Project description:Biomolecular condensates composed of proteins and RNA are one approach by which cells regulate post-transcriptional gene expression. Their formation typically involves the phase separation of intrinsically disordered proteins with a target mRNA, sequestering the mRNA into a liquid condensate. This sequestration regulates gene expression by modulating translation or facilitating RNA processing. Here, we engineer synthetic condensates using a fusion of an RNA-binding protein, the human Pumilio2 homology domain, and a synthetic intrinsically disordered protein, an elastin-like polypeptide, that can bind and sequester a target mRNA transcript. In protocells, sequestration of a target mRNA largely limits its translation. Conversely, in E. Coli, sequestration of the same target mRNA increases its translation. We characterize the Pum2-ELP condensate system using microscopy, biophysical and biochemical assays, and RNA-seq. This approach enables modulation of cell function via the formation of synthetic biomolecular condensates that upregulate the expression of a target protein.
Project description:Protein aggregation is a complex phenomenon involving aberrant folding and proteostasis that leads to various proteopathies. Despite extensive efforts, the maintenance of protein solubility against aggregation remains ill-defined, especially in complex cellular environments. In this study, we show that the depletion of RNAs from Escherichia coli lysates results in global protein aggregation. Using quantitative mass spectroscopic analysis, we identified significant proteins (>900) from the whole E. coli proteome whose solubility maintenance is dependent on RNA. Proteome-wide characterization revealed that RNA dependence was highly enriched among acidic proteins, intrinsically disordered proteins, and structural hub proteins. Notably, the solubility of representative molecular chaperones [Trigger factor (TF), DnaJ, and GroES] is largely dependent on RNA, suggesting a hitherto unknown hierarchical relationship between RNA-based chaperone (chaperna) and protein-based molecular chaperones. Our findings provide new insights into proteome solubility maintenance and misfolding-associated proteopathy in vivo, where proteins, from birth to death, stably or transiently associate with RNAs.
Project description:NUP98-fusion proteins cause acute myeloid leukemia via unknown molecular mechanisms. All NUP98-fusion proteins share an intrinsically disordered region (IDR) featuring >35 repeats of Phenylalanine-Glycine (FG) in the NUP98 N-terminus. Conversely, different C-terminal NUP98-fusion partners are often transcriptional and epigenetic regulators. Given these structural features we hypothesized that mechanisms of oncogenic transformation by NUP98-fusion proteins are hard-wired in their protein interactomes. Affinity purification coupled to mass spectrometry of five distinct NUP98-fusion proteins revealed a conserved set of interactors that was highly enriched for proteins involved in biomolecular condensation. We developed biotinylated isoxazole-mediated condensome mass spectrometry (biCon-MS) to show that NUP98-fusion proteins alter the global composition of biomolecular condensates. In addition, an artificial FG-repeat containing fusion protein was able to phenocopy the induction of leukemic gene expression as mediated by NUP98-KDM5A. Thus, we propose that IDR-containing fusion proteins have evolved to uniquely combine biomolecular condensation with gene control to induce cancer.
Project description:Intrinsically disordered regions (IDRs) in DNA-associated proteins have recently been shown to play important roles in gene regulation. To better understand these domains we developed an antibody-independent assay to map disordered proteins genome-wide by combining b-isox mediated precipitation and next-generation sequencing (DisP-seq, disordered protein precipitation followed by DNA sequencing). We first analyzed Ewing sarcoma cells as a proof of principle given that the prion-like IDR of the oncogenic fusion protein EWS-FLI1 has been shown to play a critical role in this cancer. We find that DisP-seq produces thousands of strong peaks associated with diverse chromatin states in Ewing sarcoma and other cell types tested. These locations are highly enriched for DNA binding motifs matching EWS-FLI1 and other transcription factors with prominent IDRs. Moreover, depletion of EWS-FLI1 in Ewing sarcoma cells leads to a widespread reorganization of DisP-seq signals, including decreases at EWS-FLI1 binding sites and marked increases at sites associated with mesenchymal differentiation. Analysis of these new DisP-seq signals shows that they arise from redistribution of the transcription factor NFIB, which initially overlaps EWS-FLI1 and has an IDR that is required for proper localization and function. Our results thus show that antibody-independent precipitation mapping can enable genome-wide profiling and identification of disordered transcription factors to uncover their roles in complex gene regulation programs.
Project description:Intrinsically disordered regions (IDRs) in DNA-associated proteins have recently been shown to play important roles in gene regulation. To better understand these domains we developed an antibody-independent assay to map disordered proteins genome-wide by combining b-isox mediated precipitation and next-generation sequencing (DisP-seq, disordered protein precipitation followed by DNA sequencing). We first analyzed Ewing sarcoma cells as a proof of principle given that the prion-like IDR of the oncogenic fusion protein EWS-FLI1 has been shown to play a critical role in this cancer. We find that DisP-seq produces thousands of strong peaks associated with diverse chromatin states in Ewing sarcoma and other cell types tested. These locations are highly enriched for DNA binding motifs matching EWS-FLI1 and other transcription factors with prominent IDRs. Moreover, depletion of EWS-FLI1 in Ewing sarcoma cells leads to a widespread reorganization of DisP-seq signals, including decreases at EWS-FLI1 binding sites and marked increases at sites associated with mesenchymal differentiation. Analysis of these new DisP-seq signals shows that they arise from redistribution of the transcription factor NFIB, which initially overlaps EWS-FLI1 and has an IDR that is required for proper localization and function. Our results thus show that antibody-independent precipitation mapping can enable genome-wide profiling and identification of disordered transcription factors to uncover their roles in complex gene regulation programs.
Project description:Intrinsically disordered regions (IDRs) in DNA-associated proteins have recently been shown to play important roles in gene regulation. To better understand these domains we developed an antibody-independent assay to map disordered proteins genome-wide by combining b-isox mediated precipitation and next-generation sequencing (DisP-seq, disordered protein precipitation followed by DNA sequencing). We first analyzed Ewing sarcoma cells as a proof of principle given that the prion-like IDR of the oncogenic fusion protein EWS-FLI1 has been shown to play a critical role in this cancer. We find that DisP-seq produces thousands of strong peaks associated with diverse chromatin states in Ewing sarcoma and other cell types tested. These locations are highly enriched for DNA binding motifs matching EWS-FLI1 and other transcription factors with prominent IDRs. Moreover, depletion of EWS-FLI1 in Ewing sarcoma cells leads to a widespread reorganization of DisP-seq signals, including decreases at EWS-FLI1 binding sites and marked increases at sites associated with mesenchymal differentiation. Analysis of these new DisP-seq signals shows that they arise from redistribution of the transcription factor NFIB, which initially overlaps EWS-FLI1 and has an IDR that is required for proper localization and function. Our results thus show that antibody-independent precipitation mapping can enable genome-wide profiling and identification of disordered transcription factors to uncover their roles in complex gene regulation programs.
Project description:San1 is an E3 ubiquitin ligase involved in nuclear protein quality control via its interaction with intrinsically disordered proteins for ubiquitylation and 26S proteasomal degradation. Since a number of transcription/chromatin regulatory factors contain intrinsically disordered domains and can be inhibitory to transcription when in excess, San1 might be involved in regulation of transcription. To address this, we carried out ChIP-seq (Chromatin immunoprecipitation sequencing) here to analyze the role of San1 in genome-wide association of TBP (TATA-box binding protein that nucleates the preinitiation complex formation at the promoter for transcription initiation) and RNA polymerase II (that is recruited to the promoter by TBP and subsequently engaged in transcription elongation at the coding sequence for mRNA biosynthesis). Our results reveal the genome-wide role of San1 in facilitating the recruitment of TBP to the promoter, thus indicating its involvement in promoting the preinitiation complex formation for transcription initiation. Further, we find the global role of San1 in regulating RNA polymerase II at the coding sequence.
Project description:Disordered regions within RNA binding proteins are required to control mRNA decay and protein synthesis. To understand how these disordered regions modulate gene expression, we surveyed regulatory activity across the entire disordered proteome using a high-throughput functional assay. We identified hundreds of regulatory sequences within intrinsically disordered regions and demonstrate how these elements cooperate with core mRNA decay machinery to promote transcript turnover. Coupling high-throughput functional profiling with mutational scanning revealed diverse molecular features, ranging from defined motifs to overall sequence composition, underlying the regulatory effects of disordered peptides. Machine learning analysis implicated aromatic residues in particular contexts as critical determinants of repressor activity, consistent with their roles in forming protein-protein interactions with downstream effectors. Our results define the molecular principles and biochemical mechanisms that govern post-transcriptional gene regulation by disordered regions and exemplify the encoding of diverse yet specific functions in the absence of well-defined structure.
Project description:Aberrant formation of biomolecular condensates has been proposed to play a role in several cancers. The oncogenic fusion protein BRD4-NUT forms condensates and drives changes in gene expression in Nut Carcinoma (NC). Here we sought to understand the molecular elements of BRD4-NUT and its associated histone acetyltransferase (HAT), p300, that promote these activities. We determined that a minimal fragment of NUT (MIN) in fusion with BRD4 is necessary and sufficient to bind p300 and form condensates. Furthermore, a BRD4-p300 fusion protein also forms condensates and drives gene expression similarly to BRD4-NUT(MIN), suggesting the p300 fusion may mimic certain features of BRD4-NUT. The intrinsically disordered regions, transcription factor-binding domains, and HAT activity of p300 all collectively contribute to condensate formation by BRD4-p300, suggesting that these elements might contribute to condensate formation by BRD4-NUT. Conversely, only the HAT activity of BRD4-p300 appears necessary to mimic the transcriptional profile of cells expressing BRD4-NUT. Our results suggest a model for condensate formation by the BRD4-NUT:p300 complex involving a combination of positive feedback and phase separation, and show that multiple overlapping, yet distinct, regions of p300 contribute to condensate formation and transcriptional regulation.
Project description:HIPPO-YAP/TAZ signaling has been implicated in supratentorial ependymoma formation from neural progenitor cells (NPC) in the brain, however, the underlying mechanisms to trigger the neural progenitor cell transformation remains elusive. Here, we uncover that patient-derived tumorigenic YAP-fusion proteins (YAP-MAMLD1 and C11ORF95-YAP) promote ependymoma tumorigenesis through forming liquid-liquid phase-separated condensates. Intrinsically disordered regions (IDR) in the fusion proteins promote oligomerization of YAP-transcriptional co-activators and self-assembly of nuclear puncta-like membrane-less organelles. Phase separation of YAP-fusion proteins further facilitates the compartmentalization of transcriptional coactivators, BRD4 and MED1, resulting in pervasive enhancer landscape changes and exclusion of transcriptional repressors such as PRC2 complexes. YAP-fusion proteins-induced nuclear puncta recruit RNA polymerase II to promote transcriptional bursting of multiple oncogenic pathways. Moreover, we show that IDR-mediated phase separation is necessary for YAP-fusion protein-induced tumor formation. Distinct YAP fusion-proteins identified in other human tumors also encompass IDR features. Together, our data suggest that IDR-mediated phase separation is an integral component of YAP-fusion protein-induced tumorigenesis and might serve as a therapeutic target in supratentorial ependymoma.