Document Type




Format of Original

10 p.

Publication Date



American Society for Microbiology

Source Publication

Eukaryotic Cell

Source ISSN


Original Item ID

doi: 10.1128/EC.3.3.685-694.2004


Three insertion elements were previously found in a family of germ line-limited mobile elements, the Tlr elements, in the ciliate Tetrahymena. Each of the insertions contains an open reading frame (ORF). Sequence analysis of the deduced proteins encoded by the elements suggests that they are homing endonucleases. The genes are designated TIE1-1, TIE2-1, and TIE3-1 for Tetrahymena insertion-homing endonuclease. The endonuclease motif occupies the amino terminal half of each TIE protein. The C-terminal regions of the proteins are similar to the APETELA2 DNA binding domain of plant transcription factors. The TIE1 and TIE3 elements belong to families of repeated sequences in the germ line micronuclear genome. Comparison of the genes and the deduced proteins they encode suggests that there are at least two distinct families of homing endonuclease genes, each of which appears to be preferentially associated with a specific region of the Tlr elements. The TIE1 and TIE3 elements and their cognates undergo programmed elimination from the developing somatic macro-nucleus of Tetrahymena. The possible role of homing endonuclease-like genes in the DNA breakage step in developmentally programmed DNA elimination in Tetrahymena is discussed.


Published version. Eukaryotic Cell, Vol. 3, No. 3 (June 2004): 685-694. DOI. © 2004 American Society for Microbiology. Used with permission.

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