Tristetraprolin is a vertebrate CCCH tandem zinc finger protein that can bind to and destabilize certain mRNAs containing AU-rich element binding sites. zfs1 is the single gene in the fission yeast, Schizosaccharomyces pombe, that encodes a protein containing the critical features of the tristetraprolin zinc finger domain. zfs1 has been linked to pheromone signal transduction control and to the coordination of mitosis, but no biological function has been ascribed to the zfs1 protein. Through a functional genomics approach we compared transcript levels in wild-type and zfs1-deficient S. pombe strains; those elevated in the zfs1-deficient strain were examined for the presence of potential tristetraprolin-like binding sites. One such potential target transcript was encoded by arz1, a gene encoding a protein of unknown function that contains armadillo repeats. arz1 mRNA decay was inhibited in the zfs1-deficient strain when it was expressed under the control of a thiamine-repressible promoter. Mutations within one AU-rich element present in the arz1 3-untranslated region protected this transcript from zfs1-promoted decay, whereas mutating another potential binding site had no effect. Binding assays confirmed a direct interaction between zfs1 and arz1 mRNA-based probes; this interaction was eliminated when key residues were mutated in either zfs1 zinc finger. zfs1 and its targets in S. pombe represent a useful model system for studies of zinc finger protein/AU-rich element interactions that result in mRNA decay.
Characterization of zfs1 as an mRNA-binding and -destabilizing protein in Schizosaccharomyces pombe.
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View SamplesTristetraprolin (TTP) is a tandem CCCH zinc finger protein that was identified through its rapid induction by mitogens in fibroblasts. Studies of TTP-deficient mice, and cells derived from them, showed that TTP could bind to certain AU-rich elements in mRNAs, leading to increases in the rates of mRNA deadenylation and destruction. Known physiological target
Novel mRNA targets for tristetraprolin (TTP) identified by global analysis of stabilized transcripts in TTP-deficient fibroblasts.
Cell line
View SamplesArsenic is a potent environmental toxin and a cause of numerous health problems. Most studies have assumed that arsenic-induced changes in mRNA levels result from effects on gene transcription. The influence of arsenic on post-transcriptional regulation, another important locus of gene expression control, has remained largely unexplored.
Global analysis of posttranscriptional gene expression in response to sodium arsenite.
Cell line
View SamplesMembers of the tristetraprolin (TTP) family of CCCH tandem zinc finger proteins can bind directly to AU-rich elements in mRNAs and promote transcript deadenylation and decay. The yeast Schizosaccharomyces pombe expresses a single TTP family member, Zfs1p, that has been linked to the mating response pathway and septum formation. We showed previously that Zfs1p can bind to and promote the destabilization of AU-rich element-containing transcripts. In this study, we identified additional target transcripts by comparing transcript levels in wild type and zfs1 mutant yeast, using deep sequencing and microarray approaches. We also used direct RNA sequencing to determine the locations of the polyA tails in both wild type and mutant strains, and to confirm the presence of potential Zfs1p target sequences within the mRNA. These studies identified a set of transcripts containing potential Zfs1p binding sites that accumulated significantly in the zfs1 mutants; a subset of these turned over more slowly in the zfs1 mutant strain, and bound directly to Zfs1p in co-immunoprecipitations. One apparent direct target encodes the transcription factor Cbf12p, which is known to increase cell-cell adhesion and flocculation when over-expressed. Studies of zfs1 and cbf12 double mutants demonstrated that the increased flocculation seen in zfs1 mutants is due, at least in part, to a direct effect on the turnover of cbf12 mRNA, leading in turn to changes in the levels of its transcriptionally regulated genes. These data suggest that Zfs1p can both directly and indirectly regulate the levels of transcripts involved in cell-cell adhesion in this species.
Posttranscriptional regulation of cell-cell interaction protein-encoding transcripts by Zfs1p in Schizosaccharomyces pombe.
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View SamplesThe ZFP36L3 protein is a rodent-specific, placenta- and yolk sac-specific member of the tristetraprolin (TTP) family of CCCH tandem zinc finger proteins. These proteins bind to AU-rich elements in target mRNAs, and promote their deadenylation and decay. Mice deficient in ZFP36L3 exhibited decreased neonatal survival rates, but no apparent morphological changes in the placenta or surviving offspring. Zfp36l3 is paternally imprinted, with profound parent-of-origin effects on gene expression. RNASeq of KO placental mRNA revealed many significantly affected transcripts, some of which exhibited decreased decay rates in differentiated trophoblast stem cells derived from KO blastocysts. The type 1 transferrin receptor mRNA was unexpectedly decreased in KO placentas, despite an increase in its stability. This receptor is critical for placental iron uptake from the maternal circulation, and its decrease was accompanied by decreased iron stores in the KO fetus, suggesting that this intrauterine deficiency might have deleterious consequences in later life. Overall design: Examination of gene expression differences in yolk sac tissue between wild-type and knockout mice groups with 4 biological replicates in each group
Deficiency of the placenta- and yolk sac-specific tristetraprolin family member ZFP36L3 identifies likely mRNA targets and an unexpected link to placental iron metabolism.
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Global target mRNA specification and regulation by the RNA-binding protein ZFP36.
Cell line, Treatment
View SamplesTristetraprolin/ZFP36/TTP and ELAVL1/HuR are two disease-relevant RNA-binding proteins (RBPs) that both interact with AU-rich sequences but have antagonistic roles. While ELAVL1 binding has been profiled in several studies, the precise in vivo binding specificity of ZFP36 has not been investigated on a global scale. We determined ZFP36 binding preferences using cross-linking and immunoprecipitation in human embyonic kidney cells and examined combinatorial regulation of AU-rich elements by ZFP36 and ELAVL1. Among the targets ZFP36 binds and negatively regulates the mRNA of genes encoding proteins necessary for immune function and cancer, and other RBPs. Using partial correlation analysis, we were able to quantify the association between ZFP36 binding sites and differential target RNA abundance from ZFP36 overexpression independent of effects from confounding features, such as 3 UTR length. We identified thousands of overlapping ZFP36 and ELAVL1 binding sites, in 1,313 genes. ZFP36 preferentially interacts with and regulates AU-rich sequences while ELAVL1 prefers predominantly U- and CU-rich sequences. RNA target specificity identified by global in vivo ZFP36-mRNA interactions were quantitatively similar to previously reported in vitro binding affinities. ZFP36 and ELAVL1 both bind an overlapping spectrum of RNA sequences, yet with differential relative preferences that dictate combinatorial regulatory potential. Our findings and methodology delineate an approach to untangle the in vivo combinatorial regulation by RNA-binding proteins.
Global target mRNA specification and regulation by the RNA-binding protein ZFP36.
Cell line, Treatment
View SamplesRNA-binding proteins (RBPs) facilitate post-transcriptional control of eukaryotic gene expression at multiple levels. The RBP tristetraprolin (TTP/Zfp36) is a signal-induced phosphorylated anti-inflammatory protein guiding unstable mRNAs of pro-inflammatory proteins for degradation and preventing translation. Using iCLIP, we have identified numerous mRNA targets bound by wild-type TTP and by a non-MK2-phosphorylatable TTP mutant (TTP-AA) in 1h LPS-stimulated macrophages and correlated their interaction with TTP to changes at the level of mRNA abundance and translation in a transcriptome-wide manner. The close similarity of the transcriptome of TTP-deficient and TTP-expressing macrophages upon short LPS stimulation suggested an effective inactivation of TTP by MK2 under these conditions whereas retained RNA-binding capacity of TTP-AA to 3’UTRs caused profound changes in the transcriptome and translatome, altered NF-?B-activation and induced cell death. Increased TTP binding to the 3''UTR of feedback inhibitor mRNAs, such as Ier3, Dusp1 or Tnfaip3, in the absence of MK2-dependent TTP neutralization resulted in a strong reduction of their protein synthesis contributing to the deregulation of the NF-?B-signaling pathway. Taken together, our study uncovers a role for TTP in NF-?B-signaling and highlights the importance of fine-tuned TTP activity-regulation by MK2 in order to control feedback signaling during the inflammatory response. Overall design: Comparison of the transcriptomes of TTP knockout macrophages inducibly expressing GFP, GFP-TTP or GFP-TTP-AA (S52A, S178A) phosphorylation mutant during 1h LPS stimulation. 3 biological replicates per genotype and condition.
The RNA-binding protein TTP is a global post-transcriptional regulator of feedback control in inflammation.
Specimen part, Subject
View SamplesA recent two-year NTP cancer bioassay showed a marked increase in the incidence of malignant mesothelioma arising from the tunica vaginalis in male Fischer 344/N rats exposed to Vinylidene chloride (VDC). Aged male F344/N rats are prone to developing spontaneous peritoneal mesotheliomas, which also arise predominantly from the tunica vaginalis of the testes. A definitive mechanism for the observed increased incidence in VDC-exposed rats is unknown. Investigation of the molecular alterations that occur in mesotheliomas from vehicle control and VDC-exposed rats may provide insight into their pathogenesis, as well enable a better understanding regarding the mechanisms underlying chemically induced mesothelioma in rodents. Mesothelial cell function represents a complex interplay of pathways related to host defense mechanisms and maintenance of cellular homeostasis. Global gene expression profiles of spontaneous mesotheliomas from vehicle control male F344/N rats from various two-year National Toxicology Program carcinogenicity bioassays were compared to mesotheliomas from VDC-exposed rats to characterize the molecular features that are present in mesotheliomas from VDC-exposed animals, and to elucidate tumor-specific gene expression profiles. The resulting gene expression pattern showed that mesotheliomas from VDC-exposed animals are genomically very different from spontaneous tumors; while both tumor types are characterized by alterations in gene expression associated with carcinogenic pathways (oncogenes, tumor suppressor genes, growth factors, etc.), mesotheliomas from VDC-exposed animals are associated with increased dysreguation of immune pathways and inflammatory mediators. Alterations in these pathways may suggest a pro-inflammatory and immune dysfunction signature as one mechanism in the observed increased incidence of these tumors in VDC-exposed animals.
Spontaneous mesotheliomas in F344/N rats are characterized by dysregulation of cellular growth and immune function pathways.
Disease
View SamplesThis SuperSeries is composed of the SubSeries listed below.
Tristetraprolin impairs myc-induced lymphoma and abolishes the malignant state.
Specimen part
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