The Study of in vivo -1 Ribosomal Frameshifting Efficiency
Date Issued
2011
Date
2011
Author(s)
Chung, Te-Pao
Abstract
Two subunits (tau and gamma) of the DNA polymerase III holoenzyme in Escherichia coli are produced through efficient -1 programmed ribosomal frameshifting. The efficiency of frameshifting is determined by the elements around the shift site on mRNA, including the slippery sequence, secondary structure and the distance between them. In general, increasing the translation initiation frequency will shorten the space between neighboring ribosomes on the mRNA and then increase the possibility of polysome formation. As a result, once the secondary structure is unfolded by a preceding ribosome, it may remain open until the next ribosome reaches. Thus, the frameshifting efficiency may be decreased.
In this study, we use the dnaX frameshifting motif as a model system to explore the relationship between polysome and frameshifting efficiency. Our results suggest that a downstream ribosome unfolds the secondary structure of the mRNA and blocks refolding when it is terminated on the stop codon just after the secondary structure. In the meantime, an upstream ribosome coming to the frameshifting site encounters no secondary structures. Thus, fewer ribosomes are induced to undergo -1 frameshifting. The frameshifting efficiency will be restored while the formation frequency of polysome decreases. Our results support that frameshifting efficiency may be affected not only by the sequence itself, but also by the interaction between ribosomes on the mRNA.
Subjects
translation
frameshifting
polysome
ribosome
Type
thesis
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