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Ribosomal frameshifting may be controlled by mechanisms found in the mRNA sequence (cis-acting). This generally refers to a slippery sequence, an RNA secondary structure, or both. A −1 frameshift signal consists of both elements separated by a spacer region typically 5–9 nucleotides long. [ 2 ]
A slippery sequence is a small section of codon nucleotide sequences (usually UUUAAAC) that controls the rate and chance of ribosomal frameshifting. A slippery sequence causes a faster ribosomal transfer which in turn can cause the reading ribosome to "slip."
In molecular cell biology the Insertion sequence IS1222 ribosomal frameshifting element is an RNA element found in the insertion sequence IS222. The ribosomal frameshifting element stimulates frameshifting which is known to be required for transposition .
The HIV-1 ribosomal frameshift signal requires two cis-acting elements: a heptameric "slippery site" and a downstream secondary RNA structure separated by an 8-nucleotide spacer. [3] [4] The "Slippery Site" in HIV-1 is the heptamer 5'-U UUU UUA-3' (gag ORF indicated by the spaces), where frameshifting occurs.
The DnaX ribosomal frameshifting element is a RNA element found in the mRNA of the dnaX gene in E. coli. The dnaX gene has two encoded products, tau and gamma, which are produced in a 1:1 ratio. The gamma protein is synthesised due to programmed frameshifting and is shorter than tau.
Frameshifting may also occur during prophase translation, producing different proteins from overlapping open reading frames, such as the gag-pol-env retroviral proteins. This is fairly common in viruses and also occurs in bacteria and yeast (Farabaugh, 1996).
Created Date: 8/30/2012 4:52:52 PM
Translation can also be affected by ribosomal pausing, which can trigger endonucleolytic attack of the tRNA, a process termed mRNA no-go decay. Ribosomal pausing also aids co-translational folding of the nascent polypeptide on the ribosome, and delays protein translation while it is encoding tRNA. This can trigger ribosomal frameshifting. [7]