HEL/UAP56 Binds Cotranscriptionally to the Balbiani Ring Pre-mRNA in an Intron-Independent Manner and Accompanies the BR mRNP to the Nuclear Pore

Kiesler, Eva; Miralles, Francesc; Visa, Neus

doi:10.1016/s0960-9822(02)00840-0

Cited by 54 publications

(45 citation statements)

References 21 publications

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“…Therefore, export adaptors play a central role in remodeling the protein-mRNA interactions within the mRNA export complex during transport from the nucleus to the cytoplasm. This situation is similar to that found in yeast and is consistent with electron microscopy data from Chironomus tentans, indicating that UAP56 is displaced from the mRNP before REF (10).…”

Section: Discussionsupporting

confidence: 90%

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Mutually exclusive interactions drive handover of mRNA from export adaptors to TAP

Hautbergue

Hung

Golovanov

et al. 2008

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

162

226

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REF/Yra1p interacts with TAP/Mex67p, and in yeast this interaction leads to displacement of Sub2p from Yra1p (7). TAP heterodimerizes with p15 and binds nucleoporins through central and C-terminal domains (8), directing the mRNP to the nuclear pore and promoting transport to the cytoplasm. On the cytoplasmic side of the nuclear pore, Dbp5p triggers displacement of Mex67p from mRNA. Yra1p binds mRNA early during its nuclear maturation but is no longer bound once it reaches the nuclear periphery (9). Consistent with this finding, analysis of Balbiani ring pre-mRNPs shows that UAP56 and REF accompany the mRNP to the nuclear periphery where UAP56 and then REF dissociate during translocation through the pore (10).Although Yra1p is essential for yeast mRNA export, depletion of REF in higher eukaryotes does not block bulk mRNA export (11), suggesting that other proteins can fulfill this role and that there may be functional redundancy between export adaptors. The shuttling SR proteins 9G8, SRp20, and SF2/ASF directly bind TAP by short arginine-rich peptides (12, 13) and can function as export factors (14). Even in yeast, other proteins can recruit Mex67p to the mRNP, including Yra2p (15) and Npl3p.The fact that TAP binds RNA weakly in vitro led to the idea that export factors such as REF, which bind RNA avidly, bridge the interaction between TAP and mRNA, leading to the term mRNA export adaptors (15). However, both TAP and Mex67p are readily UV-cross-linked to mRNA in vivo (16)(17)(18), suggesting a direct stable interaction at some point during export. Here, we show that mRNA is handed over from export adaptors to TAP and that at least in vitro, export adaptors have the ability to enhance the RNA-binding activity of TAP. ResultsThe RNA-and TAP-Binding Sites on REF Overlap. In Saccharomyces cerevisiae, Mex67p binding to Yra1p triggers displacement of Sub2p (7), so we established whether this is the case for the mammalian orthologs. We examined whether UAP56 coimmunoprecipitated (Co-IP) with REF2-I (REF) in the presence of increasing amounts of TAP. This analysis revealed that TAP triggered dissociation of UAP56 from REF (Fig. 1A, lanes 5 and 6).We analyzed organization of the resulting REF-TAP-RNA ternary complex by examining how REF binds RNA. NMR

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Section: Discussionsupporting

confidence: 90%

“…Yra1p binds mRNA early during its nuclear maturation but is no longer bound once it reaches the nuclear periphery (9). Consistent with this finding, analysis of Balbiani ring pre-mRNPs shows that UAP56 and REF accompany the mRNP to the nuclear periphery where UAP56 and then REF dissociate during translocation through the pore (10).…”

mentioning

confidence: 61%

Mutually exclusive interactions drive handover of mRNA from export adaptors to TAP

Hautbergue

Hung

Golovanov

et al. 2008

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

162

226

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“…These results are consistent with Uap56p shuttling between the two cellular compartments. Notably the Chironomus tentans homolog of Uap56p, HEL, was shown to co-migrate with exporting mRNPs and was seen to be released within the nuclear pores prior to the release of Aly (31). Taken together, our results suggest that Uap56p likely functions as an mRNA export carrier in S. pombe.…”

Section: Discussionmentioning

confidence: 55%

The Nuclear Export Signal of Splicing Factor Uap56p Interacts with Nuclear Pore-associated Protein Rae1p for mRNA Export in Schizosaccharomyces pombe

Thakurta¹,

Selvanathan²,

Patterson

et al. 2007

Journal of Biological Chemistry

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Mammalian UAP56 or its homolog Sub2p in Saccharomyces cerevisiae are members of the ATP-dependent RNA helicase family and are required for splicing and nuclear export of mRNA. Previously we showed that in Schizosaccharomyces pombe Uap56p is critical for mRNA export. It links the mRNA adapter Mlo3p, a homolog of Yra1p in S. cerevisiae or Aly in mammals, to nuclear pore-associated mRNA export factor Rae1p. In this study we show that, in contrast to S. cerevisiae, Uap56p in S. pombe is not required for pre-mRNA splicing. The putative RNA helicase function of Uap56p is not required for mRNA export. However, the RNAbinding motif of Uap56p is critical for nuclear export of mRNA. Within Uap56p we identified nuclear import and export signals that may allow it to shuttle between the nucleus and the cytoplasm. We found that Uap56p interacts with Rae1p directly via its nuclear export signal, and this interaction is critical for the nuclear export activity of Uap56p as well as for exporting mRNA. RNA binding and the ability to shuttle between the nucleus and cytoplasm are important features of mRNA export carriers such as HIV-Rev. Our results suggest that Uap56p could function similarly as an export carrier of mRNA in S. pombe.Mammalian UAP56 (Saccharomyces cerevisiae Sub2p) and its functional homologs belong to the conserved DECD box class of ATP-dependent RNA helicases that play important functional roles in multiple aspects of DNA and RNA metabolism (1). They are essential in a number of organisms, including yeast, nematode, and fruit fly (2). UAP56/Sub2p is directly involved in pre-messenger RNA splicing and nuclear export of messenger RNAs in S. cerevisiae and in metazoan cells (3). Recently, in Schizosaccharomyces pombe, we found that uap56 is an essential gene for growth and that Uap56p is critical for mRNA export (4). Mammalian UAP56 functions in both ATP-independent and ATP-dependent steps of the spliceosome assembly process (5). Uap56p homologs typically contain a characteristic ATP-binding site, a catalytic DECD box, and an RNA interaction motif. Mutations within the ATP-binding pocket or the catalytic DECD box residues abolished the splicing functions of UAP56 (5).

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“…This argues that the accumulation of EJC proteins at transcription sites requires efficient pre-mRNA processing. However, there is previous evidence indicating that REF/Aly can associate with the region 20-24 nucleotides upstream of exon-exon junctions independent of splicing (Reichert et al 2002), that UAP56 binds to nascent transcripts independent of the localization of introns (Kiesler et al 2002), and that both REF/Aly and UAP56 are part of the TREX (transcription/export) complex, which is thought to be recruited during transcription (Strasser et al 2002). Possibly, in our microscopic assay we fail to visualize proteins that are loosely associated with the RNA and detect only stable complexes.…”

Section: Custó Dio Et Almentioning

confidence: 99%

In vivo recruitment of exon junction complex proteins to transcription sites in mammalian cell nuclei

Custódio

Carvalho²,

Condado³

et al. 2004

RNA

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HEL/UAP56 Binds Cotranscriptionally to the Balbiani Ring Pre-mRNA in an Intron-Independent Manner and Accompanies the BR mRNP to the Nuclear Pore

Cited by 54 publications

References 21 publications

Mutually exclusive interactions drive handover of mRNA from export adaptors to TAP

Mutually exclusive interactions drive handover of mRNA from export adaptors to TAP

The Nuclear Export Signal of Splicing Factor Uap56p Interacts with Nuclear Pore-associated Protein Rae1p for mRNA Export in Schizosaccharomyces pombe

In vivo recruitment of exon junction complex proteins to transcription sites in mammalian cell nuclei

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