Faculty Opinions recommendation of Nuclear RNP complex assembly initiates cytoplasmic RNA localization.

Cytoplasmic localization of mRNAs is a widespread mechanism for generating cell polarity and can provide the basis for patterning during embryonic development. A prominent example of this is localization of maternal mRNAs in Xenopus oocytes, a process requiring recognition of essential RNA sequences by protein components of the localization machinery. However, it is not yet clear how and when such protein factors associate with localized RNAs to carry out RNA transport. To trace the RNA–protein interactions that mediate RNA localization, we analyzed RNP complexes from the nucleus and cytoplasm. We find that an early step in the localization pathway is recognition of localized RNAs by specific RNA-binding proteins in the nucleus. After transport into the cytoplasm, the RNP complex is remodeled and additional transport factors are recruited. These results suggest that cytoplasmic RNA localization initiates in the nucleus and that binding of specific RNA-binding proteins in the nucleus may act to target RNAs to their appropriate destinations in the cytoplasm.

Download Full-text

PTB/hnRNP I Is Required for RNP Remodeling during RNA Localization in Xenopus Oocytes

Molecular and Cellular Biology ◽

10.1128/mcb.00999-07 ◽

2007 ◽

Vol 28 (2) ◽

pp. 678-686 ◽

Cited By ~ 29

Author(s):

Raymond A. Lewis ◽

James A. Gagnon ◽

Kimberly L. Mowry

Keyword(s):

Protein Interactions ◽

Xenopus Oocytes ◽

Rna Binding ◽

Rna Binding Proteins ◽

Rna Localization ◽

Rna Transport ◽

Rna Sequences ◽

Cytoplasmic Rna ◽

Embryonic Polarity ◽

Specific Mrnas

ABSTRACT Transport of specific mRNAs to defined regions within the cell cytoplasm is a fundamental mechanism for regulating cell and developmental polarity. In the Xenopus oocyte, Vg1 RNA is transported to the vegetal cytoplasm, where localized expression of the encoded protein is critical for embryonic polarity. The Vg1 localization pathway is directed by interactions between key motifs within Vg1 RNA and protein factors recognizing those RNA sequences. We have investigated how RNA-protein interactions could be modulated to trigger distinct steps in the localization pathway and found that the Vg1 RNP is remodeled during cytoplasmic RNA transport. Our results implicate two RNA-binding proteins with key roles in Vg1 RNA localization, PTB/hnRNP I and Vg1RBP/vera, in this process. We show that PTB/hnRNP I is required for remodeling of the interaction between Vg1 RNA and Vg1RBP/vera. Critically, mutations that block this remodeling event also eliminate vegetal localization of the RNA, suggesting that RNP remodeling is required for localization.

Download Full-text

Me31B silences translation of oocyte-localizing RNAs through the formation of cytoplasmic RNP complex duringDrosophilaoogenesis

Development ◽

10.1242/dev.128.17.3233 ◽

2001 ◽

Vol 128 (17) ◽

pp. 3233-3242 ◽

Cited By ~ 17

Author(s):

Akira Nakamura ◽

Reiko Amikura ◽

Kazuko Hanyu ◽

Satoru Kobayashi

Keyword(s):

Translational Control ◽

Rna Localization ◽

Rna Transport ◽

Nurse Cells ◽

Embryonic Patterning ◽

Maternal Factors ◽

Dead Box ◽

Rnp Complex

Embryonic patterning in Drosophila is regulated by maternal factors. Many such factors become localized as mRNAs within the oocyte during oogenesis and are translated in a spatio-temporally regulated manner. These processes are controlled by trans-acting proteins, which bind to the target RNAs to form a ribonucleoprotein (RNP) complex. We report that a DEAD-box protein, Me31B, forms a cytoplasmic RNP complex with oocyte-localizing RNAs and Exuperantia, a protein involved in RNA localization. During early oogenesis, loss of Me31B causes premature translation of oocyte-localizing RNAs within nurse cells, without affecting their transport to the oocyte. These results suggest that Me31B mediates translational silencing of RNAs during their transport to the oocyte. Our data provide evidence that RNA transport and translational control are linked through the assembly of RNP complex.

Download Full-text