Demonstration of a 7-nm RNP fiber as the basic structural element in a premessenger RNP particle

Lönnroth, Anna; Alexciev, Krassimir; Mehlin, Hans; Wurtz, Tilmann; Skoglund, Ulf; Daneholt, Bertil

doi:10.1016/0014-4827(92)90437-d

Cited by 34 publications

(22 citation statements)

References 20 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…It has previously been proposed that the 7-nm RNP fiber consists of a filamentous core of proteins with the RNA molecule spooled around the core (for a discussion, see reference 22). hnRNP proteins are known to bind to RNA with a certain degree of sequence preference (see the introduction), and therefore it is likely that hrp36 and hrp45 are not randomly binding to the 35-to 40-kb BR transcripts.…”

Section: Discussionmentioning

confidence: 99%

“…The higher-order structure of the BR particle is well-defined, and it seems likely that the folding is determined by specific molecular interactions. As the fiber can be completely unfolded at moderately low ionic strength with the proteins still associated with the RNA (22), the bonds are not likely to be covalent in nature. It remains to be elucidated whether the 36-and 45-kDa proteins also participate in the organization of this higherorder structure.…”

Section: Discussionmentioning

confidence: 99%

“…BR granules were extracted from salivary glands and collected as a 300S fraction after centrifugation in a sucrose gradient prepared in TKE (10 mM triethanolamine-Cl [pH 7.0], 100 mM KCl, 10 mM EDTA) (47). This particle preparation was diluted 10-fold with distilled water and incubated for 15 min at 5ЊC to partly unfold the tightly packed RNP fiber (22). Glutaraldehyde was added to a final concentration of 2%, and the particle solution was placed in microchambers with carbon-coated, glow-discharged electron microscope grids on the bottom and centrifuged in a tabletop centrifuge at 4ЊC for 15 min at 20,000 ϫ g. After centrifugation, the grids were washed in a 1/10 dilution of TKE (1/10 TKE) and floated on a 20-l drop of 1% BSA in 1/10 TKE for 20 min at room temperature in a humid chamber.…”

Section: Sds-page Of Proteins and Western Blottingmentioning

confidence: 99%

“…It has been shown by electron microscope tomography that the released BR particle attains a ring-like conformation with four distinct domains (39). The primary element is a 7-nm RNP fiber, which is folded in a specific manner to form the ring-like structure (22). When passing through the pore, the particle changes conformation and traverses the pore as a ribbon with the 5Ј end of the transcript in the lead (26).…”

mentioning

confidence: 99%

See 3 more Smart Citations

Identification of Two RNA-Binding Proteins in Balbiani Ring Premessenger Ribonucleoprotein Granules and Presence of These Proteins in Specific Subsets of Heterogeneous Nuclear Ribonucleoprotein Particles

Wurtz-T

Kiseleva

Nacheva

et al. 1996

Molecular and Cellular Biology

View full text Add to dashboard Cite

Balbiani ring (BR) granules are premessenger ribonucleoprotein particles (RNPs) generated in giant chromosomal puffs, the BRs, in the larval salivary glands of the dipteran Chironomus tentans. Monoclonal antibodies were raised against nuclear proteins collected on a single-stranded-DNA-agarose affinity column, and two of them were used to identify RNA-binding proteins in BR granules. First, in Western blots (immunoblots), one of the antibodies recognized a 36-kDa protein and the other recognized a 45-kDa protein. Second, both antibodies bound to the BRs in immunocytological experiments. It was shown in cross-linking experiments that the two proteins are associated with heterogeneous nuclear RNP (hnRNP) complexes extracted from C. tentans nuclei. By immunoelectron microscopy of isolated and partly unfolded BR RNPs, it was specifically demonstrated that the BR granules contain the two proteins and, in addition, that both proteins are distributed frequently along the RNP fiber of the particles. Thus, the 36-and 45-kDa proteins are likely to be abundant, RNA-binding proteins in the BR particles. To elucidate to what extent the two proteins are also present in other hnRNPs, we studied the binding of the antibodies to chromosomal puffs in general. It was observed that many puffs in addition to the BRs harbor the two proteins, but there are also puffs containing only one of the components, either the 36-or the 45-kDa protein. We conclude that the two proteins are not randomly bound to all hnRNPs but that each of them seems to be linked to a specific subset of the particles.The nuclear precursors of mRNA, often designated hnRNA (heterogeneous nuclear RNA), are associated with proteins to form heterogeneous nuclear ribonucleoprotein particles (hnRNPs) (8, 10, 11). The hnRNP proteins constitute a major fraction of the nuclear proteins; in growing cells, they are as abundant as the histone proteins (18). They bind to the RNA concomitantly with transcription (12, 27) and are generally assumed to be confined to the cell nucleus (17, 35), although some of them have recently been shown to shuttle between the nucleus and the cytoplasm (34). The hnRNP population is complex; for example, there are about 20 major and a large number of minor hnRNP proteins in humans (33; see also reference 16). The hnRNP proteins contain a modular structure with one or more RNA-binding domains and at least one auxiliary domain that is probably involved in protein-protein interactions (for a recent review, see reference 11).hnRNP proteins have a general RNA-binding ability, but more and more information indicating that the proteins bind preferentially to distinct RNA sequences is accumulating. For example, the binding of several hnRNP proteins to different ribohomopolymers was studied, and it was found that various hnRNP proteins show different relative affinities for the ribonucleotide homopolymers (42). The hnRNP C proteins recognize a binding site consisting of five uridines in pre-mRNA polyadenylation substrates (28,46). The polypyrimidine tract...

show abstract

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Sds-page Of Proteins and Western Blottingmentioning

confidence: 99%

mentioning

confidence: 99%

See 2 more Smart Citations

Identification of Two RNA-Binding Proteins in Balbiani Ring Premessenger Ribonucleoprotein Granules and Presence of These Proteins in Specific Subsets of Heterogeneous Nuclear Ribonucleoprotein Particles

Wurtz-T

Kiseleva

Nacheva

et al. 1996

Molecular and Cellular Biology

View full text Add to dashboard Cite

show abstract

“…In C. tentans salivary gland cells, transcripts from the BR1 and BR2 genes form 7 nm thick RNA-protein fibers which fold into mRNP particles with a diameter of 50 nm (Lönnroth et al, 1992). These mRNP particles are morphologically distinguishable as they are synthesized on the gene and as they subsequently are transported through the interchromatin.…”

Section: Journal Of Cell Science 116 (22)mentioning

confidence: 99%

TheChironomus tentanstranslation initiation factor eIF4H is present in the nucleus but does not bind to mRNA until the mRNA reaches the cytoplasmic perinuclear region

Björk

Baurén²,

Gelius

et al. 2003

Journal of Cell Science

View full text Add to dashboard Cite

In the cell nucleus, precursors to mRNA, pre-mRNAs, associate with a large number of proteins and are processed to mRNA-protein complexes, mRNPs. The mRNPs are then exported to the cytoplasm and the mRNAs are translated into proteins. The mRNAs containing in-frame premature stop codons are recognized and degraded in the nonsense-mediated mRNA decay process. This mRNA surveillence may also occur in the nucleus and presumably involves components of the translation machinery. Several translation factors have been detected in the nucleus, but their functional relationship to the dynamic protein composition of pre-mRNPs and mRNPs in the nucleus is still unclear. Here, we have identified and characterized the translation initiation factor eIF4H in the dipteran Chironomus tentans. In the cytoplasm, Ct-eIF4H is associated with poly(A+) RNA in polysomes. We show that a minor fraction of Ct-eIF4H enters the nucleus. This fraction is independent on the level of transcription. CteIF4H could not be detected in gene-specific pre-mRNPs or mRNPs, nor in bulk mRNPs in the nucleus. Our immunoelectron microscopy data suggest that Ct-eIF4H associates with mRNP in the cytoplasmic perinuclear region, immediately as the mRNP exits from the nuclear pore complex.

show abstract

Ribonucleoprotein ( RNP )

Sperling¹,

Sperling²

2002

Encyclopedia of Molecular Biology

View full text Add to dashboard Cite

Demonstration of a 7-nm RNP fiber as the basic structural element in a premessenger RNP particle

Cited by 34 publications

References 20 publications

Identification of Two RNA-Binding Proteins in Balbiani Ring Premessenger Ribonucleoprotein Granules and Presence of These Proteins in Specific Subsets of Heterogeneous Nuclear Ribonucleoprotein Particles

Identification of Two RNA-Binding Proteins in Balbiani Ring Premessenger Ribonucleoprotein Granules and Presence of These Proteins in Specific Subsets of Heterogeneous Nuclear Ribonucleoprotein Particles

TheChironomus tentanstranslation initiation factor eIF4H is present in the nucleus but does not bind to mRNA until the mRNA reaches the cytoplasmic perinuclear region

Ribonucleoprotein ( RNP )

Contact Info

Product

Resources

About