All ETDs from UAB

Advisory Committee Chair

David Bedwell

Advisory Committee Members

Asim Bej

Kim Keeling

Document Type


Date of Award


Degree Name by School

Master of Science (MS) College of Arts and Sciences


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.



To view the content in your browser, please download Adobe Reader or, alternately,
you may Download the file to your hard drive.

NOTE: The latest versions of Adobe Reader do not support viewing PDF files within Firefox on Mac OS and if you are using a modern (Intel) Mac, there is no official plugin for viewing PDF files within the browser window.