Mutations in the poly(A) ribonuclease (PARN) gene cause telomere diseases including familial idiopathic pulmonary fibrosis (IPF) and dyskeratosis congenita (DC)1,2, but how PARN deficiency impacts telomere maintenance is unclear. Here, using somatic cells and induced pluripotent stem (iPS) cells from DC patients with PARN mutations, we show that PARN is required for the 3' end maturation of the telomerase RNA component (TERC). Patient cells as well as immortalized cells in which PARN is disrupted show decreased levels of TERC. Deep sequencing of TERC RNA 3' termini reveals that PARN is required for removal of posttranscriptionally acquired oligo(A) tails that target nuclear RNAs for degradation. Diminished TERC levels and the increased oligo(A) forms of TERC are normalized by restoring PARN, which is limiting for TERC maturation in cells. Our results reveal a novel role for PARN in the biogenesis of TERC, and provide a mechanism linking PARN mutations to telomere diseases. Overall design: mRNA sequencing of fibroblasts, induced pluripotent stem cells, and 293 cell line.
Poly(A)-specific ribonuclease (PARN) mediates 3'-end maturation of the telomerase RNA component.
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View SamplesThe telomerase RNA component (TERC) is a critical determinant of cellular self renewal. Poly(A)-specific ribonuclease (PARN) is required for post-transcriptional maturation of TERC. PARN mutations lead to incomplete 3' end processing and increased destruction of nascent TERC RNA transcripts, resulting in telomerase deficiency and telomere diseases. Here, we determined that overexpression of TERC increased telomere length in PARN-deficient cells and hypothesized that decreasing post-transcriptional 3' oligo-adenylation of TERC would counteract the deleterious effects of PARN mutations. Inhibition of the noncanonical poly(A) polymerase PAP-associated domain–containing 5 (PAPD5) increased TERC levels in PARN-mutant patient cells. PAPD5 inhibition was also associated with increases in TERC stability, telomerase activity, and telomere elongation. Our results demonstrate that manipulating post-transcriptional regulatory pathways may be a potential strategy to reverse the molecular hallmarks of telomere disease. Overall design: mRNA sequencing of induced pluripotent stem cells and 293 cell line.
Posttranscriptional manipulation of TERC reverses molecular hallmarks of telomere disease.
Specimen part, Subject
View SamplesPolycomb Repressive Complex 2 (PRC2) catalyzes histone H3 lysine 27 tri-methylation, an epigenetic modification associated with gene repression. H3K27me3 is enriched at the promoters of a large cohort of developmental genes in embryonic stem cells (ESCs). Loss of H3K27me3 leads to a failure of ESCs to properly differentiate, which presents a major roadblock for dissecting the precise roles of PRC2 activity during lineage commitment. While recent studies suggest that loss of H3K27me3 leads to changes in DNA methylation in ESCs, how these two pathways coordinate to regulate gene expression programs during lineage commitment is poorly understood. Here, we analyzed gene expression and DNA methylation levels in several PRC2 mutant ESC lines that maintain varying levels of H3K27me3. We found that maintenance of intermediate levels of H3K27me3 allowed for proper temporal activation of lineage genes during directed differentiation of ESCs to spinal motor neurons (SMNs). However, genes that function to specify other lineages failed to be repressed, suggesting that PRC2 activity is necessary for lineage fidelity. We also found that H3K27me3 is antagonistic to DNA methylation in cis. Furthermore, loss of H3K27me3 leads to a gain in promoter DNA methylation in developmental genes in ESCs and in lineage genes during differentiation. Thus, our data suggest a role for PRC2 in coordinating dynamic gene repression while protecting against inappropriate promoter DNA methylation during differentiation. Overall design: Embryonic Stem Cell (ESC) lines mutant for PRC2 core components Suz12 (Suz12GT and Suz12delta) and Eed (Eednull) were subjected to in vitro directed differentiation down the spinal motor neuron lineage. ESCs and day 5 differentiated cells from the three mutant lines and wild-type were used for RNA-seq.
Polycomb Repressive Complex 2 regulates lineage fidelity during embryonic stem cell differentiation.
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View SamplesHost cells harbor various intrinsic mechanisms to restrict viral infections as a first line of antiviral defense. Viruses have evolved various countermeasures against these antiviral mechanisms. Here we show that N-Myc Downstream-Reguated Gene 1 (NDRG1) limits productive HCV infection by inhibiting viral assembly. Interestingly, HCV infection down-regulates NDRG1 protein and mRNA expression. Loss of NDRG1 increases the size and number of lipid droplets, which are the sites of HCV assembly. HCV suppresses NDRG1 expression by up-regulating MYC, which directly inhibits the transcription of NDRG1.
N-Myc Downstream-Regulated Gene 1 Restricts Hepatitis C Virus Propagation by Regulating Lipid Droplet Biogenesis and Viral Assembly.
Cell line, Treatment
View SamplesIdentification of genes regulated by GATA-1 independent of the cofactor FOG-1.
Friend of GATA-1-independent transcriptional repression: a novel mode of GATA-1 function.
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View SamplesPURPOSE
Gene expression profiling reveals novel biomarkers in nonsmall cell lung cancer.
Specimen part, Disease
View SamplesESCs and NPCs are two setm cell types which rely on expression of the transcription factor Sox2. We profilled gene expression in ESCs and NPCs to correlate genome-wide Sox2 ChIP-Seq data in these cells with expression of putative targets
SOX2 co-occupies distal enhancer elements with distinct POU factors in ESCs and NPCs to specify cell state.
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View SamplesStable activation of the WNT signaling effector beta-catenin (CTNNB1(ex3) in ovarian granulosa cells results in the formation of premalignant lesions that develop into granulosa cell tumors (GCTs) spontaneously later in life. Loss of the tumor suppressor gene Pten accelerates GCT formation in the CTNNB1 strain. Conversely, expression of oncogenic KRASG12D causes the dramatic arrest of proliferation, differentiation and apoptosis in granulosa cells, and consequently, small abnormal follicle-like structures devoid of oocytes accumulate in the ovary. Because of the potent anti-proliferative effects of KRASG12D in granulosa cells, we sought to determine if KRASG12D would block precancerous lesion and tumor formation in follicles of the CTNNB1 mutant mice. Unexpectedly, transgenic Ctnnb1;Kras mutant mice developed early-onset GCTs leading to premature death in a manner similar to theCtnnb1;Pten mutant mice. Moreover, the GCTs in the Ctnnb1;Kras mutant mice exhibited increased GC proliferation, decreased apoptosis and impaired differentiation. Microarray and RT-PCR analyses revealed that ovaries from mice expressing dominant-stable CTNNB1 with either Pten loss or KRAS activation were unpredictably similar. Specifically, gene regulatory processes induced by CTNNB1 were mostly enhanced by either KRAS activation or Pten loss in remarkably similar patterns and degree. Furthermore, the concomitant activation of CTNNB1 and KRAS in Sertoli cells resulted in the development of granulosa cell tumors of the testis. RT-PCR studies showed a partial overlap in gene regulatory processes associated with tumor development in the ovary and testis. Together, these results suggest that KRAS activation and Pten loss induce GCT development from premalignant lesions via highly similar molecular mechanisms.
Either Kras activation or Pten loss similarly enhance the dominant-stable CTNNB1-induced genetic program to promote granulosa cell tumor development in the ovary and testis.
Age, Specimen part
View SamplesWe used a combination of genome-wide and promoter-specific DNA binding and expression analyses to assess the functional roles of Myod and Myog in regulating the program of skeletal muscle gene expression. Our findings indicate that Myod and Myog have distinct regulatory roles at a similar set of target genes. At genes expressed throughout the program of myogenic differentiation, Myod can bind and recruit histone acetyltransferases. At early targets, Myod is sufficient for near full expression; whereas, at late expressed genes Myod initiates regional histone modification but is not sufficient for gene expression. At these late genes, Myog does not bind efficiently without Myod, however, transcriptional activation requires the combined activity of Myod and Myog. Therefore, the role of Myog in mediating terminal differentiation is, in part, to enhance expression of a subset of genes previously initiated by Myod.
Global and gene-specific analyses show distinct roles for Myod and Myog at a common set of promoters.
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View SamplesZebrafish (Danio rerio) were obtained from the Zebrafish Research Facility maintained in the Center for Environmental Biotechnology at the University of Tennessee. Fish husbandry, spawning, and experimental procedures were conducted with approval from the University of Tennessee Institutional Animal Care and Use Committee (Protocol #1690-1007). Water for holding fish and conducting experiments (hereafter referred to as fish water) consisted of MilliQ water (Millipore, Bedford, MA) with ions added: 19 mg/L NaHCO3, 1 mg/L sea salt (Instant Ocean Synthetic Sea Salt, Mentor, OH), 10 mg/L CaSO4, 10 mg/L MgSO4, 2 mg/L KCl. Embryos were obtained by spawning adult fish with no history of contaminant exposure. Fertilization of embryos took place at the same time ( 15 min.), such that larvae used in experiments were of similar age at the time of exposure. All activities (maintenance of adult fish, spawning, and experiments) were conducted in an environmental chamber with a temperature of 27 1 C and 14:10h light:dark photoperiod.
Global gene expression profiling in larval zebrafish exposed to microcystin-LR and microcystis reveals endocrine disrupting effects of Cyanobacteria.
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