Mtr10p functions as a nuclear import receptor for the mRNA-binding protein Npl3p

Senger, Bruno; Simos, George; Bischoff, F. Ralf; Podtelejnikov, Alexandre V.; Mann, Matthias; Hurt, Ed

doi:10.1093/emboj/17.8.2196

Cited by 178 publications

(195 citation statements)

References 62 publications

Supporting

Mentioning

179

Contrasting

Order By: Relevance

“…Mtr10 has been reported to be essential (17); however, we and others (32,33) find that strains lacking MTR10 grow slowly. Interestingly, Mtr10 has been previously implicated in RNA nucleus͞cytoplasm distribution.…”

contrasting

confidence: 46%

See 1 more Smart Citation

Retrograde movement of tRNAs from the cytoplasm to the nucleus in Saccharomyces cerevisiae

Shaheen

Hopper

2005

Proc. Natl. Acad. Sci. U.S.A.

158

275

View full text Add to dashboard Cite

In eukaryotes, tRNAs transcribed in the nucleus function in cytoplasmic protein synthesis. The Ran-GTP-binding exportin, Los1p͞ Xpo-t, and additional pathway(s) mediate tRNA transport to the cytoplasm. Although tRNA movement was thought to be unidirectional, recent reports that yeast precursor tRNA splicing occurs in the cytoplasm, whereas fully spliced tRNAs can reside in the nucleus, require that either the precursor tRNA splicing machinery or mature tRNAs move from the cytoplasm to the nucleus. Our data argue against the first possibility and strongly support the second. Combining heterokaryon analysis with fluorescence in situ hybridization, we show that a foreign tRNA encoded by one nucleus can move from the cytoplasm to a second nucleus that does not encode the tRNA. We also discovered nuclear accumulation of endogenous cytoplasmic tRNAs in haploid yeast cells in response to nutritional deprivation. Nuclear accumulation of cytoplasmic tRNA requires Ran and the Mtr10͞Kap111 member of the importin-␤ family. Retrograde tRNA nuclear import may provide a novel mechanism to regulate gene expression in eukaryotes.amino acid deprivation ͉ heterokaryon ͉ Mtr10 ͉ tRNA nuclear import ͉ yeast E ukaryotic precursor tRNAs (pretRNAs) contain 5Ј and 3Ј extra sequences and, for Ϸ25% of Saccharomyces cerevisiae (yeast) tRNA families, introns. To be fully functional, pretRNAs are subject to several maturation steps, including removal of the extra sequences, numerous nucleoside modifications, and addition of the 3Ј terminal CCA nucleotides (1). In vertebrates, nearly all tRNA posttranscriptional processing occurs in the nucleus before export of tRNAs to the cytoplasm (1-3). In contrast, several lines of evidence show that in yeast, pretRNA intron removal occurs in the cytoplasm, not the nucleoplasm. First, the subunits of the heterotetrameric tRNA-specific splicing endonuclease, Sen15, Sen2, Sen34, and Sen54, colocalize with mitochondria (4, 5). Tethering of a noncatalytic subunit, Sen54, to mitochondria does not inhibit pretRNA splicing, whereas mutations prohibiting its mitochondrial association cause accumulation of unspliced pretRNAs (4). Moreover, cells with conditional mutations in a gene encoding a catalytic subunit, Sen2, accumulate unspliced pretRNAs in the cytoplasm (4). A previous report employing immunofluorescence and immune electron microscopy concluded that a large fraction of tRNA ligase, catalyzing second step of pretRNA splicing, resides in the nucleus (6); however, more recent reports show that there is a functional pool of tRNA ligase activity in the cytoplasm (7) and that carboxyl GFP-tagged ligase is cytosolic (5). Finally, a carboxyl GFP-tagged version of the enzyme catalyzing the third step of pretRNA splicing, removal of the residual 2Ј phosphate (8), is distributed throughout the cytoplasm (5).Splicing of pretRNAs in the cytoplasm provides an explanation for the pretRNA splicing defects observed when there are mutations in the tRNA nuclear export machinery, including the tRNA exportin, Los1p (9-11), ...

show abstract

contrasting

confidence: 46%

“…Interestingly, Mtr10 has been previously implicated in RNA nucleus͞cytoplasm distribution. It has a well-characterized role as the import receptor for the shuttling protein Npl3 involved in mRNA nuclear export (32). More relevant to our studies, Mtr10 was implicated in nuclear import of the RNA component of yeast telomerase, Tlc1 (33).…”

mentioning

confidence: 80%

Retrograde movement of tRNAs from the cytoplasm to the nucleus in Saccharomyces cerevisiae

Shaheen

Hopper

2005

Proc. Natl. Acad. Sci. U.S.A.

158

275

View full text Add to dashboard Cite

show abstract

“…Interaction of the karyopherin with RanGTP leads to dissociation of the karyopherin from its nuclear cargo (Weis, 2003;Harel and Forbes, 2004;Mosammaparast and Pemberton, 2004). In some circumstances, nuclear-binding partners of the cargo appear to also play a role in stimulating the dissociation of Kap and cargo (Senger et al, 1998;Lee and Aitchison, 1999;Pemberton et al, 1999). In yeast, there are 14 members of the karyopherin family, with Ͼ20 members in mammalian cells (Mosammaparast and Pemberton, 2004).…”

Section: Introductionmentioning

confidence: 99%

Nuclear Import of TFIIB Is Mediated by Kap114p, a Karyopherin with Multiple Cargo-binding Domains

Hodges

Leslie

Mosammaparast

et al. 2005

MBoC

View full text Add to dashboard Cite

Nuclear import and export is mediated by an evolutionarily conserved family of soluble transport factors, the karyopherins (referred to as importins and exportins). The yeast karyopherin Kap114p has previously been shown to import histones H2A and H2B, Nap1p, and a component of the preinitiation complex (PIC), TBP. Using a proteomic approach, we have identified several potentially new cargoes for Kap114p. These cargoes include another PIC component, the general transcription factor IIB or Sua7p, which interacted directly with Kap114p. Consistent with its role as a Sua7p import factor, deletion of KAP114 led to specific mislocalization of Sua7p to the cytoplasm. An interaction between Sua7p and TBP was also detected in cytosol, raising the possibility that both Sua7p and TBP can be coimported by Kap114p. We have also shown that Kap114p possesses multiple overlapping binding sites for its partners, Sua7p, Nap1p, and H2A and H2B, as well as RanGTP and nucleoporins. In addition, we have assembled an in vitro complex containing Sua7p, Nap1p, and histones H2A and H2B, suggesting that this Kap may import several proteins simultaneously. The import of more than one cargo at a time would increase the efficiency of each import cycle and may allow the regulation of coimported cargoes. INTRODUCTIONIn eukaryotic cells the nucleocytoplasmic transport of most proteins and some RNAs is mediated by an evolutionarily conserved family of soluble transport factors, the karyopherins (also referred to as importins and exportins; reviewed in Weis, 2003;Harel and Forbes, 2004;Mosammaparast and Pemberton, 2004). After synthesis in the cytoplasm, most nuclear protein cargoes are bound by a member of the karyopherin family, through direct interaction with a nuclear localization sequence contained in the cargo protein. Transport through the nuclear pore complex occurs via transient interactions of the karyopherin with the NPC. Once in the nucleus, the karyopherin encounters a high concentration of RanGTP, which acts as a regulator of transport. Interaction of the karyopherin with RanGTP leads to dissociation of the karyopherin from its nuclear cargo (Weis, 2003;Harel and Forbes, 2004;Mosammaparast and Pemberton, 2004). In some circumstances, nuclear-binding partners of the cargo appear to also play a role in stimulating the dissociation of Kap and cargo (Senger et al., 1998;Lee and Aitchison, 1999;Pemberton et al., 1999). In yeast, there are 14 members of the karyopherin family, with Ͼ20 members in mammalian cells (Mosammaparast and Pemberton, 2004). Karyopherins appear to function in either nuclear import or nuclear export, with only two examples of a Kap that works in both directions (Weis, 2003;Harel and Forbes, 2004;Mosammaparast and Pemberton, 2004). In yeast, 11 members of the karyopherin family must import at least 1500 nuclear proteins, suggesting that each receptor must have many cargoes. To date specific transport receptor-cargo pairs have only been shown for ϳ30 cargoes; in addition the NLS sequences recognized by most Kaps is n...

show abstract

“…Phosphorylation of the ASF/SF2 RS domain is required for nuclear import by Tnpo3 (23). Yeast, insect, and plant orthologs of Tnpo3 were similarly demonstrated to carry out nuclear import of SR and SR-like splicing factors (24)(25)(26).In addition to its role in nuclear import of splicing factors, Tnpo3 was implicated in HIV-1 infection (27)(28)(29). Although early reports proposed a direct interaction between Tnpo3 and HIV-1 integrase (29), subsequent genetic evidence strongly suggested a functional interplay between Tnpo3 and viral capsid Significance Transportin 3 (Tnpo3) was shown to orchestrate nuclear import of splicing factors over a decade ago, but how it recognizes these cargoes remained unknown.…”

mentioning

confidence: 99%

mentioning

confidence: 99%

Structural basis for nuclear import of splicing factors by human Transportin 3

Maertens

Cook

Wang

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

128

167

View full text Add to dashboard Cite

Transportin 3 (Tnpo3, Transportin-SR2) is implicated in nuclear import of splicing factors and HIV-1 replication. Herein, we show that the majority of cellular Tnpo3 binding partners contain arginineserine (RS) repeat domains and present crystal structures of human Tnpo3 in its free as well as GTPase Ran-and alternative splicing factor/splicing factor 2 (ASF/SF2)-bound forms. The flexible β-karyopherin fold of Tnpo3 embraces the RNA recognition motif and RS domains of the cargo. A constellation of charged residues on and around the arginine-rich helix of Tnpo3 HEAT repeat 15 engage the phosphorylated RS domain and are critical for the recognition and nuclear import of ASF/SF2. Mutations in the same region of Tnpo3 impair its interaction with the cleavage and polyadenylation specificity factor 6 (CPSF6) and its ability to support HIV-1 replication. Steric incompatibility of the RS domain and RanGTP engagement by Tnpo3 provides the mechanism for cargo release in the nucleus. Our results elucidate the structural bases for nuclear import of splicing factors and the Tnpo3-CPSF6 nexus in HIV-1 biology.T he transport of macromolecules between cytoplasm and nucleus is orchestrated by a family of nuclear import and export receptors (1). Referred to as importins and exportins, these proteins bind their specific cargoes and translocate them across the nuclear pore complex. The process is regulated by the small GTPase Ran that partitions between cytoplasm and nucleus in the predominantly GDP-and GTP-bound form, respectively. Importins associate with their cargoes in the cytoplasm, and the competitive binding of RanGTP induces them to release their cargoes in the nucleus (2). Most nuclear import/export receptors belong to the β-karyopherin family of proteins, with 22 members encoded in the human genome (3). The majority of β-karyopherins bind their cargoes directly, recognizing a linear nuclear localization or export signal and/or a specific tertiary/quaternary structural feature (4, 5).A fundamentally important type of a nuclear localization signal (NLS), comprising sequences rich in Arg-Ser and/or ArgAsp/Glu/Gly dipeptides (referred to as RS or RS-like domains), belongs to the family of Ser/Arg-rich (SR) proteins. These nuclear proteins also contain RNA recognition motif (RRM) domains and play essential roles in pre-mRNA splicing and 3′ processing and participate in transcription regulation, mRNA transport, translation, and nonsense-mediated mRNA decay (6). The splicing factors alternative splicing factor/splicing factor 2 (ASF/SF2) and SC35 along with the cleavage and polyadenylation specificity factor 6 (CPSF6, also known as CF-Im-68) are among the best-characterized metazoan SR proteins (7-10). The SR protein family can be further extended by inclusion of a structurally and functionally diverse group of nuclear proteins that possess RS repeats but lack RRM domains (11). The RS domains are processively phosphorylated on their Ser residues by a set of dedicated kinases (12-16). Phosphorylation of SR proteins is thought to...

show abstract

Mtr10p functions as a nuclear import receptor for the mRNA-binding protein Npl3p

Cited by 178 publications

References 62 publications

Retrograde movement of tRNAs from the cytoplasm to the nucleus in Saccharomyces cerevisiae

Retrograde movement of tRNAs from the cytoplasm to the nucleus in Saccharomyces cerevisiae

Nuclear Import of TFIIB Is Mediated by Kap114p, a Karyopherin with Multiple Cargo-binding Domains

Structural basis for nuclear import of splicing factors by human Transportin 3

Contact Info

Product

Resources

About