The intrinsically disordered TSSC4 protein acts as a helicase inhibitor, placeholder and multi-interaction coordinator during snRNP assembly and recycling
Ontology highlight
ABSTRACT:
ORGANISM(S): Homo sapiens
PROVIDER: GSE185418 | GEO | 2022/01/17
REPOSITORIES: GEO
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Project description:The intrinsically disordered TSSC4 protein acts as a helicase inhibitor, placeholder and multi-interaction coordinator during snRNP assembly and recycling
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Project description:Protein conformation dictates a great deal of protein function. A class of naturally unstructured proteins, termed intrinsically disordered proteins (IDPs), demonstrates that flexibility in structure can be as important mechanistically as rigid structure. At the core of the circadian transcription/translation feedback loop in Neurospora crassa is the protein FREQUENCY (FRQ), shown here shown to share many characteristics of IDPs. FRQ in turn binds to FREQUENCY-Interacting RNA Helicase (FRH), whose clock function has been assumed to relate to its predicted helicase function. However, mutational analyses reveal that the helicase function of FRH is not essential for the clock, and a region of FRH distinct from the helicase region is essential for stabilizing FRQ against rapid degradation via a pathway distinct from its typical ubiquitin-mediated turnover. These data lead to the hypothesis that FRQ is an IDP and that FRH acts nonenzymatically, stabilizing FRQ to enable proper clock circuitry/function.
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Project description:RNA helicases—central enzymes in RNA metabolism— often feature intrinsically disordered regions (IDRs) that enable phase separation and complex interactions with other proteins and/or RNA molecules. IDRs are varied and fast evolving, which makes their function hard to predict. In the bacterial pathogen Pseudomonas aeruginosa, two non-redundant RNA helicases, RhlE1 and RhlE2, share a conserved REC catalytic core but have different C-terminal extensions (CTEs) composed of IDRs of diverse length and amino acid composition. Here, we show how the IDR diversity defines RhlE RNA helicase specificity of function. Both CTEs facilitate RNA binding and phase separation in vitro, leading to the in vivo localization of proteins in clusters within the cytoplasm. However, the CTE of RhlE2 is more efficient in enhancing REC core RNA unwinding, exhibits a greater tendency for phase separation, and interacts with the RNase E endonuclease, a crucial player in mRNA degradation. Swapping CTEs results in chimeric proteins that are biochemically active but functionally distinct as compared to their native counterparts. The RECRhlE1-CTERhlE2 chimera improves cold growth of a rhlE1 mutant, gains interaction with RNase E and affects a subset of both RhlE1 and RhlE2 RNA targets. The RECRhlE2-CTERhlE1 chimera instead hampers bacterial growth at low temperatures in the absence of RhlE1, with its detrimental effect linked to aberrant RNA droplets. By showing that IDRs modulate both protein core activities and subcellular localization, our study defines the impact of IDR diversity on the functional differentiation of RNA helicases.
2024-05-30 | GSE253333 | GEO
Project description:Precursor messenger RNA splicing is mediated by the spliceosome, a large and dynamic molecular machine composed of five small nuclear RNAs and numerous proteins. Many spliceosomal proteins are predicted to be intrinsically disordered or contain large disordered regions, but experimental validation of these predictions is scarce, and the precise functions of these proteins are often unclear. Here, we show via circular dichroism spectroscopy, dynamic light scattering, and NMR spectroscopy that the yeast spliceosomal disassembly factor Ntr2 is largely intrinsically disordered. Peptide SPOT analyses, analytical size-exclusion chromatography, and surface plasmon resonance measurements revealed that Ntr2 uses an N-terminal region to bind the C-terminal helicase unit of the Brr2 RNA helicase, an enzyme involved in spliceosome activation and implicated in splicing catalysis and spliceosome disassembly. NMR analyses suggested that Ntr2 does not adopt a tertiary structure and likely remains disordered upon complex formation. RNA binding and unwinding studies showed that Ntr2 downregulates Brr2 helicase activity in vitro by modulating the fraction of helicase molecules productively bound to the RNA substrate. Our data clarify the nature of a physical link between Brr2 and Ntr2, and point to the possibility of a functional Ntr2-Brr2 interplay during splicing.
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Project description:The RNA helicase BRR2 (SNRNP200) is one of the key remodeling factors of the spliceosome. Here we show its direct interaction with C9ORF78, a poorly characterized protein predicted to be largely intrinsically disordered. We present cryo-EM structures showing how C9ORF78 and the spliceosomal B-complex protein FBP21 wrap around the C-terminal helicase cassette of BRR2 and that binding of the two proteins is mutually exclusive. C9ORF78 associates with the spliceosome, as we confirm via proteomics and RNA UV-crosslinking. An siRNA mediated C9ORF78 knockdown reveals changes in alternative splicing of specific target pre-mRNAs, which in part depend on its interaction with BRR2. In particular, C9ORF78 regulates a substantial number of alternative 3’ splice sites, which might be facilitated through an additional interaction with human PRP22 (DHX8).
2021-12-31 | GSE176517 | GEO
Project description:The RNA helicase BRR2 (SNRNP200) is one of the key remodeling factors of the spliceosome. Here we show its direct interaction with C9ORF78, a poorly characterized protein predicted to be largely intrinsically disordered. We present cryo-EM structures showing how C9ORF78 and the spliceosomal B-complex protein FBP21 wrap around the C-terminal helicase cassette of BRR2 and that binding of the two proteins is mutually exclusive. C9ORF78 associates with the spliceosome, as we confirm via proteomics and RNA UV-crosslinking. An siRNA mediated C9ORF78 knockdown reveals changes in alternative splicing of specific target pre-mRNAs, which in part depend on its interaction with BRR2. In particular, C9ORF78 regulates a substantial number of alternative 3’ splice sites, which might be facilitated through an additional interaction with human PRP22 (DHX8).
2021-12-31 | GSE189362 | GEO
Project description:The RNA helicase BRR2 (SNRNP200) is one of the key remodeling factors of the spliceosome. Here we show its direct interaction with C9ORF78, a poorly characterized protein predicted to be largely intrinsically disordered. We present cryo-EM structures showing how C9ORF78 and the spliceosomal B-complex protein FBP21 wrap around the C-terminal helicase cassette of BRR2 and that binding of the two proteins is mutually exclusive. C9ORF78 associates with the spliceosome, as we confirm via proteomics and RNA UV-crosslinking. An siRNA mediated C9ORF78 knockdown reveals changes in alternative splicing of specific target pre-mRNAs, which in part depend on its interaction with BRR2. In particular, C9ORF78 regulates a substantial number of alternative 3’ splice sites, which might be facilitated through an additional interaction with human PRP22 (DHX8).
2022-02-04 | GSE176464 | GEO
Project description:Carboxysomes are a paradigm of self-assembling proteinaceous organelles found in nature, offering compartmentalisation of enzymes and pathways to enhance carbon fixation. In α-carboxysomes, the disordered linker protein CsoS2 plays an essential role in carboxysome assembly and Rubisco encapsulation. Its mechanism of action, however, is not fully understood. Here we synthetically engineer α-carboxysome shells using minimal shell components and determine cryoEM structures of these to decipher the principle of shell assembly and encapsulation. The structures reveal that the intrinsically disordered CsoS2 C-terminus is well-structured and acts as a universal "molecular thread" stitching through multiple shell protein interfaces. We further uncover in CsoS2 a highly conserved repetitive key interaction motif, [IV]TG, which is critical to the shell assembly and architecture. Our study provides a general mechanism for the CsoS2-governed carboxysome shell assembly and cargo encapsulation and further advances synthetic engineering of carboxysomes for diverse biotechnological applications.
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Project description:Metazoans employ chromodomain helicase DNA-binding (CHD) enzymes to reposition nucleosomal DNA for transcription and replication. The CHD family consists of nine distinct members (CHD1-9) that possess highly conserved chromo and ATPase domains. These domains are flanked by poorly characterised N- and C-termini, which are enriched with intrinsically disordered regions (IDRs) and short aggregation-prone regions (APRs). The contribution of IDRs and APRs to CHD function has remained elusive. In this study we used affinity purification followed by mass spectrometry analysis (AP-MS) to define the protein-protein interaction (PPI) networks within the N- and C-termini of each CHD family member. The results illustrate a comprehensive map of CHD1-9-specific binding proteins that include dozens of novel interactions with transcription regulators and epigenetic factors. Using AlphaFold Multimer we examined the structural predictions of high confidence PPIs from our AP-MS screens and identified APR regions with alpha helical structures that contribute to PPIs. We further investigated a highly conserved APR within the C-terminus of the CHD4 protein and demonstrate that it contributes to the interaction of CHD4 with the nucleosome remodelling and deacetylase (NuRD) and CHD, ADNP, HP1 (ChAHP) complexes. Peptides mimicking this APR effectively disrupt CHD4 binding to both NuRD and ChAHP complexes, consequently triggering the transcriptional activation or repression of hundreds of target genes. Our results emphasise the crucial role that the N- and C-termini of CHD chromatin remodelers play in establishing protein-protein interaction (PPI) networks, which drive unique transcriptional programs.
2025-01-01 | GSE275475 | GEO
Project description:The innate immune receptor RIG-I provides a first line of defense against viral infections. Viral RNAs are recognized by RIG-I's C-terminal domain (CTD), but the RNA must engage the helicase domain to release the signaling CARD (Caspase Activation and Recruitment Domain) domains from their autoinhibitory CARD2:Hel2i interactions. Because the helicase itself lacks RNA specificity, mechanisms to proofread RNAs entering the helicase domain must exist. Although such mechanisms would be crucial in preventing aberrant immune responses by non-specific RNAs, they remain largely uncharacterized to date. This study reveals a previously unknown proofreading mechanism through which RIG-I ensures that the helicase engages RNAs explicitly recognized by the CTD. A crucial part of this mechanism involves the intrinsically disordered CARDs-Helicase Linker (CHL), which connects the CARDs to the helicase subdomain Hel1. CHL uses its negatively charged regions to antagonize incoming RNAs electrostatically. In addition to this RNA gating function, CHL is essential for stabilization of the CARD2:Hel2i interface. Overall, we uncover that the CHL and CARD2:Hel2i interface work together to establish a tunable gating mechanism that allows CTD-chosen RNAs to bind the helicase domain, while at the same time blocking non-specific RNAs. These findings also indicate that CHL could represent a novel target for RIG-I-based therapeutics.
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