Dynamics of RNA localization to nuclear speckles are connected to splicing efficiency [ARTR-seq]
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ABSTRACT:
ORGANISM(S): Homo sapiens
PROVIDER: GSE255206 | GEO | 2024/09/05
REPOSITORIES: GEO
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Project description:Nuclear speckles, a type of membraneless nuclear organelle in higher eukaryotic cells, play a vital role in gene expression regulation. Using the reverse transcription-based RBP binding sites sequencing (ARTR-seq) method, we study human transcripts associated with nuclear speckles. We identify three gene groups whose transcripts demonstrate different speckle localization properties and dynamics – stably enriched in nuclear speckle post-transcriptionally, transiently enriched in speckles at the pre-mRNA stage co-transcriptionally, and not enriched in speckles. We show that nuclear speckles specifically facilitate splicing of speckle-enriched transcripts. We further reveal RNA sequence features contributing to transcript speckle localization, underscoring a tight interplay between genome organization, RNA cis-elements, and transcript speckle enrichment, and connecting transcript speckle localization with splicing logic. Finally, we show that speckles can act as hubs for the regulated retention of introns during cellular stress. Collectively, our data highlight a role of nuclear speckles in both co- and post-transcriptional splicing regulation.
2024-09-05 | GSE255207 | GEO
Project description:Nuclear speckles are membraneless organelles that associate with active transcription sites and participate in post-transcriptional mRNA processing. During the cell cycle, nuclear speckles dissolve following phosphorylation of their protein components. Here, we identify the PP1 family as the phosphatases that counteract kinase-mediated dissolution. PP1 overexpression increases speckle cohesion and leads to retention of polyadenylated RNA within speckles and the nucleus. Using APEX2 proximity labeling combined with RNA-sequencing, we characterized the relationship between the cohesion of nuclear speckles and the recruitment of specific RNAs. We find that many transcripts are preferentially enriched within nuclear speckles compared to the nucleoplasm, particularly chromatin- and nucleus-associated transcripts. While total polyadenylated RNA retention increased with nuclear speckle cohesion, the ratios of most mRNA species to each other were constant, indicating non-selective, or proportional, retention. We then explored whether nuclear speckle cohesion changes in response to environmental perturbations associated with changes in kinase or phosphatase activity. We found that cellular responses to heat shock, oxidative stress, and hypoxia include changes to the cohesion of nuclear speckles and mRNA retention. Our results demonstrate that tuning the material properties of nuclear speckles provides a mechanism for the acute control of mRNA localization.
2024-11-28 | PXD055775 | Pride
Project description:Nuclear speckles are membraneless organelles that associate with active transcription sites and participate in post-transcriptional mRNA processing. During mitosis, nuclear speckles dissolve following phosphorylation of their protein components. Here, we identify PP1 phosphatases as responsible for counteracting kinase-mediated dissolution. Their overexpression increases speckle cohesion and leads to retention of polyadenylated RNA within speckles and the nucleus. By performing APEX2 proximity labeling combined with RNA-sequencing, we characterized the association of specific RNAs with nuclear speckles depending on their cohesion state. We find that many transcripts are preferentially enriched within nuclear speckles compared to the nucleoplasm, particularly chromatin- and nucleus-associated transcripts. While total polyadenylated RNA retention increased with greater nuclear speckle cohesion, the ratios of most mRNA species to each other were constant, indicating non-selective, or proportional, retention. We then explored whether nuclear speckle cohesion changes in response to environmental perturbations associated with changes in kinase or phosphatase activity. We found that cellular responses to heat shock, oxidative stress, and hypoxia include changes to the cohesion of nuclear speckles and mRNA retention. Our results demonstrate that tuning the material properties of nuclear speckles provides a mechanism for the acute control of mRNA localization.
2024-11-10 | GSE240891 | GEO
Project description:Nuclear speckles are membraneless organelles that associate with active transcription sites and participate in post-transcriptional mRNA processing. During mitosis, nuclear speckles dissolve following phosphorylation of their protein components. Here, we identify PP1 phosphatases as responsible for counteracting kinase-mediated dissolution. Their overexpression increases speckle cohesion and leads to retention of polyadenylated RNA within speckles and the nucleus. By performing APEX2 proximity labeling combined with RNA-sequencing, we characterized the association of specific RNAs with nuclear speckles depending on their cohesion state. We find that many transcripts are preferentially enriched within nuclear speckles compared to the nucleoplasm, particularly chromatin- and nucleus-associated transcripts. While total polyadenylated RNA retention increased with greater nuclear speckle cohesion, the ratios of most mRNA species to each other were constant, indicating non-selective, or proportional, retention. We then explored whether nuclear speckle cohesion changes in response to environmental perturbations associated with changes in kinase or phosphatase activity. We found that cellular responses to heat shock, oxidative stress, and hypoxia include changes to the cohesion of nuclear speckles and mRNA retention. Our results demonstrate that tuning the material properties of nuclear speckles provides a mechanism for the acute control of mRNA localization.
2024-11-10 | GSE240883 | GEO
Project description:Prior work revealed nuclear-localized aminoacyl-tRNA synthetases (aaRSs) that checked newly synthesized tRNAs for charging before export to the cytoplasm. To reveal other functions, we sought to identify nuclear proteins that interact with arginyl-tRNA synthetase (ArgRS) in the nucleus. Serine/Arginine Repetitive Matrix Protein 2 (SRRM2), which is stored with RNA splicing apparatus components in nuclear speckle condensates, was found as a consistent interaction partner that co localized with SRRM2 ArgRS in nuclear speckles. Dynamic photo-bleaching experiments showed that, consistent with condensate properties, SRRM2 has a fluctuating appearance in speckles. Knock down of ArgRS impeded SRRM2 speckle trafficking and, coincidently, altered splicing processing of pre-mRNA transcripts. Among the altered spliced variants, those of tRNA synthetase family members were prominent. Thus, nuclear ArgRS shapes the dynamics of a protein in class of nuclear condensates. Also, the work expands the repertoire of nuclear tRNA synthetase roles to include regulation of RNA splicing, including of aaRS family member transcripts.
2023-04-14 | PXD015692 | Pride
Project description:MALAT-1 is a long mammalian non-coding transcript of approximately 8500 nucleotides. It is localized to nuclear speckles despite its mRNA-like characteristics, which usually result in the export of transcripts to the cytoplasm. In the present study, we report the identification of several factors that influence the nuclear speckle localization of MALAT-1, and we provide evidence that MALAT-1 is involved in the regulation of gene expression. Heterokaryon assays revealed that MALAT-1 does not shuttle between the nucleus and cytoplasm, but is stably retained within the nucleus. Analysis of MALAT-1 fragments showed that MALAT-1 contains two distinct nuclear speckle-directing elements (between nucleotides 1961 to 3040 and 6008 to 7011 of the MALAT-1 sequence). The knockdown of the nuclear speckle proteins, RNPS1, SRm160 or IBP160, resulted in the diffusion of MALAT-1 to the nucleoplasm. In addition, we have demonstrated that depletion of MALAT-1 represses the expression of several genes. This repression of gene expression also occurs in response to the delocalization of MALAT-1 from the nuclear speckles. These results suggest that RNPS1, SRm160 and IBP160 contribute to the localization of MALAT-1 to nuclear speckles where it is involved in regulating gene expression
2010-06-02 | GSE20506 | GEO
Project description:The nucleus is highly organized such that factors involved in transcription and processing of distinct classes of RNA are organized within specific nuclear bodies. One example is the nuclear speckle, which is defined by high concentrations of protein and non-coding RNA regulators of pre-mRNA splicing. What functional role, if any, speckles might play in the process of mRNA splicing remains unknown. Here we show that genes localized near nuclear speckles display higher spliceosome concentrations, increased spliceosome binding to their pre-mRNAs, and higher co-transcriptional splicing levels relative to genes that are located farther from nuclear speckles. We show that directed recruitment of a pre-mRNA to nuclear speckles is sufficient to increase mRNA splicing levels. Finally, we show that gene organization around nuclear speckles is highly dynamic with differential localization between cell types corresponding to differences in splicing efficiency. Together, our results integrate the longstanding observations of nuclear speckles with the biochemistry of mRNA splicing and demonstrate a critical role for dynamic 3D spatial organization of genomic DNA in driving spliceosome concentrations and controlling the efficiency of mRNA splicing.
2024-03-22 | GSE247833 | GEO
Project description:Dynamics of RNA localization to nuclear speckles are connected to splicing efficiency [ARTR-seq]
| PRJNA1073947 | ENA
Project description:Nuclear speckles are dynamic nuclear bodies characterized by high local concentrations of RNA binding proteins and specific non-coding RNAs. Although the contents of speckles suggest multifaceted roles in regulating chromatin dynamics and gene expression, the overarching biological function(s) of nuclear speckles remain enigmatic. In this study, we investigate speckle compositional variation in human cancer, finding two main speckle compositional states based on RNA expression of speckle-resident proteins. One cancer speckle state was more similar to normal adjacent tissues, while the other was dissimilar from normal tissue, and thus considered an aberrant cancer speckle state. We link the aberrant speckle state to altered speckle positioning within the nucleus, to elevation of the TREX RNA export complex, and to worse patient outcomes in clear cell renal cell carcinoma (ccRCC). ccRCC is typified by hyperactivation of the HIF-2a transcription factor, and we demonstrate that HIF-2a drives physical association of a select subset of its target genes with nuclear speckles depending on HIF-2a's two speckle targeting motifs (STMs) defined in this study. STMs are highly enriched among transcription factors, suggesting that DNA-speckle targeting may be a general mechanism of gene regulation and providing a resource of candidate speckle-targeting factors. Via integration of tissue culture functional studies with tumor genomic and imaging analysis, we show that HIF-2a gene regulatory programs are impacted by speckle compositional state and by abrogation of speckle targeting abilities of HIF-2a. These findings suggest that, in ccRCC, a key biological function of nuclear speckles is to modulate expression of a specific subset of HIF-2a-regulated target genes that, in turn, influence patient outcomes. Beyond ccRCC, tumor speckle compositional states broadly correlate with altered functional pathways and expression of speckle-associated gene neighborhoods, exposing a general link between nuclear speckles and gene expression dysregulation in human cancer.
2024-09-03 | GSE248710 | GEO
Project description:Nuclear speckles are dynamic nuclear bodies characterized by high local concentrations of RNA binding proteins and specific non-coding RNAs. Although the contents of speckles suggest multifaceted roles in regulating chromatin dynamics and gene expression, the overarching biological function(s) of nuclear speckles remain enigmatic. In this study, we investigate speckle compositional variation in human cancer, finding two main speckle compositional states based on RNA expression of speckle-resident proteins. One cancer speckle state was more similar to normal adjacent tissues, while the other was dissimilar from normal tissue, and thus considered an aberrant cancer speckle state. We link the aberrant speckle state to altered speckle positioning within the nucleus, to elevation of the TREX RNA export complex, and to worse patient outcomes in clear cell renal cell carcinoma (ccRCC). ccRCC is typified by hyperactivation of the HIF-2a transcription factor, and we demonstrate that HIF-2a drives physical association of a select subset of its target genes with nuclear speckles depending on HIF-2a's two speckle targeting motifs (STMs) defined in this study. STMs are highly enriched among transcription factors, suggesting that DNA-speckle targeting may be a general mechanism of gene regulation and providing a resource of candidate speckle-targeting factors. Via integration of tissue culture functional studies with tumor genomic and imaging analysis, we show that HIF-2a gene regulatory programs are impacted by speckle compositional state and by abrogation of speckle targeting abilities of HIF-2a. These findings suggest that, in ccRCC, a key biological function of nuclear speckles is to modulate expression of a specific subset of HIF-2a-regulated target genes that, in turn, influence patient outcomes. Beyond ccRCC, tumor speckle compositional states broadly correlate with altered functional pathways and expression of speckle-associated gene neighborhoods, exposing a general link between nuclear speckles and gene expression dysregulation in human cancer.
2024-09-03 | GSE248705 | GEO