| dc.description.abstract |
<p>The goal of this research is to identify the trafficking patterns that direct ribosomes
to the endoplasmic reticulum (ER). It is widely believed that the SRP pathway is the
only mechanism that cells use to localize mRNA and ribosomes to the ER, but this has
been found not to be a sufficient explanation for the patterns of RNA localization
in cells, namely that non-signal sequence-containing mRNA are translated on the ER
and that ribosomes retain their membrane association after translation termination.
First, a summary of the history of the field is presented to provide context for the
key, unanswered questions in the field. Then, experiments employing [32Pi] pulse-chase
labeling of HeLa cells over a time course to follow nascent ribosome trafficking are
presented. The purpose of the cell labeling was to track rRNA processing and assembly
into nascent ribosomes, followed by their export into the cytoplasm and recruitment
into active polysomes. A detergent-based cell fractionation procedure was also utilized
to separate the cytosol and ER compartments in order to observe ribosomes on their
path as they exit the nucleus and either localize to the ER or cytosolic cellular
compartment. Through this method, it was seen that ribosomes appear in both compartments
at the same time, suggesting a mechanism may be occurring in addition to SRP-dependent
ribosome trafficking. This research provides an understanding toward a mechanism that
is not currently known, but will one day more fully explain the patterns of ribosomal
localization.</p>
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