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Biosynthesis and utilization of extensively undermethylated poly(A)+ RNA in CHO cells during a cycloleucine treatment
Abstract:
The role of RNA methylations in the control of mRNA maturation and incorporation into polysomes has been investigated through a study of the effects in vivo of cycloleucine, a specific inhibitor of S-adenosyl-methionine mediated methylation. During the cycloleucine treatment, the rate of biosynthesis of hnRNA and its subsequent polyadenylation were only slightly reduced as compared with untreated cells. However a significant lag-time in the cytoplasmic appearance of poly(A)+ undermethylated molecules was observed, in parallel with a transient shift in the average size of hnRNA towards higher molecular weight. Nevertheless, the total amount of pulse-labelled poly(A)+ mRNA transferred to cytoplasm after a long chase time (3 h.) was approximately the same for both cycloleucine-treated and control cells. Extensively undermethylated poly(A)+ cytoplasmic RNAs, possessing a 5' terminal cap were incorporated into polysomes in proportions very similar to control messenger molecules. These results suggest that a normal level of methylation is not stringently required for the production of the functional mRNA molecules although it appears to be of importance for the kinetics of the maturational process.
Insights
RNA methylation is not essential for producing functional messenger RNA (mRNA). However, it plays a role in the speed of mRNA maturation and its transfer to the cytoplasm.
Area of Science:
- Molecular Biology
- Epigenetics
- RNA Biology
Background:
- RNA methylation, specifically S-adenosyl-methionine mediated methylation, is crucial for various RNA processing events.
- Understanding the precise role of methylation in mRNA maturation and translation is vital for comprehending gene expression regulation.
Purpose of the Study:
- To investigate the role of RNA methylation in mRNA maturation and polysome incorporation.
- To examine the effects of cycloleucine, an inhibitor of methylation, on these processes in vivo.
Main Methods:
- In vivo study using cycloleucine to inhibit S-adenosyl-methionine mediated methylation.
- Analysis of hnRNA biosynthesis, polyadenylation, and cytoplasmic appearance of poly(A)+ RNA.
- Assessment of mRNA incorporation into polysomes.
Main Results:
- Cycloleucine treatment caused slight reductions in hnRNA biosynthesis and polyadenylation.
- A delay in cytoplasmic appearance of undermethylated poly(A)+ RNA was observed, with a transient shift in hnRNA size.
- Undermethylated mRNA molecules were incorporated into polysomes similarly to control mRNA, indicating functionality.
Conclusions:
- Normal RNA methylation levels are not strictly required for the production of functional mRNA.
- Methylation appears important for the kinetics and efficiency of the mRNA maturation process.