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UGA is translated as cysteine in pheromone 3 of Euplotes octocarinatus.

ABSTRACT: Pheromone 3 mRNA of the ciliate Euplotes octocarinatus contains three in-frame UGA codons that are translated as cysteines. This was revealed from cDNA sequencing and from plasma desorption mass spectrometry of cleaved pheromone 3 in connection with pyridylethylation of the fragments. N-terminal sequence analysis of carboxymethylated protein confirmed this conclusion for the first of the three UGA codons. Besides UGA the common cysteine codons UGU and UGC are also used to encode cysteine. UAA functions as a termination codon. No UAG codon was found. In connection with results reported for other ciliates, this suggests that the role of the classic termination codons had not yet been established when the ciliates started to diverge from other eukaryotes.

SUBMITTER: Meyer F

PROVIDER: S-EPMC51532 | biostudies-other | 1991 May

REPOSITORIES: biostudies-other

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UGA is translated as cysteine in pheromone 3 of Euplotes octocarinatus.

Meyer F F Schmidt H J HJ Plümper E E Hasilik A A Mersmann G G Meyer H E HE Engström A A Heckmann K K

Proceedings of the National Academy of Sciences of the United States of America 19910501 9

Pheromone 3 mRNA of the ciliate Euplotes octocarinatus contains three in-frame UGA codons that are translated as cysteines. This was revealed from cDNA sequencing and from plasma desorption mass spectrometry of cleaved pheromone 3 in connection with pyridylethylation of the fragments. N-terminal sequence analysis of carboxymethylated protein confirmed this conclusion for the first of the three UGA codons. Besides UGA the common cysteine codons UGU and UGC are also used to encode cysteine. UAA fu ...[more]

PMID: 1902568

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Project description:Like many other organisms, ciliates communicate and interact socially via diffusible chemical signals, named pheromones, that are functionally associated with a genetic mating-type mechanism of cell self/not-self recognition. In Euplotes species, pheromones form species-specific families of small, globular, and disulfide-rich proteins folding into exclusively helical secondary structures. Each is specified by one of a series of high-multiple alleles that are inherited in Mendelian fashion with relationships of co-dominance at the so-called mat genetic locus of the cell transcriptionally inert micronuclear genome, and expressed in the transcriptionally active macronuclear genome as individual DNA molecules in which the central coding region is flanked by 5'-leader and 3'-trailer noncoding regions ending with C4A4/T4G4 telomeric repeats. In E. crassus, a cosmopolitan marine species with a long tradition in the study of ciliate mating systems and breeding patterns, oligonucleotides specific to amino acid sequences of pheromones Ec-1 and Ec-α were previously used to clone and sequence a first set of four structurally distinct macronuclear (mac) pheromone coding genes, mac-ec-α, mac-ec-1, mac-ec-2 and mac-ec-3, from two interbreeding strains, L-2D and POR-73. The use of these oligonucleotides in PCR amplifications of macronuclear DNA preparations from three other E. crassus interbreeding strains, ES10, Fava4 and MN4, has now resulted in the characterization of a second set of eight new pheromone coding genes, mac-ec-β, mac-ec-γ, mac-ec-δ, mac-ec-ε, mac-ec-µ, mac-ec-4, mac-ec-5 and mac-ec-6. Multiple alignment between previously and newly determined pheromone-gene sequences reinforces the concept that the E. crassus pheromone-gene family includes two sub-families, which likely reflect a duplication of the micronuclear mat gene locus and represent an apomorphic trait of the E. crassus clade. Members of one sub-family (each identified with a Greek letter) show a 500-bp 5'-leader noncoding region rich in AGGA/AGGGA repetitions, and encode 56-amino acid pheromones with eight conserved Cys residues. Members of the other sub-family (each identified with an Arabic numeral) show an 800-bp 5'-leader noncoding region without AGGA/AGGGA repetitions, and encode 45-amino acid pheromones with ten conserved Cys residues.

Project description:BACKGROUND: There are thousands of very diverse ciliate species from which only a handful mitochondrial genomes have been studied so far. These genomes are rather similar because the ciliates analysed (Tetrahymena spp. and Paramecium aurelia) are closely related. Here we study the mitochondrial genomes of the hypotrichous ciliates Euplotes minuta and Euplotes crassus. These ciliates are only distantly related to Tetrahymena spp. and Paramecium aurelia, but more closely related to Nyctotherus ovalis, which possesses a hydrogenosomal (mitochondrial) genome. RESULTS: The linear mitochondrial genomes of the hypotrichous ciliates Euplotes minuta and Euplotes crassus were sequenced and compared with the mitochondrial genomes of several Tetrahymena species, Paramecium aurelia and the partially sequenced mitochondrial genome of the anaerobic ciliate Nyctotherus ovalis. This study reports new features such as long 5'gene extensions of several mitochondrial genes, extremely long cox1 and cox2 open reading frames and a large repeat in the middle of the linear mitochondrial genome. The repeat separates the open reading frames into two blocks, each having a single direction of transcription, from the repeat towards the ends of the chromosome. Although the Euplotes mitochondrial gene content is almost identical to that of Paramecium and Tetrahymena, the order of the genes is completely different. In contrast, the 33273 bp (excluding the repeat region) piece of the mitochondrial genome that has been sequenced in both Euplotes species exhibits no difference in gene order. Unexpectedly, many of the mitochondrial genes of E. minuta encoding ribosomal proteins possess N-terminal extensions that are similar to mitochondrial targeting signals. CONCLUSION: The mitochondrial genomes of the hypotrichous ciliates Euplotes minuta and Euplotes crassus are rather different from the previously studied genomes. Many genes are extended in size compared to mitochondrial genes from other sources.

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UGA is translated as cysteine in pheromone 3 of Euplotes octocarinatus.

Publications

UGA is translated as cysteine in pheromone 3 of Euplotes octocarinatus.

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