Logo of pnasPNASInfo for AuthorsSubscriptionsAboutThis Article
Proc Natl Acad Sci U S A. 1985 Apr; 82(8): 2452–2455.
PMCID: PMC397576

An unusual genetic code in nuclear genes of Tetrahymena.


We have cloned and partially sequenced two histone H3 genes of Tetrahymena thermophila. The DNA sequences strongly suggest that both genes are active in the vegetatively growing cell. Comparison of the derived amino acid sequences of these two genes with the actual sequence of Tetrahymena histone H3 results in the surprising conclusion that TAA codes for glutamine. This represents the first demonstration of a coding function for this termination codon of the "universal" code. This observation has important implications for the evolution of ciliates and of the genetic code.

Full text

Full text is available as a scanned copy of the original print version. Get a printable copy (PDF file) of the complete article (751K), or click on a page image below to browse page by page. Links to PubMed are also available for Selected References.

Selected References

These references are in PubMed. This may not be the complete list of references from this article.
  • Grivell LA. Mitochondrial DNA. Sci Am. 1983 Mar;248(3):78–89. [PubMed]
  • Mahler HR. Mitochondrial evolution: organization and regulation of mitochondrial genes. Ann N Y Acad Sci. 1981;361:53–75. [PubMed]
  • Mahler HR. The exon:intron structure of some mitochondrial genes and its relation to mitochondrial evolution. Int Rev Cytol. 1983;82:1–98. [PubMed]
  • Jukes TH. Evolution of the amino acid code: inferences from mitochondrial codes. J Mol Evol. 1983;19(3-4):219–225. [PubMed]
  • Jukes TH. Mitochondrial codes and evolution. Nature. 1983 Jan 6;301(5895):19–20. [PubMed]
  • Gorovsky MA, Yao MC, Keevert JB, Pleger GL. Isolation of micro- and macronuclei of Tetrahymena pyriformis. Methods Cell Biol. 1975;9(0):311–327. [PubMed]
  • Bannon GA, Calzone FJ, Bowen JK, Allis CD, Gorovsky MA. Multiple, independently regulated, polyadenylated messages for histone H3 and H4 in Tetrahymena. Nucleic Acids Res. 1983 Jun 25;11(12):3903–3917. [PMC free article] [PubMed]
  • Leder P, Tiemeier D, Enquist L. EK2 derivatives of bacteriophage lambda useful in the cloning of DNA from higher organisms: the lambdagtWES system. Science. 1977 Apr 8;196(4286):175–177. [PubMed]
  • Benton WD, Davis RW. Screening lambdagt recombinant clones by hybridization to single plaques in situ. Science. 1977 Apr 8;196(4286):180–182. [PubMed]
  • Bannon GA, Bowen JK, Yao MC, Gorovsky MA. Tetrahymena H4 genes: structure, evolution and organization in macro- and micronuclei. Nucleic Acids Res. 1984 Feb 24;12(4):1961–1975. [PMC free article] [PubMed]
  • Smith MM, Murray K. Yeast H3 and H4 histone messenger RNAs are transcribed from two non-allelic gene sets. J Mol Biol. 1983 Sep 25;169(3):641–661. [PubMed]
  • Southern EM. Detection of specific sequences among DNA fragments separated by gel electrophoresis. J Mol Biol. 1975 Nov 5;98(3):503–517. [PubMed]
  • Pustell J, Kafatos FC. A convenient and adaptable package of computer programs for DNA and protein sequence management, analysis and homology determination. Nucleic Acids Res. 1984 Jan 11;12(1 Pt 2):643–655. [PMC free article] [PubMed]
  • Hayashi T, Hayashi H, Fusauchi Y, Iwai K. Tetrahymena histone H3. Purification and two variant sequences. J Biochem. 1984 Jun;95(6):1741–1749. [PubMed]
  • Nagylaki T, Petes TD. Intrachromosomal gene conversion and the maintenance of sequence homogeneity among repeated genes. Genetics. 1982 Feb;100(2):315–337. [PMC free article] [PubMed]
  • Kaine BP, Spear BB. Nucleotide sequence of a macronuclear gene for actin in Oxytricha fallax. Nature. 1982 Feb 4;295(5848):430–432. [PubMed]
  • Woese CR. On the evolution of the genetic code. Proc Natl Acad Sci U S A. 1965 Dec;54(6):1546–1552. [PMC free article] [PubMed]
  • Tarr GE, Fitch WM. Amino acid sequence of cytochrome c from Tetrahymena pyriformis Phenoset A. Biochem J. 1976 Nov;159(2):193–199. [PMC free article] [PubMed]
  • Glover CV, Gorovsky MA. Amino-acid sequence of Tetrahymena histone H4 differs from that of higher eukaryotes. Proc Natl Acad Sci U S A. 1979 Feb;76(2):585–589. [PMC free article] [PubMed]
  • Fusauchi Y, Iwai K. Tetrahymena histone H2A. Isolation and two variant sequences. J Biochem. 1983 Jun;93(6):1487–1497. [PubMed]
  • Vaughn JC, Sperbeck SJ, Ramsey WJ, Lawrence CB. A universal model for the secondary structure of 5.8S ribosomal RNA molecules, their contact sites with 28S ribosomal RNAs, and their prokaryotic equivalent. Nucleic Acids Res. 1984 Oct 11;12(19):7479–7502. [PMC free article] [PubMed]
  • Kuchino Y, Mita T, Nishimura S. Nucleotide sequence of cytoplasmic initiator tRNA from Tetrahymena thermophila. Nucleic Acids Res. 1981 Sep 25;9(18):4557–4562. [PMC free article] [PubMed]
  • Helftenbein E. Nucleotide sequence of a macronuclear DNA molecule coding for alpha-tubulin from the ciliate Stylonychia lemnae. Special codon usage: TAA is not a translation termination codon. Nucleic Acids Res. 1985 Jan 25;13(2):415–433. [PMC free article] [PubMed]

Articles from Proceedings of the National Academy of Sciences of the United States of America are provided here courtesy of National Academy of Sciences


Save items

Related citations in PubMed

See reviews...See all...

Cited by other articles in PMC

See all...


  • Compound
    PubChem Compound links
  • Gene (nucleotide)
    Gene (nucleotide)
    Records in Gene identified from shared sequence links
  • MedGen
    Related information in MedGen
  • Nucleotide
    Published Nucleotide sequences
  • Protein
    Published protein sequences
  • PubMed
    PubMed citations for these articles
  • Substance
    PubChem Substance links

Recent Activity

Your browsing activity is empty.

Activity recording is turned off.

Turn recording back on

See more...