Advisory Committee Chair
David Bedwell
Advisory Committee Members
Asim Bej
Kim Keeling
Document Type
Thesis
Date of Award
2007
Degree Name by School
Master of Science (MS) College of Arts and Sciences
Abstract
In eukaryotes, translation termination is a process which is initiated by the presence of a stop codon in the A site of the ribosome and mediated by the binding of a release factor (eRF1). In most eukaryotes, any one of three stop codons UGA, UAG, or UAA, is required for the binding of eRF1. However some organisms, such as the ciliates, have diverged from this universal coding. In one type of ciliate species, Tetrahymena thermophila, UAA and UAG are no longer recognized as stop codons and now both encode a glutamine residue. It was previously thought that domain 1 of eRF1 is solely responsible for the stop codon specificity in eukaryotes. Through fusion of Tetrahymena domain 1 to domains 2 and 3 of the yeast Saccharomyces cerevisiae (Tt1/Sc23), it was shown that Tetrahymena’s domain 1 recognized all three stops when expressed in yeast cells. This suggests that other domains of Tetrahymena eRF1 may be involved in restricting stop codon recognition. In order to determine what region of Tetrahymena’s eRF1 is linked to their altered recognition, new fusion proteins were made with increasing amounts of Tetrahymena eRF1. The results of a fusion protein with domains 1 and 2 or domain 3 from Tetrahymena (Tt12/Sc3 or Sc12/Tt3, respectively) indicate that domains 2 and 3 each reduced the ability of domains 1 to recognize UAG and UAA. The complete Tetrahymena eRF1 was unable to support growth in an eRF1 knockout strain. Analysis in the presence of the second Tetrahymena release factor, eRF3 which has a ii GTPase domain required for the proper function of the intact Tetrahymena eRF1, also did not restore function of Tetrahymena eRF1, suggesting that the full length eRF1 from this organism may not interact properly with yeast ribosomes.
Recommended Citation
Heath, Cara Hope, "Determinants That Confer Stop Codon Specificity To Tetrahymena Thermophila Erf1" (2007). All ETDs from UAB. 3586.
https://digitalcommons.library.uab.edu/etd-collection/3586