Nuclear pore complex electron microscopy

Akey, C.W. and Radermacher, M. (1993) Architecture of the Xenopus nuclear pore complex revealed by three-dimensional cry o-electron microscopy. J. Cell Biol., 122, 1-19. 

Nuclear entry has been described as a formidable barrier to gene delivery [201-203]. Transport of DNA into this target organelle most likely involves the nuclear pore complex, which has an inner channel size of 9 nm, as determined by electron microscopy [204]. Molecules less than 40-45 kDa diffuse freely through the... 

An illustrative example of combining protein modeling and electron microscopy data is the case of the apoptosome, an Apaf-1 cytochrome c complex that activates procaspase-9 [40]. The data obtained in this work helped to decipher the exact mechanism of a very important apoptosis triggering mechanism. Another interesting example is the use of computational and biochemical methods to conduct structural analyses of the seven proteins that compose the core building block of the nuclear pore complex [41]. 

A FIGURE 12-18 Nuclear pore complex, (a) Nuclear envelopes microdissected from the large nuclei of Xenopus oocytes visualized by field emission in-lens scanning electron microscopy. Top View of the cytoplasmic face reveals octagonal shape of membrane-embedded portion of nuclear pore complexes. Bottom V ew of the nucleoplasmic face shows the nuclear basket that extends from the membrane portion, (b) Cut-away model of the pore complex. [Part (a) from V Doye and E. Elurt, 1997 Curr. Opin. Cell Biol. 9 401 courtesy of M. W. Goldberg and I D. Allen. Part (b) adapted from M. R Rout and J. D. Atchison, 2001, J. Biol. Chem. 276 16593.]... 

Another participant in mRNP transport to the cytoplasm Is the nuclear cap-bIndIng complex, mentioned earlier as protection against exonuclease attack on the 5 end of nascent transcripts and pre-mRNAs. Electron microscopy experiments discussed below have demonstrated that the 5 end of mRNAs lead the way through the nuclear pore complex. Recent experiments in yeast indicate that the 3 poly(A) tail plays an Important role In mRNP transport, suggesting that a poly(A)-binding protein participates. Nucleoporins associated with the NPC cytoplasmic filaments In addition to FG-nucleoporins are required for mRNA export and may function to dissociate the mRNA-exporter and other mRNP proteins that accompany the mRNP through the pore. 

Ris, H. (1991). The three-dimensional structure of the nuclear pore complex as seen by high voltage electron microscopy and high resolution low voltage scanning electron microscopy. EMSA Bull. 21, 54-56. 

Mapping Proteins to Nuclear Pore Complexes by Immunogold Electron Microscopy... 

Goldberg, M. W., and Allen, T. D. (1966). The nuclear pore complex and lamina Three-dimensional structures and interactions determined by field emission in-lens scanning electron microscopy. J. Mol Biol 257, 848-865. 

Grote, M., Kubitscheck, U., Reichelt, R., and Peters, R. (1995). Mapping of nucleoporins to the center of the nuclear pore complex by post-embedding immunogold electron microscopy. J. Cell Scl 108, 2963-2972. 

Reassembly of nuclei can be followed most easily by phase-contrast microscopy. During the course of the assembly reaction clusters of chromosomes will be observed to fuse into single masses of chromatin, which will eventually become spherical in shape as decondensation progresses. At this point, thin-section electron microscopy should reveal the presence of a continuous double membrane studded with nuclear pore complexes surrounding each chromatin mass. Assembly of individual nuclear envelope components such as nuclear lamins or nuclear pore complex proteins can best be analyzed by immunofluorescence microscopy (Burke and Gerace, 1986). This is performed as follows. 

Figure 10 Components of the nuclear pore complex. Structures are available from the PDB and EMDB for some of the components of the nuclear core complex. The individual proteins and small subassemblies shown in ribbon representation are from six PDB entries that provide atomic-level information from X-ray (4GQ2, 3UKY, 4FHN, 3TKN, 4GQ1) or nuclear magnetic resonance spectroscopy (2EC1) studies. The three larger subassemblies drawn as surfaces have been analyzed by cryo-electron microscopy (EMD-5152, EMD-1097) or cryo-electron tomography (EMD-1394).

Annulate lamellae (Fig. 229) are intracytoplasmic membrane systems composed of parallel arrays of cisternae bearing at regular intervals small annuli or fenestrae. As shown by electron microscopy, the structure of the aimulate lamellae pore complex is similar to that of the pore complexes of the nuclear envelope. When melatonin was administered to rats or when rats were kept in darkness Freire and Cardinali (1975) observed changes in the ultra-... 

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