Effect of CLK2 expression in the regulation of intron retention during heat shock [RNA-seq]
Ontology highlight
ABSTRACT: Intron retention (IR) constitutes a less explored form of alternative splicing, wherein introns are retained within mature mRNA transcripts. Our investigation demonstrates that the CDC-like kinase 2 (CLK2) undergoes liquid-liquid phase separation (LLPS) within nuclear speckles in response to heat shock (HS). The formation of CLK2 condensates depends on the intrinsically disordered region (IDR) located within the N-terminal amino acids 1-148. Phosphorylation at residue T343 sustains CLK2 kinase activity and facilitates autophosphorylation, thus inhibiting the LLPS activity of the IDR. These CLK2 condensates initiate the reorganization of nuclear speckles, transforming them into larger, rounded structures. Moreover, these condensates facilitate the recruitment of splicing factors into these compartments, potentially restricting their access to mRNA for intron splicing. Consequently, the formation of CLK2 condensates promotes the IR.
Project description:Our results show that CLK2 undergoes liquid-liquid phase separation (LLPS) in response to heat shock stress. Phosphorylation of CLK2 at T343 prevents the LLPS of CLK2. To identify the proteins that recruited to the CLK2 condensates, we immunoprecipitated CLK2 (WT) or (T343A) proteins with FLAG antibody and performed mass spectrometry to detect the interacting proteins.
Project description:Nuclear speckles (NSs) are nuclear biomolecular condensates that are postulated to arise through liquid-liquid phase separation (LLPS), although the detailed underlying forces driving NS formation remain elusive. SRRM2 and SON are 2 non-redundant scaffold proteins for NSs. How each individual protein governs assembly of NS protein network and the functional relationship between SRRM2 and SON are largely unknown. Here, we uncover immiscible multiphase of SRRM2 and SON within NSs. SRRM2 and SON are functionally independent, specifically regulating alternative splicing of subsets of mRNA targets, respectively. We further uncover that SRRM2 forms multicomponent liquid phase in cells to drive NS subcompartmentalization, which is reliant on homotypic interaction and heterotypic non-selective protein-RNA complex coacervation-driven multicomponent LLPS. SRRM2 RS domains form high-order oligomers, and can be replaced by oligomerizable synthetic modules, the serine residues within the RS domains, however, play an irreplaceable role in fine-tuning the liquidity of NSs.
Project description:Little is known about the regulation and function of liquid‒liquid phase separation (LLPS) in craniofacial developmental disorders, where Msh homeobox 1 (MSX1) and protein arginine methyltransferase 1 (PRMT1) are two important regulators. MSX1 mutations are associated with human cleft palate, the most common craniofacial birth defect. Here, we show that MSX1 LLPS, regulated by PRMT1-catalyzed methylation, is a vertebrate-conserved mechanism underlying the proliferation of embryonic palatal mesenchymal cells (EPMs) and palatal fusion. MSX1 LLPS is triggered by its N-terminal intrinsically disordered protein region (IDR) and regulated by PRMT1-catalyzed methylation, specifically asymmetric dimethylation of arginine (R). Biochemically, PRMT1 methylates MSX1 by dimethylating the residues R150 and R157 in the MSX1 IDR. Physiochemically, the R157 to serine (R157S) mutant, R150S mutant, and hypomethylated MSX1 under PRMT1 deficiency consistently cause abnormal MSX1 LLPS to form less dynamic gel-like condensates. PRMT1 and its methylation target R residues in MSX1 are conserved in vertebrates, from zebrafish to humans. Phenotypically, less dynamic gel-like condensates formed by abnormal MSX1 LLPS cause EPM proliferation defects and cleft palate.In this study, rna-seq was used to reveal the differences between the effects of Msx1 and its mutants on hepm cells. Our findings provide a new paradigm for further exploration of LLPS underlying genetic disorders for future innovation of genetic disorder treatment by direct modulation of LLPS.
Project description:Development of cancer is intimately associated with genetic abnormalities that target proteins with intrinsically disordered regions (IDRs). In human hematological malignancies, recurrent chromosomal translocation of nucleoporin (NUP98 or NUP214) generates an aberrant chimera that invariably retains nucleoporin?s IDR, tandemly dispersed phenylalanine-and-glycine (FG) repeats. However, it remains elusive how unstructured IDRs contribute to oncogenesis. We show that IDR harbored within NUP98-HOXA9, a homeodomain-containing transcription factor (TF) chimera recurrently detected in leukemias, is essential for establishing liquid-liquid phase separation (LLPS) puncta of chimera and for inducing leukemic transformation. Strikingly, LLPS of NUP98-HOXA9 not only promotes chromatin occupancy of chimera TFs but is also required for formation of a broad, ?super-enhancer?-like binding pattern, typically seen at a battery of leukemogenic genes, potentiating their transcriptional activation. Artificial HOX chimera (FUS-HOXA9), created by replacing NUP98?s FG repeats with an unrelated LLPS-forming IDR of FUS, had similar enhancement effects on chimera?s genome-wide binding and target gene activation. Hi-C mapping further demonstrated that phase-separated NUP98-HOXA9 induces CTCF-independent chromatin looping enriched at proto-oncogenes. Together, this report describes a proof-of-principle example wherein cancer acquires mutation to establish oncogenic TF condensates via phase separation, which simultaneously enhances their genomic targeting and induces organization of aberrant three-dimensional chromatin structure during tumorous transformation. As LLPS-competent molecules are frequently implicated in diseases, this mechanism can potentially be generalized to many malignant and pathological settings.
Project description:Development of cancer is intimately associated with genetic abnormalities that target proteins with intrinsically disordered regions (IDRs). In human hematological malignancies, recurrent chromosomal translocation of nucleoporin (NUP98 or NUP214) generates an aberrant chimera that invariably retains nucleoporin?s IDR, tandemly dispersed phenylalanine-and-glycine (FG) repeats. However, it remains elusive how unstructured IDRs contribute to oncogenesis. We show that IDR harbored within NUP98-HOXA9, a homeodomain-containing transcription factor (TF) chimera recurrently detected in leukemias, is essential for establishing liquid-liquid phase separation (LLPS) puncta of chimera and for inducing leukemic transformation. Strikingly, LLPS of NUP98-HOXA9 not only promotes chromatin occupancy of chimera TFs but is also required for formation of a broad, ?super-enhancer?-like binding pattern, typically seen at a battery of leukemogenic genes, potentiating their transcriptional activation. Artificial HOX chimera (FUS-HOXA9), created by replacing NUP98?s FG repeats with an unrelated LLPS-forming IDR of FUS, had similar enhancement effects on chimera?s genome-wide binding and target gene activation. Hi-C mapping further demonstrated that phase-separated NUP98-HOXA9 induces CTCF-independent chromatin looping enriched at proto-oncogenes. Together, this report describes a proof-of-principle example wherein cancer acquires mutation to establish oncogenic TF condensates via phase separation, which simultaneously enhances their genomic targeting and induces organization of aberrant three-dimensional chromatin structure during tumorous transformation. As LLPS-competent molecules are frequently implicated in diseases, this mechanism can potentially be generalized to many malignant and pathological settings.
Project description:We found that CPSF6, a component of the CFIm, can form liquid-liquid phase separation (LLPS) and the elevated LLPS induces the preferential usage of the distal poly(A) sites. CLK2, a kinase upregulated in cancer cells, destructs LLPS of CPSF6 by phosphorylating its arginine/serine-like domain. Albeit higher expression of CPSF6 in cancer, the reduction of LLPS leads to shortening 3’ UTR of cell cycle related genes and then promotes cell proliferation. These results reveal that LLPS regulation of CPSF6 is a fine tuning way of APA in cancer cells and provide a new mechanism for APA regulation by regulating LLPS of 3’ end processing factors through post-translational modification.
Project description:We established the HeLa cells expressing the GFP (control) or CLK2 (T343A) with deletion of the IDR [T343A (dIDR)]. These cells were subjected to RNA-seq for the alternative splicing analysis.
Project description:TFIID is an essential eukaryotic transcription factor, which is required for RNA polymerase II promoter recognition and activation. As a multiprotein complex, TFIID contains several intrinsically disordered regions (IDRs), but the functions of these IDRs are unknown. Here, we show that a conserved IDR drives the TFIID subunit TAF2 to nuclear speckles, where it forms biomolecular condensates, separate from the TFIID complex. Quantitative mass spectrometry analyses reveal that the TAF2 IDR is required for the interaction with the nuclear speckle and spliceosome-associated protein SRRM2, which is thereby recruited to TFIID. The formation of SRRM2-free TFIID complexes elicits a set of unique alternative splicing events. These include events in RNAs coding for proteins involved in transcription and transmembrane transport. Together, these data identify an IDR of the basal transcription machinery as a molecular switch between nuclear compartments to control protein complex composition and pre-mRNA splicing.
Project description:Liquid-liquid phase separation (LLPS) has emerged as a central paradigm for understanding how membrane-less organelles compartmentalize diverse cellular activities in eukaryotes. Here, we identified a new superfamily of plant Guanylate Binding Protein-Like GTPases (GBPLs) that assemble LLPS-driven condensates within the nucleus to protect against infection and autoimmunity. In Arabidopsis thaliana, two family members - GBPL1 and GBPL3 - undergo phase transition behavior to control transcriptional responses as part of an allosteric switch triggered by exposure to biotic stress. GBPL1, a pseudoGTPase, sequesters catalytically-active GBPL3 under basal conditions but is displaced by LLPS when GBPL3 enters the nucleus following immune cues to drive formation of unique membrane-less organelles termed GDACs (GBPL Defense-Activated Condensates) that we visualized by in situ cryo-electron tomography. Within these mesoscale GDAC structures, native GBPL3 directly bound defense gene promoters and recruited specific transcriptional coactivators of the Mediator complex plus RNA Pol II machinery to massively reprogram host gene expression for disease resistance. Together, our study identifies a new GBPL circuit that reinforces the biological importance of phase-separated condensates, in this case, as indispensable players in plant defense.
Project description:Some transcription factors (TFs) can form liquid-liquid phase separated (LLPS) condensates. However, the function of these TF condensates in 3D genome organization and gene regulation remains elusive. In response to methionine (met) starvation in budding yeast, Met4 and a few sequence-specific co-activators, including Met32, induce a set of genes involved in met biosynthesis. Here, we show that the endogenous Met4 and Met32 form puncta-like structures that significantly overlap in yeast nuclei upon met depletion. Recombinant Met4 and Met32 form mixed droplets with LLPS properties in vitro. In relation to chromatin, Met4 puncta co-localize with target genes, and at least a subset of these target genes are clustered in 3D in a Met4-dependent manner. A MET3pr-GFP reporter inserted near several native Met4 binding sites becomes co-localized with Met4 puncta and displays enhanced transcriptional activity. A Met4 variant with a partial truncation of an intrinsically disordered region (IDR) shows less puncta formation, and this mutant selectively reduces the reporter activity near Met4 binding sites to the basal level. Overall, these results support a model where Met4 and co-activators form condensates to bring multiple target genes into a vicinity with higher local TF concentrations, which facilitates a strong response to met depletion (-met).