Open AccessDistinct Paths To Stop Codon Reassignment by the Variant-Code Organisms Tetrahymena and Euplotes
Author(s) -
Joe Salas-Marco,
Hua Fan-Minogue,
Adam K. Kallmeyer,
Lawrence A. Klobutcher,
Philip J. Farabaugh,
David M. Bedwell
Publication year - 2006
Publication title -
molecular and cellular biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.14
H-Index - 327
eISSN - 1067-8824
pISSN - 0270-7306
DOI - 10.1128/mcb.26.2.438-447.2006
Subject(s) - tetrahymena , release factor , stop codon , biology , genetics , ciliate , saccharomyces cerevisiae , codon usage bias , genetic code , translation (biology) , start codon , gene , transfer rna , messenger rna , genome , rna
The reassignment of stop codons is common among many ciliate species. For example,Tetrahymena species recognize only UGA as a stop codon, whileEuplotes species recognize only UAA and UAG as stop codons. Recent studies have shown that domain 1 of the translation termination factor eRF1 mediates stop codon recognition. While it is commonly assumed that changes in domain 1 of ciliate eRF1s are responsible for altered stop codon recognition, this has never been demonstrated in vivo. To carry out such an analysis, we made hybrid proteins that contained eRF1 domain 1 from eitherTetrahymena thermophila orEuplotes octocarinatus fused to eRF1 domains 2 and 3 fromSaccharomyces cerevisiae . We found that theTetrahymena hybrid eRF1 efficiently terminated at all three stop codons when expressed in yeast cells, indicating that domain 1 is not the sole determinant of stop codon recognition inTetrahymena species. In contrast, theEuplotes hybrid facilitated efficient translation termination at UAA and UAG codons but not at the UGA codon. Together, these results indicate that while domain 1 facilitates stop codon recognition, other factors can influence this process. Our findings also indicate that these two ciliate species used distinct approaches to diverge from the universal genetic code.