects a circadian clock-dependent response. Thus, pol III transcription during the diurnal cycle is regulated both in response to nutrients and by the circadian clock, which allows anticipatory pol III transcription.
Project description:MAF1 represses Pol III-mediated transcription by interfering with TFIIIB and Pol III. Herein, we found that MAF1 knockdown induced CDKN1A transcription and chromatin looping concurrently with Pol III recruitment. Simultaneous knockdown of MAF1 with Pol III or BRF1 (subunit of TFIIIB) diminished the activation and looping effect, which indicates that recruiting Pol III was required for activation of Pol II-mediated transcription and chromatin looping. ChIP analysis after MAF1 knockdown indicated enhanced binding of Pol III and BRF1, as well as of CFP1, p300, and PCAF, which are factors that mediate active histone marks, along with the binding of TBP and POLR2E to the CDKN1A promoter. Simultaneous knockdown with Pol III abolished these regulatory events. Similar results were obtained for GDF15. Our results reveal a novel mechanism by which MAF1 and Pol III regulate the activity of a protein-coding gene transcribed by Pol II.
Project description:MAF1 represses Pol III-mediated transcription by interfering with TFIIIB and Pol III. Herein, we found that MAF1 knockdown induced CDKN1A transcription and chromatin looping concurrently with Pol III recruitment. Simultaneous knockdown of MAF1 with Pol III or BRF1 (subunit of TFIIIB) diminished the activation and looping effect, which indicates that recruiting Pol III was required for activation of Pol II-mediated transcription and chromatin looping. ChIP analysis after MAF1 knockdown indicated enhanced binding of Pol III and BRF1, as well as of CFP1, p300, and PCAF, which are factors that mediate active histone marks, along with the binding of TBP and POLR2E to the CDKN1A promoter. Simultaneous knockdown with Pol III abolished these regulatory events. Similar results were obtained for GDF15. Our results reveal a novel mechanism by which MAF1 and Pol III regulate the activity of a protein-coding gene transcribed by Pol II. Knockdown assay was performed using siRNA obtained from MISSION®RNA (Sigma). Inhibition of expression of Pol III (SASI_Hs01_00046568) and MAF1 (SASI_Hs01_00135954) was achieved by transfection with LipofectamineTM RNAiMax (Invitrogen) according to the manufacturer’s protocol. MISSION® siRNA Universal Negative Control (Sigma) was used as knockdown control. Cells were transfected in serum-free medium. After 8 h, the siRNA containing medium was replaced with complete medium.
Project description:RNA polymerase (pol) III transcribes a variety of small untranslated RNAs that are involved in essential cellular processes that include transcription, RNA processing, and translation. RNA pol III and its components are altered in various human developmental disorders, yet their roles in cell fate determination and development are poorly understood. Here we demonstrate that Maf1, a transcriptional repressor, promotes induction of mouse embryonic stem cells into mesoderm and their terminal differentiation into adipocytes. Reduced Maf1 expression in preadipocytes impairs adipogenesis while ectopic Maf1 expression in Maf1-/- deficient cells enhances differentiation. RNA pol III repression by either chemical inhibition or knockdown of Brf1, promotes adipogenesis. Altered RNA pol III-dependent transcription produces select changes in RNA pol II-derived transcripts with a significant enrichment of adipogenic gene signatures. Furthermore, RNA pol III-mediated transcription positively regulates long non-coding RNA H19 and Wnt6 expression, established adipogenesis inhibitors. Together, these studies reveal an important and unexpected function for RNA pol III-mediated transcription and Maf1 in mesoderm induction and cellular differentiation.
Project description:Maf1, a key repressor of RNA polymerase III-mediated transcription, has been shown to promote mesoderm formation in vitro. Here, we show, for the first time, that Maf1 plays a critical role in the regulation of osteoblast differentiation. We also found that, in contrast to MAF1 overexpression, other perturbations that repress RNA pol III transcription, including Brf1 knockdown and the chemical inhibition of RNA pol III by ML-60218, inhibited osteoblast differentiation. RNA-seq was used to determine the basis for these opposing actions on osteoblast differentiation. RNA polymerase III-dependent transcription was manipulated in ST2 stromal cells by Brf1 or Maf1 knockdown, ML-60218 treatment and MAF1 overexpression. The ST2 cells were then tested for their capacity to differentiate into osteoblasts. RNA-seq was performed on day 0, before differentiation and day 4 after differentiation medium was added. The modalities used to perturb RNA pol III transcription resulted in distinct changes gene expression, indicating that this transcription process is highly sensitive and triggers diverse gene expression programs and phenotypic outcomes. Specifically, Maf1 induced genes in ST2 cells known to promote osteoblast differentiation. Furthermore, genes that are induced during osteoblast differentiation displayed codon bias.
Project description:In higher eukaryotes, an important mechanism to tune translation in different tissues and conditions is mTORC1-dependent regulation of tRNAs transcription by RNA polymerase III (Pol III), as the relative amount of tRNAs tightly coordinates with the translational needs of the cell. mTORC1 contributes to regulate protein synthesis through its direct substrate MAF1, which functions as a negative regulator of Pol III transcription in response to stimuli such as serum starvation or rapamycin treatment. Here, we applied ChIP-seq to examine the Pol III occupancy profile in human fibroblasts and report evidence of a genome wide, MAF1-dependent coordinated response to favorable or stress growth conditions. Strikingly, while a set of genes is extremely responsive in terms of Pol III binding, other genes are mostly unperturbed, yet associated with transcriptionally engaged polymerases as revealed by nascent EU-labeled RNA-seq (neuRNA-seq). As shown by DamIP-seq, the responsiveness of a subset of genes is tightly connected to the rapid and transient interaction of MAF1 with DNA-bound Pol III. We performed duplicate ChIP-seq experiments for the Rpc4 (POLR3D) subunit of RNA polymerase III in IMR90hTert cells grown in the presence of fetal bovine serum (FBS), serum starved (SS), serum starved and treated with insulin (SS+I), serum starved and treated with insulin and rapamycin (SS+R+I). Additional ChIP-seq profiles were generated in cells treated with MAF1 siRNAs and serum starved. MAF1 binding was addressed by DamIP-seq, using two replicates per clone of IMR90hTert cells expressing HA-tagged MAF1-DamK9A (2 different clones) or EGFP-DamK9A (2 different clones). To monitor dynamic transcription profiles we did neusRNA-seq in IMR90hTert cells EU-labeled or mock (DMSO)-labeled. For both DamIP-seq and neusRNA-seq, cells were either unperturbed or serum starved.
Project description:In higher eukaryotes, an important mechanism to tune translation in different tissues and conditions is mTORC1-dependent regulation of tRNAs transcription by RNA polymerase III (Pol III), as the relative amount of tRNAs tightly coordinates with the translational needs of the cell. mTORC1 contributes to regulate protein synthesis through its direct substrate MAF1, which functions as a negative regulator of Pol III transcription in response to stimuli such as serum starvation or rapamycin treatment. Here, we applied ChIP-seq to examine the Pol III occupancy profile in human fibroblasts and report evidence of a genome wide, MAF1-dependent coordinated response to favorable or stress growth conditions. Strikingly, while a set of genes is extremely responsive in terms of Pol III binding, other genes are mostly unperturbed, yet associated with transcriptionally engaged polymerases as revealed by nascent EU-labeled RNA-seq (neuRNA-seq). As shown by DamIP-seq, the responsiveness of a subset of genes is tightly connected to the rapid and transient interaction of MAF1 with DNA-bound Pol III. We performed duplicate ChIP-seq experiments for the Rpc4 (POLR3D) subunit of RNA polymerase III in IMR90hTert cells grown in the presence of fetal bovine serum (FBS), serum starved (SS), serum starved and treated with insulin (SS+I), serum starved and treated with insulin and rapamycin (SS+R+I). Additional ChIP-seq profiles were generated in cells treated with MAF1 siRNAs and serum starved. MAF1 binding was addressed by DamIP-seq, using two replicates per clone of IMR90hTert cells expressing HA-tagged MAF1-DamK9A (2 different clones) or EGFP-DamK9A (2 different clones). To monitor dynamic transcription profiles we did neusRNA-seq in IMR90hTert cells EU-labeled or mock (DMSO)-labeled. For both DamIP-seq and neusRNA-seq, cells were either unperturbed or serum starved.