| Autor: |
Fehrmann, Frauke, Welker, Reinhold, Kräusslich, Hans-Georg |
| Zdroj: |
Virology; September 1997, Vol. 235 Issue: 2 p352-359, 8p |
| Abstrakt: |
Intracisternal A-type particles (IAP) are defective endogenous retroviruses that accumulate in the endoplasmic reticulum of rodent cells. IAP genomes share extensive sequence homologies with D-type retroviruses, but were presumed to express the viral proteinase (PR) as part of thegagopen reading frame (ORF) while D-type retroviruses express PR in a separate ORF. Here we show that expression of the murine IAP element MIA14 yields three major translation products, corresponding to the Gag, Gag-PR, and Gag-PR-Pol polyproteins. Sequence analysis revealed that MIA14 PR is encoded in its own reading frame, separate fromgagandpol.Frameshifting occurred with an efficiency of approximately 25% between thegagandproORFs and 35% betweenproandpol.The region containing the putativegag-proframeshift signal consists of a heptanucleotide slippery sequence (A6C) and a stem–loop structure probably forming a pseudoknot. Deletion of this structure element almost completely abolished frameshifting. Insertion of an additional base next to the frameshift signal placedgagandproin the same ORF and resulted in predominant formation of Gag-PR and Gag-PR-Pol polyproteins which were not processed followingin vitrotranslation. Expression of a similar construct in tissue culture cells, on the other hand, led to efficient intracellular processing of the mutant polyproteins. |
| Databáze: |
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