1
|
Levadoux M, Mahon C, Beattie JH, Wallace HM, Hesketh JE. Nuclear import of metallothionein requires its mRNA to be associated with the perinuclear cytoskeleton. J Biol Chem 1999; 274:34961-6. [PMID: 10574972 DOI: 10.1074/jbc.274.49.34961] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The influence of mRNA localization on metallothionein-1 protein distribution was studied by immunocytochemistry. We used Chinese hamster ovary cells that had been transfected with either a native metallothionein-1 gene construct or metallothionein-1 5'-untranslated region and coding sequences linked to the 3'-untranslated region from glutathione peroxidase. The change in the 3'-untranslated region caused the delocalization of the mRNA with a loss of the perinuclear localization and association with the cytoskeleton. Clones were selected which expressed similar levels of metallothionein-1 protein, as assessed by radioimmunoassay. The results showed that loss of metallothionein-1 mRNA localization was associated with a loss of metallothionein-1 protein localization, most notably with a lack of metallothionein-1 protein in the nucleus of synchronized cells which were beginning to synthesize DNA. This indicates that the association of metallothionein-1 mRNA with the cytoskeleton around the nucleus is essential for efficient shuttling of the protein into the nucleus during the G(1) to S phase transition. This is the first demonstration of a physiological role for perinuclear mRNA localization and we propose that such localization may be important for a wide range of nuclear proteins, including those that shuttle between nucleus and cytoplasm in a cell cycle dependent manner.
Collapse
Affiliation(s)
- M Levadoux
- Rowett Research Institute, Greenburn Road, Bucksburn, Aberdeen AB21 9SB, United Kingdom
| | | | | | | | | |
Collapse
|
2
|
Boccaccio GL, Carminatti H, Colman DR. Subcellular fractionation and association with the cytoskeleton of messengers encoding myelin proteins. J Neurosci Res 1999; 58:480-91. [PMID: 10533041 DOI: 10.1002/(sici)1097-4547(19991115)58:4<480::aid-jnr2>3.0.co;2-z] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The targeting of polypeptides to restricted cytoplasmic domains by means of mRNA sorting is a widespread phenomena utilized by many cell types. In the central nervous system, in situ hybridization analysis has shown previously that the mRNAs encoding several myelin-specific proteins are specifically located within the myelinating processes of oligodendrocytes. Here, by means of biochemical and subcellular fractionation methods, we show that a myelin fraction is selectively enriched in those mRNAs. The four major myelin basic protein (MBP) mRNAs that arise by alternative splicing of exons II and VI of the MBP gene are concentrated in this subcellular fraction. Furthermore, an interaction of MBP and MOBP 81A mRNAs with the cytoskeleton was observed. This interaction might serve to mediate the anchoring of these messengers after translocation to the subcellular site of translation.
Collapse
Affiliation(s)
- G L Boccaccio
- Instituto de Investigaciones Bioquímicas "Fundación Campomar" and Facultad de Ciencias Exactas y Naturales, UBA, Buenos Aires, Argentina.
| | | | | |
Collapse
|
3
|
Ruzanov PV, Evdokimova VM, Korneeva NL, Hershey JW, Ovchinnikov LP. Interaction of the universal mRNA-binding protein, p50, with actin: a possible link between mRNA and microfilaments. J Cell Sci 1999; 112 ( Pt 20):3487-96. [PMID: 10504297 DOI: 10.1242/jcs.112.20.3487] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We have shown previously that p50 is the most abundant protein associated with a variety of eukaryotic mRNAs and exhibits about 98% amino acid sequence identity to mammalian Y-box binding transcription factors. The dual function of p50 in the cell as a regulator of both transcription and translation has been suggested. To gain insight into the role of p50 in these processes, we performed the yeast two-hybrid screen to identify p50 molecular partners. Here we report the identification of actin as a p50-interacting protein. Coimmunoprecipitation of p50 and actin from HeLa extracts as well as in vitro binding studies indicate specificity and a high affinity for the interaction between p50 and actin. Interestingly, p50 binding to actin is affected by mRNA; binding was observed at a low p50/mRNA ratio and was greatly reduced at higher ratios. Since the p50/mRNA ratio appears to be important for mRNA translatability, we speculate that p50 can regulate the attachment of mRNA to the actin network depending on its translational activity. Using immunofluorescence, we show that p50 binds to actin filaments in permeabilized cells and causes actin fibers to bundle in vitro. Together, these findings support the view that p50 may play an important role in mRNA transport, anchoring, and localization on actin filaments in the cell.
Collapse
Affiliation(s)
- P V Ruzanov
- Institute of Protein Research, Russian Academy of Sciences, Pushchino, Moscow Region, Russian Federation.
| | | | | | | | | |
Collapse
|
4
|
Muench DG, Wu Y, Coughlan SJ, Okita TW. Evidence for a Cytoskeleton-Associated Binding Site Involved in Prolamine mRNA Localization to the Protein Bodies in Rice Endosperm Tissue. PLANT PHYSIOLOGY 1998; 116:559-69. [PMID: 9490759 PMCID: PMC35113 DOI: 10.1104/pp.116.2.559] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/1997] [Accepted: 10/26/1997] [Indexed: 05/21/2023]
Abstract
Previous studies have demonstrated that the mRNAs encoding the prolamine and glutelin storage proteins are localized to morphologically distinct membranes of the endoplasmic reticulum (ER) complex in developing rice (Oryza sativa L.) endosperm cells. To gain insight about this mRNA localization process, we investigated the association of prolamine polysomes on the ER that delimit the prolamine protein bodies (PBs). The bulk of the prolamine polysomes were resistant to extraction by 1% Triton X-100 either alone or together with puromycin, which suggests that these translation complexes are anchored to the PB surface through a second binding site in addition to the well-characterized ribosome-binding site of the ER-localized protein translocation complex. Suppression of translation initiation shows that these polysomes are bound through the mRNA, as shown by the simultaneous increase in the amounts of ribosome-free prolamine mRNAs and decrease in prolamine polysome content associated with the membrane-stripped PB fraction. The prolamine polysome-binding activity is likely to be associated with the cytoskeleton, based on the association of actin and tubulin with the prolamine polysomes and PBs after sucrose-density centrifugation.
Collapse
Affiliation(s)
- DG Muench
- Institute of Biological Chemistry, Washington State University, Pullman, Washington 99164-6340 (D.G.M., Y.W., T.W.O.)
| | | | | | | |
Collapse
|
5
|
Murray JW, Edmonds BT, Liu G, Condeelis J. Bundling of actin filaments by elongation factor 1 alpha inhibits polymerization at filament ends. J Cell Biol 1996; 135:1309-21. [PMID: 8947553 PMCID: PMC2121097 DOI: 10.1083/jcb.135.5.1309] [Citation(s) in RCA: 86] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Elongation factor 1 alpha (EF1 alpha) is an abundant protein that binds aminoacyl-tRNA and ribosomes in a GTP-dependent manner. EF1 alpha also interacts with the cytoskeleton by binding and bundling actin filaments and microtubules. In this report, the effect of purified EF1 alpha on actin polymerization and depolymerization is examined. At molar ratios present in the cytosol, EF1 alpha significantly blocks both polymerization and depolymerization of actin filaments and increases the final extent of actin polymer, while at high molar ratios to actin, EF1 alpha nucleates actin polymerization. Although EF1 alpha binds actin monomer, this monomer-binding activity does not explain the effects of EF1 alpha on actin polymerization at physiological molar ratios. The mechanism for the inhibition of polymerization is related to the actin-bundling activity of EF1 alpha. Both ends of the actin filament are inhibited for polymerization and both bundling and the inhibition of actin polymerization are affected by pH within the same physiological range; at high pH both bundling and the inhibition of actin polymerization are reduced. Additionally, it is seen that the binding of aminoacyl-tRNA to EF1 alpha releases EF1 alpha's inhibiting effect on actin polymerization. These data demonstrate that EF1 alpha can alter the assembly of F-actin, a filamentous scaffold on which non-membrane-associated protein translation may be occurring in vivo.
Collapse
Affiliation(s)
- J W Murray
- Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, New York 10461, USA
| | | | | | | |
Collapse
|
6
|
Del Priore V, Snay CA, Bahr A, Cole CN. The product of the Saccharomyces cerevisiae RSS1 gene, identified as a high-copy suppressor of the rat7-1 temperature-sensitive allele of the RAT7/NUP159 nucleoporin, is required for efficient mRNA export. Mol Biol Cell 1996; 7:1601-21. [PMID: 8898365 PMCID: PMC276009 DOI: 10.1091/mbc.7.10.1601] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
RAT7/NUP159 was identified previously in a screen for genes whose products are important for nucleocytoplasmic export of poly(A)+ RNA and encodes an essential nucleoporin. We report here the identification of RSS1 (Rat Seven Suppressor) as a high-copy extragenic suppressor of the rat7-1 temperature-sensitive allele. Rss1p encodes a novel essential protein of 538 amino acids, which contains an extended predicted coiled-coil domain and is located both at nuclear pore complexes (NPCs) and in the cytoplasm. RSS1 is the first reported high-copy extragenic suppressor of a mutant nucleoporin. Overexpression of Rss1p partially suppresses the defects in nucleocytoplasmic export of poly(A)+ RNA, rRNA synthesis and processing, and nucleolar morphology seen in rat7-1 cells shifted to the nonpermissive temperature of 37 degrees C and, thus, restores these processes to levels adequate for growth at a rate approximately one-half that of wild-type cells. After a shift to 37 degrees C, the mutant Rat7-1p/Nup159-1p is lost from the nuclear rim of rat7-1 cells and NPCs, which are clustered together in these cells grown under permissive conditions become substantially less clustered. Overexpression of Rss1p did not result in retention of the mutant Rat7-1p/Nup159-1p in NPCs, but it did result in partial maintenance of the NPC-clustering phenotype seen in mutant cells. Depletion of Rss1p by placing the RSS1 open reading frame (ORF) under control of the GAL1 promoter led to cessation of growth and nuclear accumulation of poly(A)+ RNA without affecting nuclear protein import or nuclear pore complex distribution, suggesting that RSS1 is directly involved in mRNA export. Because both rat7-1 cells and cells depleted for Rss1p are defective in mRNA export, our data are consistent with both gene products playing essential roles in the process of mRNA export and suggest that Rss1p overexpression suppresses the growth defect of rat7-1 cells at 37 degrees C by acting to maintain mRNA export.
Collapse
Affiliation(s)
- V Del Priore
- Department of Biochemistry, Dartmouth Medical School, Hanover, New Hampshire 03755, USA
| | | | | | | |
Collapse
|
7
|
Agutter PS. Intracellular structure and nucleocytoplasmic transport. INTERNATIONAL REVIEW OF CYTOLOGY 1996; 162B:183-224. [PMID: 8557487 DOI: 10.1016/s0074-7696(08)62617-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Intracellular movement of any solute or particle accords with one of two general schemes: either it takes place predominantly in the solution phase or it occurs by dynamic interactions with solid-state structures. If nucleocytoplasmic exchanges of macromolecules and complexes are predominantly solution-phase processes, i.e., if the former ("diffusionist") perspective applies, then the only significant structures in nucleocytoplasmic transport are the pore complexes. However, if such exchanges accord with the latter ("solid-state") perspective, then the roles of the nucleoskeleton and cytoskeleton in nucleocytoplasmic transport are potentially, at least, as important as that of the pore complexes. The role of the nucleoskeleton in mRNA transport is more difficult to evaluate than that of the cytoskeleton because it is less well characterized, and current evidence does not exclude either perspective. However, the balance of evidence favors a solid-state scheme. It is argued that ribosomal subunits are also more likely to migrate by a solid-state rather than a diffusionist mechanism, though the opposite is true of proteins and tRNAs. Moreover, recent data on the effects of viral proteins on intranuclear RNA processing and migration accord with the solid-state perspective. In view of this balance of evidence, three possible solid-state mechanisms for nucleocytoplasmic mRNA transport are described and evaluated. The explanatory advantage of solid-state models is contrasted with the heuristic advantage of diffusion theory, but it is argued that diffusion theory itself, even aided by modern computational techniques and numerical and graphical approaches, cannot account for data describing the movements of materials within the cell. Therefore, the mechanisms envisaged in a diffusionist perspective cannot be confined to diffusion alone, but must include other processes such as bulk fluid flow.
Collapse
Affiliation(s)
- P S Agutter
- Department of Biological Sciences, Napier University, Edinburgh, Scotland, United Kingdom
| |
Collapse
|
8
|
van Driel R, Wansink DG, van Steensel B, Grande MA, Schul W, de Jong L. Nuclear domains and the nuclear matrix. INTERNATIONAL REVIEW OF CYTOLOGY 1996; 162A:151-89. [PMID: 8575880 DOI: 10.1016/s0074-7696(08)61231-0] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
This overview describes the spatial distribution of several enzymatic machineries and functions in the interphase nucleus. Three general observations can be made. First, many components of the different nuclear machineries are distributed in the nucleus in a characteristic way for each component. They are often found concentrated in specific domains. Second, nuclear machineries for the synthesis and processing of RNA and DNA are associated with an insoluble nuclear structure, called nuclear matrix. Evidently, handling of DNA and RNA is done by immobilized enzyme systems. Finally, the nucleus seems to be divided in two major compartments. One is occupied by compact chromosomes, the other compartment is the space between the chromosomes. In the latter, transcription takes place at the surface of chromosomal domains and it houses the splicing machinery. The relevance of nuclear organization for efficient gene expression is discussed.
Collapse
Affiliation(s)
- R van Driel
- E. C. Slater Instituut, University of Amsterdam, The Netherlands
| | | | | | | | | | | |
Collapse
|
9
|
Litman P, Barg J, Ginzburg I. Microtubules are involved in the localization of tau mRNA in primary neuronal cell cultures. Neuron 1994; 13:1463-74. [PMID: 7993638 DOI: 10.1016/0896-6273(94)90432-4] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Subcellular localization of neuronal mRNAs contributes to the development of identifiable microdomains. In differentiated neurons, tau mRNA is localized in the cell body and the proximal portion of the axon, and MAP2 mRNA is localized in the cell body and dendrites, whereas tubulin mRNA is restricted to the cell body. To investigate the mechanism(s) leading to segregation of mictrotubule-associated protein mRNA, we examined the role of the cytoskeleton in this process. Detergent extraction of primary neuronal cells in culture followed by in situ hybridization analysis demonstrated that tau mRNA remains bound to cytoskeleton of the treated cells. In addition, biochemical fractionation showed that tau and MAP2 mRNAs are preferentially associated with the fraction of assembled microtubules. In contrast, mRNAs restricted to the neuronal cell body, such as those of tubulin, the 68 kDa neurofilament, and mouse GAPDH, are preferentially found in the supernatant. Using cytoskeletal inhibitors, we demonstrate that tau mRNA is associated with the microtubule system, and not with the actin filaments, thus supporting the hypothesis that the mechanism of mRNA localization is a multistep pathway in which the microtubules play a crucial role.
Collapse
Affiliation(s)
- P Litman
- Department of Neurobiology, Weizmann Institute of Science, Rehovot, Israel
| | | | | |
Collapse
|
10
|
Scherrer K, Bey F. The prosomes (multicatalytic proteinases; proteasomes) and their relationship to the untranslated messenger ribonucleoproteins, the cytoskeleton, and cell differentiation. PROGRESS IN NUCLEIC ACID RESEARCH AND MOLECULAR BIOLOGY 1994; 49:1-64. [PMID: 7863004 DOI: 10.1016/s0079-6603(08)60047-1] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- K Scherrer
- Institute Jacques Monod CNRS, Paris, France
| | | |
Collapse
|
11
|
Sharpless K, Biegel D, Yang T, Pachter JS. Beta-actin mRNA-binding proteins associated with the cytoskeletal framework. EUROPEAN JOURNAL OF BIOCHEMISTRY 1993; 212:217-25. [PMID: 8444157 DOI: 10.1111/j.1432-1033.1993.tb17653.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Association of mRNA with the cytoskeletal framework (CSK) is thought to play a strategic role in the placement of mRNA in the cytoplasm. However, the molecular determinants underlying mRNA/CSK association are completely unknown. To begin addressing this issue, we have employed a binding assay to identify proteins of the CSK compartment of NIH 3T3 cells that bind in-vitro-transcribed 32P-labelled beta-actin mRNA with high affinity. Three proteins, of approximate molecular masses 27, 50 and 97 kDa, were observed to exhibit strong binding. Binding to these proteins took place at physiological salt concentration and withstood washing in 0.5 M salt. Furthermore, binding was unaffected by heparin but was inhibited by unlabelled beta-actin mRNA. Treatment of isolated CSKs with the microfilament-severing agent DNase I abolished all beta-actin mRNA-binding activities, thus suggesting a possible association of beta-actin mRNA with the microfilament network in situ. Removal of the 3' untranslated region (UTR) significantly reduced beta-actin mRNA binding to all three CSK proteins but removal of the 5' UTR mainly affected binding to the 97-kDa species and that to a lesser extent. beta-Tubulin mRNA bound to the same three CSK proteins as did beta-actin mRNA, but with considerably less avidity. In contrast, vimentin mRNA strongly recognized these CSK proteins, and further bound to a group of smaller proteins (< 29 kDa). As beta-actin mRNA, beta-tubulin mRNA and vimentin mRNA have been observed to occupy separate cytoplasmic locales, the proteins detected here may be operative both in binding mRNAs to the CSK in situ, as well as in localizing mRNA in the cytoplasm.
Collapse
Affiliation(s)
- K Sharpless
- Department of Physiology, University of Connecticut Health Center, Farmington
| | | | | | | |
Collapse
|
12
|
Joachims M, Etchison D. Poliovirus infection results in structural alteration of a microtubule-associated protein. J Virol 1992; 66:5797-804. [PMID: 1326643 PMCID: PMC241455 DOI: 10.1128/jvi.66.10.5797-5804.1992] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Poliovirus infection results in profound changes in cellular metabolism and architecture. To identify alterations in cellular proteins following poliovirus infection which might account for these changes, monoclonal antibodies were prepared by screening for differences in antigen pattern in infected and uninfected cell lysates. Further characterization of the antigen of one such antibody (25 C C1) is described in this report. The 25 C C1 antigen is a cytoskeleton-associated protein which decreases in size 4 to 5 h postinfection. It copurifies with some of the protein synthesis initiation factors but not with eucaryotic initiation factor (eIF)-4F, the p220 subunit of which is cleaved following infection (D. Etchison, S. C. Milburn, I. Edery, N. Sonenberg, and J. W. B. Hershey, J. Biol. Chem. 257:14806-14810, 1982). Unlike alteration of p220, alteration of the 25 C C1 antigen is not due to a protease which can be detected by cell lysate mixing experiments. Alteration of the antigen occurs during purification, suggesting progressive proteolysis, but the alteration is more extensive in preparations from infected cells than in those from uninfected cells. A recombinant phage expressing the antigenic determinant was isolated from a human fibroblast cDNA library, and the sequence of the cDNA insert was found to be entirely contained within the established sequence of microtubule-associated protein (MAP) 4 (R. R. West, K. M. Tenbarge, and J. B. Olmsted, J. Biol. Chem. 266:21886-21896, 1991). The antigen distribution, as detected by indirect immunofluorescence, was similar to, but more diffuse than, the distribution of tubulin. The antibody recognized the largest abundant HeLa cell MAP, which copurified with tubulin after three cycles of polymerization-depolymerization, thus confirming the identity of the antigen as MAP 4. These results indicate that poliovirus infection of HeLa cells affects the structural integrity of a cytoskeletal protein, MAP 4.
Collapse
Affiliation(s)
- M Joachims
- Department of Microbiology, Molecular Genetics and Immunology, University of Kansas Medical Center, Kansas City 66160
| | | |
Collapse
|
13
|
Abstract
The localization of mRNA appears to facilitate protein sorting, so that proteins are synthesized in specific cellular regions. The spatial information on the mRNA may be transduced by proteins that recognize specific localizing sequences on the 3' end and then chaperone the mRNA, presumably along filaments, to its destination. Additional sequences such as poly(A), or the nascent chains of cytoskeleton-associated proteins, may then anchor mRNAs on the cytoskeleton.
Collapse
Affiliation(s)
- R H Singer
- Department of Cell Biology, University of Massachusetts, Worcester 01655
| |
Collapse
|
14
|
Biegel D, Pachter JS. mRNA association with the cytoskeletal framework likely represents a physiological binding event. J Cell Biochem 1992; 48:98-106. [PMID: 1583074 DOI: 10.1002/jcb.240480114] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
A multitude of studies has indicated that the vast majority of mRNA and polyribosomes is associated with the detergent-resistant cytoskeletal framework (CSK). However, the nature and purpose of this association remain unclear. To begin unraveling the factors which may mediate this phenomenon, we examined the extent of association of four mRNAs (tubulin, vimentin, actin, and histone mRNA) with the CSKs of NIH 3T3 cells over a wide range of salt concentrations. Results indicate that the vast majority (greater than 90%) of each of these mRNAs remains associated with the CSK after detergent extraction of cells in low ionic strength buffer (25 mM NaCl). This association is manifest under conditions that cause the complete depolymerization of microtubules but that leave microfilaments and intermediate filaments intact. Even after extensive washing in buffer of approximately physiological ionic strength (150 mM NaCl), 75-85% of these mRNAs still remain associated with the CSK. However, at least 50% of each of these mRNAs can be eluted from the CSK by washing with buffer containing 250 mM NaCl. Not all the mRNAs, though, display the same elution profile. This suggests that different binding sites and/or different binding affinities may exist for different mRNAs. Surprisingly, close to 50% of the polyribosome population remains bound to the CSK despite washing in as much as 1.0 M NaCl. These adherent polyribosomes appear to be of the same size as those that are eluted, allaying the possibility that they are retained by the CSK simply due to size exclusion. Collectively, these data strongly imply that mRNAs are neither weakly adsorbed to the CSK nor physically trapped within the meshwork of cytoskeletal filaments.(ABSTRACT TRUNCATED AT 250 WORDS)
Collapse
Affiliation(s)
- D Biegel
- Department of Physiology, University of Connecticut Health Center, Farmington 06030
| | | |
Collapse
|