Evidence for involvement of a nuclear envelope‐associated RNA helicase activity in nucleocytoplasmic RNA transport

Schröder, Heinz C.; Ugarković, Đurđica; Langen, P.; Bachmann, Michael; Dorn, August; Kuchino, Yoshiyuki; Müller, Wernér E.G.

doi:10.1002/jcp.1041450119

Cited by 9 publications

(2 citation statements)

References 48 publications

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“…Two other proteins (Mtr13p/Nab1p/Np13p/Nop3p and Nup145p) implicated in RNA export do have complete or partial RNA recognition motifs (4,8,31,39). Possibly related helicase activities have also been detected in the rat liver and in HeLa cell nuclei (10,21,36).…”

Section: Discussionmentioning

confidence: 99%

A DEAD-Box-Family Protein Is Required for Nucleocytoplasmic Transport of Yeast mRNA

Liang

Hitomi

et al. 1996

Molecular and Cellular Biology

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An enormous variety of primary and secondary mRNA structures are compatible with export from the nucleus to the cytoplasm. Therefore, there seems to be a mechanism for RNA export which is independent of sequence recognition. There nevertheless is likely to be some relatively uniform mechanism which allows transcripts to be packaged as ribonucleoprotein particles, to gain access to the periphery of the nucleus and ultimately to translocate across nuclear pores. To study these events, we and others have generated temperature-sensitive recessive mRNA transport (mtr) mutants of Saccharomyces cerevisiae which accumulate poly(A)؉ RNA in the nucleus at 37؇C. Several of the corresponding genes have been cloned. Upon depletion of one of these proteins, Mtr4p, conspicuous amounts of nuclear poly(A)؉ RNA accumulate in association with the nucleolus. Corresponding dense material is also seen by electron microscopy. MTR4 is essential for growth and encodes a novel nuclear protein with a size of ϳ120 kDa. Mtr4p shares characteristic motifs with DEAD-box RNA helicases and associates with RNA. It therefore may well affect RNA conformation. It shows extensive homology to a human predicted gene product and the yeast antiviral protein Ski2p. Critical residues of Mtr4p, including the mtr4-1 point mutation, have been identified. Mtr4p may serve as a chaperone which translocates or normalizes the structure of mRNAs in preparation for export.The mechanism of export of mRNA from the nucleus to the cytoplasm is remarkably accommodating in the sense that an enormous variety of primary and secondary RNA structures are compatible with export. The fact that neither the 5Ј methyl cap structure nor the 3Ј poly(A) tail appears altogether essential for export (16) suggests that there is a mechanism in the nucleus which allows for RNA recognition independent of the sequence. It is likely that during or immediately after their synthesis, transcripts are quickly packaged into ribonucleoprotein particles (RNP) which enable them to gain access to the periphery of the nucleoplasm and interact specifically with components of nuclear pores, through which they subsequently translocate (14,42). If this itinerary is relatively uniform for most mRNAs, it is reasonable to postulate that there are factors which serve as RNA chaperones and/or normalize RNA secondary structure. Single-stranded RNAs spontaneously acquire an extensive secondary structure, which is subject to proteins with annealing activity (p53 and heterogeneous nuclear RNP [hnRNP] A1 [24,25]) and melting activity (helicases [34]). Studies of the yeast Saccharomyces cerevisiae have identified several proteins which, when mutated, lead to nuclear accumulation of poly(A) ϩ RNA without inhibiting pre-mRNA splicing. Apart from nucleoporins (8), these includes components of a nucleocytoplasmic GTPase cycle [the Cnr1/2p (Gsp1/2p) GTPases, Mtr1p (Prp20p), and Rna1p (6, 35)], a cytoplasmic protein (Mtr7p [34a]), the nucleolar protein Mtr3p (19), the nuclear proteins Mtr2p (19) and Rat1p (1), and the ...

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Section: Discussionmentioning

confidence: 99%

A DEAD-Box-Family Protein Is Required for Nucleocytoplasmic Transport of Yeast mRNA

Liang

Hitomi

et al. 1996

Molecular and Cellular Biology

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“…Like nuclear transport of proteins, RNA transport is an active, signal-directed, and vectorial process (Dargemont & Kuhn, 1992;Zapp, 1992). Nucleoside triphosphatase (NTPase) and RNA helicase (RNA duplex unwindase) have been found to be associated with the nuclear envelope and be involved in nuclear export of RNA (Schroder et al, 1986(Schroder et al, , 1990.…”

Section: A Surface Viewmentioning

confidence: 99%

Plasmodesmata and the supracellular nature of plants

1993

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SUMMARY In the classical formulation of Münch (1930), plasmodesmata are considered to form simple cytoplasmic bridges between neighbouring plant cells to create the symplasm. This concept has dominated, if not monopolized, the thinking of plant biologists and in particular plant physiologists over the last few decades. Recent advances in ultrastructural, physiological and molecular studies on plasmodesmata indicate that this simple view is in need of revision. Structurally, the higher plant plasmodesma has been revealed to be a supramolecular complex consisting of membranes and proteins. Functionally, evidence is at hand that this complex structure appears to have evolved not only to control the size exclusion limit for intercellular diffusion of metabolites and small molecules, but also to potentiate and regulate intercellular trafficking of macromolecules, including proteins and nucleic acids. In this regard, plasmodesmal transport may share parallel regulatory mechanisms with nucleocytoplasmic transport. Based on these findings, we advance the hypothesis that plants function as supracellular, rather than multicellular, organisms. As such, the dynamics of the plant body, including cell differentiation, tissue formation, organogenesis and specialized physiological function(s), is subject to plasmodesmal regulation. Plasmodesmata presumably accomplish such regulatory roles by trafficking informational molecules which orchestrate both metabolic activity and gene expression. Current and future studies on the evolutionary origin(s) of plasmodesmata are likely to provide valuable information in terms of the genetic and molecular basis for the supracellular nature of plants.

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Changes of Nuclear Membrane Lipid Composition Affect RNA Nucleocytoplasmic Transport

Tomassoni

Amori

Magni

1999

Biochemical and Biophysical Research Communications

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Evidence for involvement of a nuclear envelope‐associated RNA helicase activity in nucleocytoplasmic RNA transport

Cited by 9 publications

References 48 publications

A DEAD-Box-Family Protein Is Required for Nucleocytoplasmic Transport of Yeast mRNA

A DEAD-Box-Family Protein Is Required for Nucleocytoplasmic Transport of Yeast mRNA

Plasmodesmata and the supracellular nature of plants

Changes of Nuclear Membrane Lipid Composition Affect RNA Nucleocytoplasmic Transport

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