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Adenovirus type 2 fiber mRNA synthesis: no evidence for a cytoplasmic processing pathway
Abstract:
Adenovirus type 2 fiber mRNA exists in several forms in the cytoplasm which differ in the presence or absence of extra 5'-leader segments (L. T. Chow and T. R. Broker, Cell 15:497-510, 1978). We have investigated the possibility that forms possessing extra leader segments serve as precursors to the mature form in the cytoplasm. Pulse-labeled fiber mRNA became considerably shorter (150 to 250 bases) during a chase; however, most of the pulse-labeled species failed to hybridize to DNA fragments known to encode extra leader segments. Moreover, the entire decrease in size appeared to be due to extensive shortening of the polyadenylic acid tail. Mature-sized fiber mRNA was synthesized normally in cells infected with the nondefective adenovirus type 2-simian virus 40 hybrid virus Ad2+ND5, in which the region encoding the extra leader segments is deleted. These results indicate that the additional 5'-leader segments present in wild-type adenovirus type 2 fiber mRNA are not required for the production of mature fiber mRNA and that species that possess them are not cytoplasmic precursors to the mature form.
Insights
Adenovirus type 2 fiber messenger RNA (mRNA) with extra 5' leader segments are not cytoplasmic precursors to the mature form. These extra segments are not required for mature fiber mRNA production.
Area of Science:
- Molecular Biology
- Virology
- Gene Expression
Background:
- Adenovirus type 2 fiber messenger RNA (mRNA) exists in multiple cytoplasmic forms.
- These forms differ by the presence or absence of additional 5'-leader segments.
Purpose of the Study:
- To investigate if adenovirus type 2 fiber mRNA forms with extra 5'-leader segments act as precursors to the mature cytoplasmic form.
- To determine the role of these extra leader segments in mature mRNA production.
Main Methods:
- Pulse-labeling of fiber mRNA followed by a chase period to observe size changes.
- Hybridization of labeled mRNA to DNA fragments encoding leader segments.
- Analysis of mature-sized fiber mRNA synthesis in cells infected with a hybrid virus lacking the leader segment encoding region.
Main Results:
- Pulse-labeled fiber mRNA significantly decreased in size during the chase period.
- Most labeled species did not hybridize to DNA encoding extra leader segments.
- Size reduction was primarily due to polyadenylic acid tail shortening.
- Mature-sized fiber mRNA was synthesized normally in cells infected with a virus lacking the extra leader segment region.
Conclusions:
- The additional 5'-leader segments in wild-type adenovirus type 2 fiber mRNA are not essential for mature mRNA production.
- Cytoplasmic forms of adenovirus type 2 fiber mRNA possessing extra leader segments are not precursors to the mature form.