RESUMO
To ensure efficient and accurate gene expression, pre-mRNA processing and mRNA export need to be balanced. However, how this balance is ensured remains largely unclear. Here, we found that SF3b, a component of U2 snRNP that participates in splicing and 3' processing of pre-mRNAs, interacts with the key mRNA export adaptor THO in vivo and in vitro. Depletion of SF3b reduces THO binding with the mRNA and causes nuclear mRNA retention. Consistently, introducing SF3b binding sites into the mRNA enhances THO recruitment and nuclear export in a dose-dependent manner. These data demonstrate a role of SF3b in promoting mRNA export. In support of this role, SF3b binds with mature mRNAs in the cells. Intriguingly, disruption of U2 snRNP by using a U2 antisense morpholino oligonucleotide does not inhibit, but promotes, the role of SF3b in mRNA export as a result of enhanced SF3b-THO interaction and THO recruitment to the mRNA. Together, our study uncovers a U2-snRNP-independent role of SF3b in mRNA export and suggests that SF3b contributes to balancing pre-mRNA processing and mRNA export.
Assuntos
Fosfoproteínas , Precursores de RNA , Fatores de Processamento de RNA , RNA Mensageiro , Ribonucleoproteína Nuclear Pequena U2 , Sítios de Ligação/genética , Células HeLa , Humanos , Proteínas Nucleares/genética , Proteínas Nucleares/metabolismo , Fosfoproteínas/genética , Fosfoproteínas/metabolismo , Precursores de RNA/genética , Precursores de RNA/metabolismo , Splicing de RNA/genética , Fatores de Processamento de RNA/genética , Fatores de Processamento de RNA/metabolismo , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Ribonucleoproteína Nuclear Pequena U2/genética , Ribonucleoproteína Nuclear Pequena U2/metabolismoRESUMO
Human RNase MRP ribonucleoprotein complex is an essential endoribonuclease involved in the processing of ribosomal RNAs, mitochondrial RNAs and certain messenger RNAs. Its RNA subunit RMRP catalyzes the cleavage of substrate RNAs, and the protein components of RNase MRP are required for activity. RMRP mutations are associated with several types of inherited developmental disorders, but the pathogenic mechanism is largely unknown. Recent structural studies shed lights on the catalytic mechanism of yeast RNase MRP and the closely related RNase P; however, the structural and catalytic mechanism of RMRP in human RNase MRP complex remains unclear. Here we report the crystal structure of the P3 domain of RMRP in complex with the RPP20 and RPP25 proteins of human RNase MRP, which shows that the P3 RNA binds to a conserved positively-charged surface of the RPP20-RPP25 heterodimer through its distal stem and internal loop regions. The disease-related mutations of RMRPP3 are mostly located at the protein-RNA interface and are likely to weaken the binding of P3 to RPP20-RPP25. Moreover, the structure reveals a homodimeric organization of the entire RPP20-RPP25-RMRPP3 complex, which might mediate the dimerization of human RNase MRP complex in cells. These findings provide structural clues to the assembly and pathogenesis of human RNase MRP complex and also reveal a tetrameric feature of RPP20-RPP25 evolutionarily conserved with that of the archaeal Alba proteins.
Assuntos
Autoantígenos/química , RNA Longo não Codificante/química , Ribonuclease P/química , Proteínas Arqueais/química , Autoantígenos/metabolismo , Cristalografia por Raios X , Dimerização , Humanos , Modelos Moleculares , Complexos Multiproteicos/química , Complexos Multiproteicos/metabolismo , Conformação de Ácido Nucleico , Conformação Proteica , RNA Longo não Codificante/genética , RNA Longo não Codificante/metabolismo , Ribonuclease P/metabolismoRESUMO
Superhydrophobic surfaces face challenges in comprehensive durability when used in extreme outdoor environments. Here, we present a protocol for preparing nanocomposite bulks with hierarchical structures using the template technique. We describe steps for using hybrid nanoparticles of polytetrafluoroethylene and multi-walled carbon nanotube to fill inside and dip on the polyurethane (PU) foam. We then detail procedures for its removal by sintering treatment. The extra accretion layer on the PU foam surface was highlighted to construct hierarchical porous structures. For complete details on the use and execution of this protocol, please refer to Wu et al.1.
Assuntos
Porosidade , Interações Hidrofóbicas e HidrofílicasRESUMO
There has been little research focus on the interface problems of phthalonitrile (PN) resin and carbon fiber. However, interface performance is related to the overall mechanical properties of composites and is very important. This study focused on the interfacial performance and adhesion mechanism of a carbon fiber Cf/PN composite. Micro-composites of Cf/PN and Cf/epoxy resins were prepared, and their interfacial shear strengths (IFSS) were tested by micro-droplet testing. The result showed that the IFSS of Cf/PN was higher than that of Cf/epoxy resin, indicating that the interfacial adhesion of the PN matrix composite must be more effective. To explain the obtained results, a number of tests, including SEM, SEM-EDS, FTIR, and TGA, were carried out. From the SEM analyses, cured PN polymer films were found on the surface of de-bonded carbon fibers. With the aid of SEM-EDS, the elements on the de-bonded carbon fiber surface of the Cf/PN composite were detected in situ. An interesting synchronous relationship was observed in the IFSS and SEM-EDS results. Through the FTIR spectra, the chemical structures of the PN polymers were identified. From the detailed analyses and discussion in this work, the effective interfacial bond function in the Cf/PN composite appears to be a complex result for all relative functions. The functional advantage of the PN composite may be the interface conjugation between the PN polymers and the graphene layer on the surface of the carbon fiber.