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Physical aspects and cytoplasmic distribution of messenger RNA in mouse kidney
Abstract:
As a prerequisite to examining mRNA metabolism in compensatory renal hypertrophy, polyadenylated RNA has been purified from normal mouse kidney polysomal RNA by selection on oligo(dT)-cellulose. Poly(A)-containing RNA dissociated from polysomes by treatment with 10 mM EDTA and sedimented heterogeneously in dodecyl sulfate-containing sucrose density gradients with a mean sedimentation coefficient of 20 S. Poly(A) derived from this RNA migrated at the rate of 6-7 S RNA in dodecyl sulfate-containing 10% polyacrylamide gels. Coelectrophoresis of poly(A) labeled for 90 min with poly(A) labeled for 24 h indicated the long-term labeled poly(A) migrated faster than pulse-labeled material. Twenty percent of the cytoplasmic poly(A)-containing mRNA was not associated with the polysomes, but sedimented in the 40-80 S region (post-polysomal). Messenger RNA from the post-polysomal region had sedimentation properties similar to those of mRNA prepared from polysomes indicating post-polysomal mRNA was not degraded polysomal mRNA. Preliminary labeling experiments indicated a rapid equilibration of radioactivity between the polysomal and post-polysomal mRNA populations, suggesting the post-polysomal mRNA may consist of mRNA in transit to the polysomes.
Insights
Researchers purified polyadenylated RNA from mouse kidneys to study mRNA metabolism. They found that a significant portion of mRNA exists outside of polysomes, potentially in transit to active protein synthesis.
Area of Science:
- Molecular Biology
- Biochemistry
- Genetics
Background:
- Understanding mRNA metabolism is crucial for studying cellular processes like compensatory renal hypertrophy.
- Polyadenylated RNA plays a key role in mRNA stability and translation.
Purpose of the Study:
- To purify and characterize polyadenylated RNA from normal mouse kidney polysomes.
- To investigate the distribution and properties of messenger RNA (mRNA) in cytoplasmic fractions.
Main Methods:
- Oligo(dT)-cellulose chromatography was used to isolate polyadenylated RNA from polysomal RNA.
- Sucrose density gradient centrifugation and polyacrylamide gel electrophoresis were employed to analyze RNA sedimentation and migration.
- Radioactive labeling experiments were conducted to assess mRNA turnover and localization.
Main Results:
- Polyadenylated RNA from mouse kidney polysomes was successfully purified, exhibiting a heterogeneous sedimentation profile (mean 20 S).
- The poly(A) tail derived from this mRNA migrated as 6-7 S RNA.
- A substantial fraction (20%) of cytoplasmic poly(A)-containing mRNA was found in the post-polysomal fraction, with properties similar to polysomal mRNA.
- Labeling experiments suggested rapid exchange between polysomal and post-polysomal mRNA pools, indicating the latter may be in transit.
Conclusions:
- The study successfully isolated and characterized polyadenylated mRNA from mouse kidney polysomes.
- A significant non-polysomal pool of mRNA exists, likely representing mRNA actively moving towards or from polysomes.
- These findings provide a foundation for further investigation into mRNA metabolism during compensatory renal hypertrophy.