scholarly journals Nuclear Import Receptors and hnRNP K Mediates Nuclear and Stress Granule Localization of SIRLOIN

2021 ◽  
Author(s):  
Jialin Yao ◽  
Qiao Zhou ◽  
Hengyi Xiao ◽  
Da Jia ◽  
Qingxiang Sun
Keyword(s):  
Nuclear Import ◽  
Rna Binding ◽  
Weak Interactions ◽  
Underlying Mechanism ◽  
Stress Granule ◽  
Hnrnp K ◽  
Permeabilized Cells ◽  
Import Receptors ◽  
Rna Motif ◽  
Import Receptor

Abstract The majority of lncRNAs and a small fraction of mRNAs localize in the cell nucleus to exert their functions. A SIRLOIN RNA motif was previously reported to drive its nuclear localization by the RNA-binding protein hnRNP K. However, the underlying mechanism remains unclear. Here, we report crystal structures of hnRNP K in complex with SIRLOIN, and with the nuclear import receptor (NIR) Impα1, respectively. The protein hnRNP K bound to SIRLOIN with multiple weak interactions, and interacted Impα1 using an independent high-affinity site. Forming a complex with hnRNP K and Impα1 was essential for the nuclear and stress granule localization of SIRLOIN in semi-permeabilized cells. Nuclear import of SIRLOIN enhanced with increasing NIR concentrations, but its stress granule localization peaked at a low NIR concentration. Collectively, we propose a mechanism of SIRLOIN localization, in which NIRs functioned as drivers/regulators, and hnRNP K as an adaptor.

scholarly journals Nonclassical nuclear localization signals mediate nuclear import of CIRBP

2020 ◽  
Vol 117 (15) ◽  
pp. 8503-8514 ◽  
Author(s):  
Benjamin Bourgeois ◽  
Saskia Hutten ◽  
Benjamin Gottschalk ◽  
Mario Hofweber ◽  
Gesa Richter ◽  
...  
Keyword(s):  
Phase Separation ◽  
Nuclear Localization ◽  
Nuclear Import ◽  
Rna Binding ◽  
Rna Binding Proteins ◽  
Specific Interaction ◽  
Stress Granule ◽  
Rich Region ◽  
Nuclear Localization Signals ◽  
Cargo Proteins

The specific interaction of importins with nuclear localization signals (NLSs) of cargo proteins not only mediates nuclear import but also, prevents their aberrant phase separation and stress granule recruitment in the cytoplasm. The importin Transportin-1 (TNPO1) plays a key role in the (patho-)physiology of both processes. Here, we report that both TNPO1 and Transportin-3 (TNPO3) recognize two nonclassical NLSs within the cold-inducible RNA-binding protein (CIRBP). Our biophysical investigations show that TNPO1 recognizes an arginine-glycine(-glycine) (RG/RGG)–rich region, whereas TNPO3 recognizes a region rich in arginine-serine-tyrosine (RSY) residues. These interactions regulate nuclear localization, phase separation, and stress granule recruitment of CIRBP in cells. The presence of both RG/RGG and RSY regions in numerous other RNA-binding proteins suggests that the interaction of TNPO1 and TNPO3 with these nonclassical NLSs may regulate the formation of membraneless organelles and subcellular localization of numerous proteins.

scholarly journals Adenovirus Core Protein pVII Is Translocated into the Nucleus by Multiple Import Receptor Pathways

2006 ◽  
Vol 80 (19) ◽  
pp. 9608-9618 ◽  
Author(s):  
Harald Wodrich ◽  
Aurelia Cassany ◽  
Maximiliano A. D'Angelo ◽  
Tinglu Guan ◽  
Glen Nemerow ◽  
...  
Keyword(s):  
Recombinant Protein ◽  
Nuclear Import ◽  
Cultured Cells ◽  
Core Protein ◽  
Deletion Mapping ◽  
Nuclear Entry ◽  
Permeabilized Cells ◽  
Importin Α ◽  
Import Receptors

ABSTRACT Adenoviruses are nonenveloped viruses with an ∼36-kb double-stranded DNA genome that replicate in the nucleus. Protein VII, an abundant structural component of the adenovirus core that is strongly associated with adenovirus DNA, is imported into the nucleus contemporaneously with the adenovirus genome shortly after virus infection and may promote DNA import. In this study, we evaluated whether protein VII uses specific receptor-mediated mechanisms for import into the nucleus. We found that it contains potent nuclear localization signal (NLS) activity by transfection of cultured cells with protein VII fusion constructs and by microinjection of cells with recombinant protein VII fusions. We identified three NLS-containing regions in protein VII by deletion mapping and determined important NLS residues by site-specific mutagenesis. We found that recombinant protein VII and its NLS-containing domains strongly and specifically bind to importin α, importin β, importin 7, and transportin, which are among the most abundant cellular nuclear import receptors. Moreover, these receptors can mediate the nuclear import of protein VII fusions in vitro in permeabilized cells. Considered together, these data support the hypothesis that protein VII is a major NLS-containing adaptor for receptor-mediated import of adenovirus DNA and that multiple import pathways are utilized to promote efficient nuclear entry of the viral genome.

scholarly journals Nuclear Import of c-Jun Is Mediated by Multiple Transport Receptors

2007 ◽  
Vol 282 (38) ◽  
pp. 27685-27692 ◽  
Author(s):  
Inga Waldmann ◽  
Sarah Wälde ◽  
Ralph H. Kehlenbach
Keyword(s):  
Transcription Factor ◽  
Nuclear Import ◽  
Leucine Zipper ◽  
Dependent Manner ◽  
Reporter Protein ◽  
Permeabilized Cells ◽  
Import Receptors ◽  
Factor C

c-Jun and c-Fos are major components of the transcriptional complex AP-1. Here, we investigate the nuclear import pathway(s) of the transcription factor c-Jun. c-Jun bound specifically to the nuclear import receptors importin β, transportin, importin 5, importin 7, importin 9, and importin 13. In digitonin-permeabilized cells, importin β, transportin, importin 7, and importin 9 promoted efficient import of c-Jun into the nucleus. Importin α, by contrast, inhibited nuclear import of c-Jun in vitro. A single basic region preceding the leucine zipper of c-Jun functions as a nuclear localization signal (NLS) and was required for interaction with all tested import receptors. In vivo, nuclear import of a c-Jun reporter protein lacking the leucine zipper strictly depended on this NLS. In a leucine zipper-dependent manner, c-Jun with mutations in its NLS was still imported into the nucleus in a complex with endogenous leucine zipper proteins or, for example, with cotransfected c-Fos. Together, these results explain the highly efficient nuclear import of the transcription factor c-Jun.

scholarly journals Early retinal neurodegeneration and impaired Ran-mediated nuclear import of TDP-43 in progranulin-deficient FTLD

2014 ◽  
Vol 211 (10) ◽  
pp. 1937-1945 ◽  
Author(s):  
Michael E. Ward ◽  
Alice Taubes ◽  
Robert Chen ◽  
Bruce L. Miller ◽  
Chantelle F. Sephton ◽  
...  
Keyword(s):  
Nuclear Import ◽  
Rna Binding ◽  
Underlying Mechanism ◽  
Small Gtpase ◽  
Retinal Neuron ◽  
Gene Encoding ◽  
Retinal Neurodegeneration ◽  
Retinal Thinning ◽  
Gtpase Ran ◽  
Dementia Onset

Frontotemporal dementia (FTD) is the most common cause of dementia in people under 60 yr of age and is pathologically associated with mislocalization of TAR DNA/RNA binding protein 43 (TDP-43) in approximately half of cases (FLTD-TDP). Mutations in the gene encoding progranulin (GRN), which lead to reduced progranulin levels, are a significant cause of familial FTLD-TDP. Grn-KO mice were developed as an FTLD model, but lack cortical TDP-43 mislocalization and neurodegeneration. Here, we report retinal thinning as an early disease phenotype in humans with GRN mutations that precedes dementia onset and an age-dependent retinal neurodegenerative phenotype in Grn-KO mice. Retinal neuron loss in Grn-KO mice is preceded by nuclear depletion of TDP-43 and accompanied by reduced expression of the small GTPase Ran, which is a master regulator of nuclear import required for nuclear localization of TDP-43. In addition, TDP-43 regulates Ran expression, likely via binding to its 3′-UTR. Augmented expression of Ran in progranulin-deficient neurons restores nuclear TDP-43 levels and improves their survival. Our findings establish retinal neurodegeneration as a new phenotype in progranulin-deficient FTLD, and suggest a pathological loop involving reciprocal loss of Ran and nuclear TDP-43 as an underlying mechanism.

scholarly journals Transportin-SR, a Nuclear Import Receptor for SR Proteins

1999 ◽  
Vol 145 (6) ◽  
pp. 1145-1152 ◽  
Author(s):  
Naoyuki Kataoka ◽  
Jennifer L. Bachorik ◽  
Gideon Dreyfuss
Keyword(s):  
Nuclear Import ◽  
Protein Import ◽  
Sequence Similarity ◽  
Sr Proteins ◽  
Amino Acid Sequence Similarity ◽  
Sr Protein ◽  
Localization Signal ◽  
Import Receptors ◽  
Import Receptor

The SR proteins, a group of abundant arginine/serine (RS)-rich proteins, are essential pre-mRNA splicing factors that are localized in the nucleus. The RS domain of these proteins serves as a nuclear localization signal. We found that RS domain–bearing proteins do not utilize any of the known nuclear import receptors and identified a novel nuclear import receptor specific for SR proteins. The SR protein import receptor, termed transportin-SR (TRN-SR), binds specifically and directly to the RS domains of ASF/SF2 and SC35 as well as several other SR proteins. The nuclear transport regulator RanGTP abolishes this interaction. Recombinant TRN-SR mediates nuclear import of RS domain– bearing proteins in vitro. TRN-SR has amino acid sequence similarity to several members of the importin β/transportin family. These findings strongly suggest that TRN-SR is a nuclear import receptor for the SR protein family.

scholarly journals Importin 7 and Importin α/Importin β Are Nuclear Import Receptors for the Glucocorticoid Receptor

2004 ◽  
Vol 15 (5) ◽  
pp. 2276-2286 ◽  
Author(s):  
Neal D. Freedman ◽  
Keith R. Yamamoto
Keyword(s):  
Glucocorticoid Receptor ◽  
Nuclear Import ◽  
Hormonal Control ◽  
Nuclear Localization Signals ◽  
Cell Extracts ◽  
Importin Α ◽  
Import Receptors ◽  
Unidentified Component ◽  
Import Receptor

The vertebrate glucocorticoid receptor (GR) is cytoplasmic without hormone and localizes to the nucleus after hormone binding. GR has two nuclear localization signals (NLS): NL1 is similar in sequence to the SV40 NLS; NL2 is poorly defined, residing in the ligand-binding domain. We found that GR displayed similar hormone-regulated compartmentalization in Saccharomyces cerevisiae and required the Sxm1 nuclear import receptor for NL2-mediated import. Two metazoan homologues of Sxm1, importin 7 and importin 8, bound both NL1 and NL2, whereas importin α selectively bound NL1. In an in vitro nuclear import assay, both importin 7 and the importin α-importin β heterodimer could import a GR NL1 fragment. Under these conditions, full-length GR localized to nuclei in the presence but not absence of an unidentified component in cell extracts. Interestingly, importin 7, importin 8, and importin α bound GR even in the absence of hormone; thus, hormonal control of localization is exerted at a step downstream of import receptor binding.

Arabidopsis transportin1 is the nuclear import receptor for the circadian clock-regulated RNA-binding protein AtGRP7

2003 ◽  
Vol 53 (1/2) ◽  
pp. 201-212 ◽  
Author(s):  
Alicja Ziemienowicz ◽  
Dorothea Haasen ◽  
Dorothee Staiger ◽  
Thomas Merkle
Keyword(s):  
Circadian Clock ◽  
Nuclear Import ◽  
Rna Binding ◽  
Binding Protein ◽  
Rna Binding Protein ◽  
Import Receptor

scholarly journals The L2 Minor Capsid Protein of Human Papillomavirus Type 16 Interacts with a Network of Nuclear Import Receptors

2004 ◽  
Vol 78 (22) ◽  
pp. 12179-12188 ◽  
Author(s):  
Medha S. Darshan ◽  
John Lucchi ◽  
Emily Harding ◽  
Junona Moroianu
Keyword(s):  
Human Papillomavirus ◽  
Nuclear Import ◽  
Capsid Proteins ◽  
Permeabilized Cells ◽  
Nuclear Localization Signals ◽  
Human Papillomavirus Type 16 ◽  
C Terminus ◽  
Binding Data ◽  
Import Receptors ◽  
Productive Phase

ABSTRACT The L2 minor capsid proteins enter the nucleus twice during viral infection: in the initial phase after virion disassembly and in the productive phase when, together with the L1 major capsid proteins, they assemble the replicated viral DNA into virions. In this study we investigated the interactions between the L2 protein of high-risk human papillomavirus type 16 (HPV16) and nuclear import receptors. We discovered that HPV16 L2 interacts directly with both Kapβ2 and Kapβ3. Moreover, binding of Ran-GTP to either Kapβ2 or Kapβ3 inhibits its interaction with L2, suggesting that the Kapβ/L2 complex is import competent. In addition, we found that L2 forms a complex with the Kapα2β1 heterodimer via interaction with the Kapα2 adapter. In agreement with the binding data, nuclear import of L2 in digitonin-permeabilized cells could be mediated by either Kapα2β1 heterodimers, Kapβ2, or Kapβ3. Mapping studies revealed that HPV16 L2 contains two nuclear localization signals (NLSs), in the N terminus (nNLS) and C terminus (cNLS), that could mediate its nuclear import. Together the data suggest that HPV16 L2 interacts via its NLSs with a network of karyopherins and can enter the nucleus via several import pathways mediated by Kapα2β1 heterodimers, Kapβ2, and Kapβ3.

scholarly journals Defective nuclear import of Tpr in Progeria reflects the Ran sensitivity of large cargo transport

2013 ◽  
Vol 201 (4) ◽  
pp. 541-557 ◽  
Author(s):  
Chelsi J. Snow ◽  
Ashraf Dar ◽  
Anindya Dutta ◽  
Ralph H. Kehlenbach ◽  
Bryce M. Paschal
Keyword(s):  
Nuclear Import ◽  
Protein Complexes ◽  
Nucleocytoplasmic Transport ◽  
Large Protein ◽  
Localization Signal ◽  
Import Receptors ◽  
Progeria Syndrome ◽  
Hutchinson Gilford Progeria Syndrome ◽  
Major Defect ◽  
Import Receptor

The RanGTPase acts as a master regulator of nucleocytoplasmic transport by controlling assembly and disassembly of nuclear transport complexes. RanGTP is required in the nucleus to release nuclear localization signal (NLS)–containing cargo from import receptors, and, under steady-state conditions, Ran is highly concentrated in the nucleus. We previously showed the nuclear/cytoplasmic Ran distribution is disrupted in Hutchinson-Gilford Progeria syndrome (HGPS) fibroblasts that express the Progerin form of lamin A, causing a major defect in nuclear import of the protein, translocated promoter region (Tpr). In this paper, we show that Tpr import was mediated by the most abundant import receptor, KPNA2, which binds the bipartite NLS in Tpr with nanomolar affinity. Analyses including NLS swapping revealed Progerin did not cause global inhibition of nuclear import. Rather, Progerin inhibited Tpr import because transport of large protein cargoes was sensitive to changes in the Ran nuclear/cytoplasmic distribution that occurred in HGPS. We propose that defective import of large protein complexes with important roles in nuclear function may contribute to disease-associated phenotypes in Progeria.

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