Related Experiment Videos
mRNA association with the cytoskeletal framework likely represents a physiological binding event
1Department of Physiology, University of Connecticut Health Center, Farmington 06030.
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)
Insights
Most messenger RNAs (mRNAs) and polyribosomes bind to the detergent-resistant cytoskeletal framework (CSK). This association is salt-dependent, suggesting specific binding interactions rather than passive trapping within the cytoskeleton.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- The majority of mRNA and polyribosomes associate with the detergent-resistant cytoskeletal framework (CSK).
- The precise nature and function of this mRNA-cytoskeleton association are not fully understood.
Purpose of the Study:
- To investigate the salt-dependent association of specific mRNAs with the cytoskeletal framework (CSK).
- To explore the potential binding affinities and mechanisms mediating mRNA-CSK interactions.
Main Methods:
- Extraction of NIH 3T3 cells with detergent.
- Washing of cytoskeletal frameworks (CSKs) with buffers of varying salt concentrations (25 mM to 1.0 M NaCl).
- Quantification of associated mRNAs (tubulin, vimentin, actin, histone) and polyribosomes.
Main Results:
- Over 90% of tested mRNAs remained associated with the CSK in low salt (25 mM NaCl).
- 75-85% of mRNAs stayed bound at physiological salt (150 mM NaCl), with 50% eluting at 250 mM NaCl, indicating differential binding affinities.
- Approximately 50% of polyribosomes remained bound even at 1.0 M NaCl, suggesting strong interactions.
Conclusions:
- mRNA association with the CSK is robust and salt-sensitive, implying specific binding mechanisms.
- Different mRNAs may exhibit distinct binding characteristics to the CSK.
- A significant portion of polyribosomes exhibits strong adherence to the CSK, not explained by simple size exclusion.