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Characterization and purification of messenger RNAs containing poly A in insect imaginal disks
Abstract:
The presence of a fragment of polyA resistant to both T1 and p ribonucleases in mRNAs extracted from wing imaginal disks of an insect, Pieris brassicae, is reported. Its length was approximatively 150 nucleotides. PolyU sepharose affinity chromatography was subsequently used for purification of these polyA(+)mRNA molecules. Analyses on sucrose gradients showed a good recovery of poly(+)molecules characterized by their size (20-100 S) and a polydisperse pattern. These mRNAlike species represent 2-3 per cent of the total radioactivity incorporated into RNA in 3 hours of labeling. Sequential extractions were carried out to provide cytoplasmic RNA rich fractions (4 degrees C) and nuclear rich fractions (45 degrees C). When assayed for the presence of polyA(+)RNA, molecules extracted by these two sequential methods were found to be very similar in their polyA content.
Insights
Researchers identified a unique polyA fragment in insect mRNA, resistant to specific enzymes. This discovery sheds light on mRNA processing and stability in Pieris brassicae.
Area of Science:
- Molecular Biology
- Insect Biochemistry
- RNA Biology
Background:
- Messenger RNA (mRNA) molecules typically possess a polyadenylated tail (polyA) crucial for stability and translation.
- Ribonucleases (RNases) are enzymes that degrade RNA, playing a role in RNA metabolism.
- Wing imaginal disks are developmental structures in insects used to study gene expression and RNA processing.
Purpose of the Study:
- To investigate the characteristics of polyadenylated RNA (polyA(+)RNA) in the mRNA of Pieris brassicae.
- To identify and characterize any unusual polyA fragments resistant to enzymatic degradation.
Main Methods:
- Extraction of mRNA from Pieris brassicae wing imaginal disks.
- Purification of polyA(+)mRNA using PolyU sepharose affinity chromatography.
- Analysis of purified polyA(+)RNA size and distribution using sucrose gradient centrifugation.
- Sequential extraction of cytoplasmic and nuclear RNA fractions.
Main Results:
- A polyA fragment, approximately 150 nucleotides long, resistant to T1 and p ribonucleases, was detected in insect mRNA.
- Purified polyA(+)mRNA molecules were recovered efficiently, exhibiting sizes between 20-100 S with a polydisperse pattern.
- These polyA(+)mRNA species constituted 2-3% of total RNA radioactivity after 3 hours of labeling.
- Both cytoplasmic and nuclear RNA fractions showed similar polyA(+)RNA content.
Conclusions:
- The study reports the presence of a novel, enzyme-resistant polyA fragment in insect mRNA.
- This finding suggests unique mechanisms for mRNA processing or stability in Pieris brassicae.
- The polyA(+)RNA molecules are characterized by their size distribution and cellular localization.