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Isolation and Expression of Two Genes Encoding Eukaryotic Release Factor 1 from Paramecium tetraurelia
Author(s) -
KERVESTIN STEPHANIE,
GARNIER OLIVIER A.,
KARAMYSHEV ANDREY L.,
ITO KOICHI,
NAKAMURA YOSHIKAZU,
MEYER ERIC,
JEANJEAN OLIVIER
Publication year - 2002
Publication title -
journal of eukaryotic microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.067
H-Index - 77
eISSN - 1550-7408
pISSN - 1066-5234
DOI - 10.1111/j.1550-7408.2002.tb00215.x
Subject(s) - biology , release factor , stop codon , genetics , gene , genetic code , codon usage bias , paramecium , transfer rna , coding region , gene duplication , genome , microbiology and biotechnology , rna
.Paramecium tetraurelia , like some other ciliate species, uses an alternative nuclear genetic code where UAA and UAG are translated as glutamine and UGA is the only stop codon. It has been postulated that the use of stop codons as sense codons is dependent on the presence of specific tRNAs and on modification of eukaryotic release factor one (eRFl), a factor involved in stop codon recognition during translation termination. We describe here the isolation and characterisation of two genes, eRF1‐a and eRF1‐b , coding for eRFl in P. tetraurelia. The two genes are very similar, both in genomic organization and in sequence, and might result from a recent duplication event. The two coding sequences are 1,314 nucleotides long, and encode two putative proteins of 437 amino acids with 98.5% identity. Interestingly, when compared with the eRFl sequences either of ciliates having the same variant genetic code, or of other eukaryotes, the eRFl of P. tetraurelia exhibits significant differences in the N‐terminal region, which is thought to interact with stop codons. We discuss here the consequences of these changes in the light of recent models proposed to explain the mechanism of stop codon recognition in eukaryotes. Besides, analysis of the expression of the two genes by Northern blotting and primer extension reveals that these genes exhibit a differential expression during vegetative growth and autogamy.