scholarly journals Structural and Functional Analysis of the RNA Transport Element, a Member of an Extensive Family Present in the Mouse Genome

2005 ◽  
Vol 79 (4) ◽  
pp. 2356-2365 ◽  
Author(s):  
Sergey Smulevitch ◽  
Daniel Michalowski ◽  
Andrei S. Zolotukhin ◽  
Ralf Schneider ◽  
Jenifer Bear ◽  
...  
Keyword(s):  
Secondary Structure ◽  
Nuclear Export ◽  
Mammalian Cells ◽  
Minimal Element ◽  
Structural Features ◽  
Rna Transport ◽  
Immunodeficiency Virus ◽  
Responsive Element ◽  
Nuclear Export Receptor ◽  
Intracisternal A Particle

ABSTRACT We previously identified an RNA transport element (RTE), present in a subclass of rodent intracisternal A particle retroelements (F. Nappi, R. Schneider, A. Zolotukhin, S. Smulevitch, D. Michalowski, J. Bear, B. Felber, and G. Pavlakis, J. Virol. 75:4558-4569, 2001), that is able to replace Rev-responsive element regulation in human immunodeficiency virus type 1. RTE-directed mRNA export is mediated by a still-unknown cellular factor(s), is independent of the CRM1 nuclear export receptor, and is conserved among vertebrates. Here we show that this RTE folds into an extended RNA secondary structure and thus does not resemble any known RTEs. Computer searches revealed the presence of 105 identical elements and more than 3,000 related elements which share at least 70% sequence identity with the RTE and which are found on all mouse chromosomes. These related elements are predicted to fold into RTE-like structures. Comparison of the sequences and structures revealed that the RTE and related elements can be divided into four groups. Mutagenesis of the RTE revealed that the minimal element contains four internal stem-loops, which are indispensable for function in mammalian cells. In contrast, only part of the element is essential to mediate RNA transport in microinjected Xenopus laevis oocyte nuclei. Importantly, the minimal RTE able to promote RNA transport has key structural features which are preserved in all the RTE-related elements, further supporting their functional importance. Therefore, RTE function depends on a complex secondary structure that is important for the interaction with the cellular export factor(s).

scholarly journals Concerted Action of Multiple cis-Acting Sequences Is Required for Rev Dependence of Late Human Immunodeficiency Virus Type 1 Gene Expression

2000 ◽  
Vol 74 (22) ◽  
pp. 10822-10826 ◽  
Author(s):  
Marcus Graf ◽  
Alexandra Bojak ◽  
Ludwig Deml ◽  
Kurt Bieler ◽  
Hans Wolf ◽  
...  
Keyword(s):  
Human Immunodeficiency Virus ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Nuclear Export ◽  
Regulatory Elements ◽  
Cis Acting ◽  
Immunodeficiency Virus ◽  
Responsive Element ◽  
Hiv 1

ABSTRACT Based on the human immunodeficiency virus type 1 (HIV-1)gag gene, subgenomic reporter constructs have been established allowing the contributions of differentcis-acting elements to the Rev dependency of late HIV-1 gene products to be determined. Modification of intragenic regulatory elements achieved by adapting the codon usage of the complete gene to highly expressed mammalian genes resulted in constitutive nuclear export allowing high levels of Gag expression independent from the Rev/Rev-responsive element system and irrespective of the absence or presence of the isolated major splice donor. Leptomycin B inhibitor studies revealed that the RNAs derived from the codon-optimizedgag gene lacking AU-rich inhibitory elements are directed to a distinct, CRM1-independent, nuclear export pathway.

scholarly journals Cytoplasmic Sequestration of Rel Proteins by IκBα Requires CRM1-Dependent Nuclear Export

2000 ◽  
Vol 20 (6) ◽  
pp. 2269-2284 ◽  
Author(s):  
Winnie F. Tam ◽  
Linda H. Lee ◽  
Laura Davis ◽  
Ranjan Sen
Keyword(s):  
Nuclear Export ◽  
Mammalian Cells ◽  
Regulatory Function ◽  
Main Function ◽  
Cell Cytoplasm ◽  
Leptomycin B ◽  
Major Site ◽  
Cos Cells ◽  
Nuclear Export Receptor ◽  
Nuclear Relocation

ABSTRACT Rel and IκB protein families form a complex cellular regulatory network. A major regulatory function of IκB proteins is to retain Rel proteins in the cell cytoplasm. In addition, IκB proteins have also been postulated to serve nuclear functions. These include the maintenance of inducible NF-κB-dependent gene transcription, as well as termination of inducible transcription. We show that IκBα shuttles between the nucleus and the cytoplasm, utilizing the nuclear export receptor CRM1. A CRM1-binding export sequence was identified in the N-terminal domain of IκBα but not in that of IκBβ or IκBɛ. By reconstituting major aspects of NF-κB–IκB sequestration in yeast, we demonstrate that cytoplasmic retention of p65 (also called RelA) by IκBα requires Crm1p-dependent nuclear export. In mammalian cells, inhibition of CRM1 by leptomycin B resulted in nuclear localization of cotransfected p65 and IκBα in COS cells and enhanced nuclear relocation of endogenous p65 in T cells. These observations suggest that the main function of IκBα is that of a nuclear export chaperone rather than a cytoplasmic tether. We propose that the nucleus is the major site of p65-IκBα association, from where these complexes must be exported in order to create the cytoplasmic pool.

scholarly journals Mutation of the Rev-binding loop in the human immunodeficiency virus 1 leader causes a replication defect characterized by altered RNA trafficking and packaging

2006 ◽  
Vol 87 (10) ◽  
pp. 3039-3044 ◽  
Author(s):  
Jane S. Greatorex ◽  
Elizabeth A. Palmer ◽  
Roger J. Pomerantz ◽  
John A. Dangerfield ◽  
Andrew M. L. Lever
Keyword(s):  
Human Immunodeficiency Virus ◽  
Nuclear Export ◽  
Rna Packaging ◽  
Packaging Signal ◽  
Virus Particles ◽  
Immunodeficiency Virus ◽  
Responsive Element ◽  
Viral Genomic Rna ◽  
Human Immunodeficiency Virus 1

An internal RNA loop, located within the packaging signal of human immunodeficiency virus 1, that resembles the Rev-responsive element (RRE) closely was identified previously. Subsequent in vitro studies confirmed that the loop, termed loop A, could bind Rev protein specifically. Its proximity to the major splice donor has suggested a role for Rev–loop A interaction supplementary to or preceding that of the Rev–RRE interaction. To investigate this further in a replication-competent provirus, loop A was mutated to decrease its affinity for Rev. Impairing the Rev–loop A interaction led to reduced nuclear export of viral genomic RNA. RNA packaging decreased by approximately 30 %. Viral protein production and export of virus particles appeared normal; however, the virus was severely replication-deficient. The loop A sequence, which is 98 % conserved amongst viral isolates, is implicated in several cis-acting functions critical to virus viability.

scholarly journals Phenotypic analysis of human immunodeficiency virus type 1 Rev trimerization-interface mutants in human cells

2005 ◽  
Vol 86 (5) ◽  
pp. 1509-1513 ◽  
Author(s):  
Roochi Trikha ◽  
David W. Brighty
Keyword(s):  
Human Immunodeficiency Virus ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Nuclear Export ◽  
Mammalian Cells ◽  
Dominant Negative ◽  
Phenotypic Analysis ◽  
Rev Response Element ◽  
Immunodeficiency Virus

Nuclear export of unspliced and incompletely spliced human immunodeficiency virus type 1 mRNA is mediated by the viral Rev protein. Rev binds to a structured RNA motif known as the Rev-response element (RRE), which is present in all Rev-dependent transcripts, and thereby promotes entry of the ribonucleoprotein complex into the nuclear-export pathway. Recent evidence indicates that a dimerization interface and a genetically separable ‘trimerization’ interface are required for multimeric assembly of Rev on the RRE. In this report, the effect of mutations within the trimerization interface on Rev function was examined in mammalian cells. All trimerization-defective Rev molecules had profoundly compromised Rev function and a range of localization defects was observed. However, despite the potential for formation of heterodimers between functional and non-functional Rev proteins, trimerization-defective Rev mutants were unable to inhibit wild-type Rev function in a trans-dominant-negative manner.

Nuclear pore localization and nucleocytoplasmic transport of eIF-5A: evidence for direct interaction with the export receptor CRM1

1999 ◽  
Vol 112 (14) ◽  
pp. 2369-2380 ◽  
Author(s):  
O. Rosorius ◽  
B. Reichart ◽  
F. Kratzer ◽  
P. Heger ◽  
M.C. Dabauvalle ◽  
...  
Keyword(s):  
Nuclear Export ◽  
Mammalian Cells ◽  
Direct Interaction ◽  
Nucleocytoplasmic Transport ◽  
Cellular Protein ◽  
Initiation Factor ◽  
Immunogold Electron Microscopy ◽  
Nuclear Pore ◽  
Nuclear Export Receptor

Eukaryotic initiation factor 5A (eIF-5A) is the only cellular protein known to contain the unusual amino acid hypusine. The exact in vivo function of eIF-5A, however, is to date unknown. The finding that eIF-5A is an essential cofactor of the human immunodeficiency virus type 1 (HIV-1) Rev RNA transport factor suggested that eIF-5A is part of a specific nuclear export pathway. In this study we used indirect immunofluorescence and immunogold electron microscopy to demonstrate that eIF-5A accumulates at nuclear pore-associated intranuclear filaments in mammalian cells and Xenopus oocytes. We are able to show that eIF-5A interacts with the general nuclear export receptor, CRM1. Furthermore, microinjection studies in somatic cells revealed that eIF-5A is transported from the nucleus to the cytoplasm, and that this nuclear export is blocked by leptomycin B. Our data demonstrate that eIF-5A is a nucleocytoplasmic shuttle protein.

scholarly journals A structured retroviral RNA element that mediates nucleocytoplasmic export of intron-containing RNA.

1997 ◽  
Vol 17 (1) ◽  
pp. 135-144 ◽  
Author(s):  
R K Ernst ◽  
M Bray ◽  
D Rekosh ◽  
M L Hammarskjöld
Keyword(s):  
Nuclear Export ◽  
Nuclear Export Signal ◽  
Regulatory Proteins ◽  
Cellular Factors ◽  
Immunodeficiency Virus ◽  
Rna Export ◽  
Viral Regulatory Proteins ◽  
Responsive Element ◽  
Nucleocytoplasmic Export ◽  
Hiv 1

A common feature of gene expression in all retroviruses is that unspliced, intron-containing RNA is exported to the cytoplasm despite the fact that cellular RNAs which contain introns are usually restricted to the nucleus. In complex retroviruses, the export of intron-containing RNA is mediated by specific viral regulatory proteins (e.g., human immunodeficiency virus type 1 [HIV-1] Rev) that bind to elements in the viral RNA. However, simpler retroviruses do not encode such regulatory proteins. Here we show that the genome of the simpler retrovirus Mason-Pfizer monkey virus (MPMV) contains an element that serves as an autonomous nuclear export signal for intron-containing RNA. This element is essential for MPMV replication; however, its function can be complemented by HIV-1 Rev and the Rev-responsive element. The element can also facilitate the export of cellular intron-containing RNA. These results suggest that the MPMV element mimics cellular RNA transport signals and mediates RNA export through interaction with endogenous cellular factors.

scholarly journals Involvement of CRM1, a nuclear export receptor, in mRNA export in mammalian cells and fission yeast

1999 ◽  
Vol 4 (5) ◽  
pp. 291-297 ◽  
Author(s):  
Mina Watanabe ◽  
Makoto Fukuda ◽  
Minoru Yoshida ◽  
Mitsuhiro Yanagida ◽  
Eisuke Nishida
Keyword(s):  
Fission Yeast ◽  
Nuclear Export ◽  
Mammalian Cells ◽  
Mrna Export ◽  
Nuclear Export Receptor
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