Nuclear localization sequences

The end stage of liposomal gene transfer is the entry of the DNA complex into the nucleus of the cell to allow gene transcription (134,135), and entry to the nucleus can by attained following the breakdown of the nuclear envelope 

Inclusion of an NLS consensus peptide into a lipoplex renders nondividing cells susceptible to gene transfection. There is dramatic improvement 

In common with the polylysine DNA-condensing peptide, the p peptide has also been shown to have nuclear localization properties. Confocal microscopy revealed that p peptide in a complex containing fluorescent lipid- and dye-labelled DNA associates with the nuclei and nucleoli of both dividing and nondividing cells within 15 minutes of exposure to the complex, thus suggesting an NLS function. However, this property was not detectable when the peptide became incorporated into a 3p-[N-(N, N -dimethylaminoethane)-carbamoyl]-cholesterol (DC-chol)/DOPE cationic liposome (149). It may be the case that the lipids may mask the critical residues. 

Liposomes can be modified in numerous fashions by the addition of peptide sequences. The benefit of this is that the inclusion of the peptide allows the lipoplex to be optimized for its task such as the targeting a specific cell type with a specific receptor ligand sequence or the transfection of nondividing cells, with an NLS. 

Peptides can also help overcome the most significant drawback to using liposome vectors when compared to viral vectors, which is lower transfection efficiency. Additional benefits include promotion of compaction, assisting cellular uptake of the DNA. Even peptides derived from viruses themselves can be used to compensate this deficit (e.g., adenovirus p protein and the HIV TAT). 

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The NHR contains also the conserved Calcineurin docking site, PxlxIT, required for the physical interaction of NEAT and Calcineurin. Dephosphorylation of at least 13 serines residues in the NHR induces a conformational change that exposes the nuclear localization sequences (NLS), allowing the nuclear translocation of NEAT. Rephosphorylation of these residues unmasks the nuclear export sequences that direct transport back to the cytoplasm. Engagement of receptors such as the antigen receptors in T and B cells is coupled to phospholipase C activation and subsequent production of inositol triphosphate. Increased levels of inositol triphosphate lead to the initial release of intracellular stores of calcium. This early increase of calcium induces opening of the plasma membrane calcium-released-activated-calcium (CRAC) channels,... 

Figure 4 Transfer of DNA from cytoplasm into the nucleoplasm. The DNA-containing complex can enter the nucleus by (1) crossing the membrane during mitotic nuclear membrane breakdown (2) diffusion through nuclear pore for small particles and (3) targeted uptake through the nuclear pore, facilitated by a nuclear localization sequence. Abbreviations NLS, nuclear localization sequence IMP, importin.

The receptors for lipophilic signaling substances all belong to one protein superfamily. They are constructed in a modular fashion from domains with various lengths and functions. Starting from the N terminal, these are the regulatory domain, the DNA-binding domain, a nuclear localization sequence (see p. 228), and the hormone-binding domain (see p. 73D). 

In mammalian cells the El ubiquitin-activating enzyme exists in two isoforms, Ela (110 kDa) and Elb (117 kDa), which are derived from a single gene and mRNA (Cook and Chock 1992, Handley Gearhart et al. 1994). The isoform Ela is predominantly found in the nucleus and has been shown to harbor a functional nuclear localization sequence (NLS) required for nuclear targeting and phosphorylation. In contrast, Elb lacks the NLS, is not phos-phorylated and localized in the cytoplasm (Handley-Gearhart et al. 1994 Stephen et al. 1997). Phosphorylation of Ela was demonstrated to occur in a cell cycle-dependent manner, being maximal in G2 phase (Stephen et al. 

Proteins which act in the nucleus require specific sequences, known as nuclear localization sequences, to direct their transport from the cytoplasm to the nucleus. The nuclear localization sequences are generally found at the C-terminus of a protein and often comprise basic amino acids. 

Phosphorylation in the nuclear localization sequence of transcriptional activators can decide whether transport into the nucleus, and subsequent transcription activation, occms or not. 

In most multicellular eukaryotes, the nuclear envelope breaks down at each cell division, and once division is completed and the nuclear envelope reestablished, the dispersed nuclear proteins must be reimported. To allow this repeated nuclear importation, the signal sequence that targets a protein to the nucleus—the nuclear localization sequence, NLS—is not removed after the protein arrives at its destination. An NLS, unlike other signal sequences, may be located almost anywhere along the primary sequence of the protein. NLSs can vary considerably, but many consist of four to eight amino acid residues and include several consecutive basic (Arg or Lys) residues. 

Chan, C.K. and Jans, D.A. (1999) Enhancement of polylysine-mediated transferrinfection by nuclear localization sequences poly lysine does not function as a nuclear localization sequence. Hum. Gene Ther., 10, 1695-1702. 

Collas, P., Husebye, H. and Alestrom, P. (1996) The nuclear localization sequence of the SV40 T antigen promotes transgene uptake and expression in zebrafish embryo nuclei. Transgenic Res., 5, 451—458. 

After penetrating into cells, these autoantibodies may localize within the cytoplasm or the nucleus, or recycle back to the cell membrane (R6). How do the antibodies localize to the nucleus Conformational analysis of the antibodies indicates that their antigen-binding regions share a tertiary structure resembling nuclear localization sequences (F6). 

NHA NHS NHSCnSH NIL NIR NLO NLS carbon nanohorn aggregate V- h ycl to x v su cc i n i m i de / yl 11 -mercaptoundecanoyl-A-hydroxysuccinimide ester nanoimprint lithography near infrared nonlinear optics nuclear localization sequence (peptide sequence for nuclear targeting)... 

SHIEH, M. W., WESSLER, S. R., RAIKHEL, N. V., Nuclear targeting of the maize R protein requires two nuclear localization sequences, Plant Physiol, 1993, 101,353-361. 

Lin, Y. Z., Yao, S. Y., Veach, R. A., Torgerson, T. R., and Hawiger, J. (1995) Inhibition of nuclear translocation of transcription factor NF-kappa B by a synthetic peptide containing a cell membrane-permeable motif and nuclear localization sequence. J. Biol. Chem. 270, 14,255-14,258. 

NPC, but anything larger must have specific signals, such as nuclear localization sequences to facilitate transport [119],... 

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