Nuclear Transport (nuclear + transport)

Distribution by Scientific Domains


Selected Abstracts


Heterodimerization with LBP-1b is necessary for nuclear localization of LBP-1a and LBP-1c

GENES TO CELLS, Issue 9 2005
Fuyuhiko Sato
The LBP-1 family consists of four proteins, which act as transcription factors in the formation of dimers with a member of this family. LBP-1a and LBP-1b are splicing variants from one gene, and LBP-1c and LBP-1d also arise from the alternative splicing of another gene. Investigation of subcellular localization of LBP-1 proteins fused to YFP revealed that the LBP-1b was localized in the nucleus, whereas LBP-1a and LBP-1c were exclusively localized in the cytosol. The peptide of 36 amino acids encoded by exon 6, a specific exon used only for LBP-1b, possessed the function of a nuclear localization signal (NLS). Nuclear localization of LBP-1a and LBP-1c occurred when LBP-1b was co-expressed, suggesting that heterodimerization of LBP-1a and LBP-1c with LBP-1b is important for their nuclear transport. Transiently expressed LBP-1 proteins in COS-7 cells formed speckles in the nucleus. Most speckles overlapped with the PML body. The activity of LBP-1a for accumulation in the PML body was mapped in the N-terminal region. [source]


Nucleocytoplasmic protein traffic and its significance to cell function

GENES TO CELLS, Issue 10 2000
Yoshihiro Yoneda
In eukaryotic cells, cell functions are maintained in an orderly manner through the continuous traffic of various proteins between the cell nucleus and the cytoplasm. The nuclear import and export of proteins occurs through nuclear pore complexes and typically requires specific signals: the nuclear localization signal and nuclear export signal, respectively. The transport pathways have been found to be highly divergent, but are known to be largely mediated by importin ,-like transport receptor family molecules. These receptor molecules bind to and carry their cargoes directly or via adapter molecules. A small GTPase Ran ensures the directionality of nuclear transport by regulating the interaction between the receptors and their cargoes through its GTP/GDP cycle. Moreover, it has been recently elucidated how the transport system is involved in various functions of cell physiology, such as cell cycle control. [source]


Nuclear localization signals and human disease

IUBMB LIFE, Issue 7 2009
Laura M. McLane
Abstract In eukaryotic cells, the physical separation of the genetic material in the nucleus from the translation and signaling machinery in the cytoplasm by the nuclear envelope creates a requirement for a mechanism through which macromolecules can enter or exit the nucleus as necessary. Nucleocytoplasmic transport involves the specific recognition of cargo molecules by transport receptors in one compartment followed by the physical relocation of that cargo into the other compartment through regulated pores that perforate the nuclear envelope. The recognition of protein cargoes by their transport receptors occurs via amino acid sequences in cargo proteins called nuclear targeting signals. Both nuclear import and export of proteins are highly regulated processes that control, not only what cargo can enter and/or exit the nucleus, but also when in the cell cycle and in what cell type, the cargo can be transported. Deregulation of the nuclear transport of specific cargoes has been linked to numerous cancers and developmental disorders highlighting the importance of understanding the mechanisms underlying nucleocytoplasmic transport and particularly the modulation of the specific interactions between transporter receptors and nuclear targeting signals within target cargo proteins. © 2009 IUBMB IUBMB Life 61(7): 697,706, 2009 [source]


Role of O -linked ,- N -acetylglucosamine modification in the subcellular distribution of alpha4 phosphoprotein and Sp1 in rat lymphoma cells

JOURNAL OF CELLULAR BIOCHEMISTRY, Issue 3 2005
Shauna M. Dauphinee
Abstract The mTOR alpha4 phosphoprotein is a prolactin (PRL)-downregulated gene product that is found in the nucleus of PRL-dependent rat Nb2 lymphoma cells. Alpha4 lacks a nuclear localization signal (NLS) and the mechanism of its nuclear targeting is unknown. Post-translational modification by O -linked ,- N -acetylglucosamine (O -GlcNAc) moieties has been implicated in the nuclear transport of some proteins, including transcription factor Sp1. The nucleocytoplasmic enzymes O -,- N -acetylglucosaminyltransferase (OGT) and O -,- N -acetylglucosaminidase (O -GlcNAcase) adds or remove O -GlcNAc moieties, respectively. If O -GlcNac moieties contribute to the nuclear targeting of alpha4, a decrease in O -GlcNAcylation (e.g., by inhibition of OGT) may redistribute alpha4 to the cytosol. The present study showed that alpha4 and Sp1 were both O -GlcNAcylated in quiescent and PRL-treated Nb2 cells. PRL alone or PRL,+,streptozotocin (STZ; an O -GlcNAcase inhibitor) significantly (P,,,0.05) increased the O -GlcNAc/alpha4 ratio above that in control quiescent cells. However, PRL,+,alloxan (ALX; an OGT inhibitor) or ALX alone did not decrease O -GlcNAcylation of alpha4 below that of controls and alpha4 remained nuclear. In comparison, PRL (±ALX/STZ) greatly increased Sp1 protein levels, caused a significant decrease in the GlcNAc/Sp1 ratio (P,,,0.05, n,=,3) as compared to controls and partially redistributed Sp1 to the cytosol. Finally, a 50% downregulation of OGT gene expression by small interfering RNA (i.e., siOGT) partially redistributed both alpha4 and Sp1 to the cytosol. The alpha4 protein partner PP2Ac had no detectable O -GlcNAc moieties and its nuclear distribution was not affected by siOGT. In summary, alpha4 and Sp1 contained O -GlcNAc moieties, which contributed to their nuclear targeting in Nb2 cells. © 2005 Wiley-Liss, Inc. [source]