This chapter discusses the DNA–protein complexes found at telomeres in the macronuclei of ciliated protozoans, with special attention given to studies in Oxytricha (a hypotrichous ciliate) and Tetrahymena (a holotrichous ciliate). The structure of telomeres has been largely elucidated by studies on macronuclear DNA from ciliated protozoans. Studies of Tetrahymena recombinant DNA (rDNA) termini provided the first telomeric DNA sequence. Short tandem repeats, very similar to those described in Tetrahymena, have since been detected at telomeres in a wide variety of lower eukaryotes. The Tetrahymena rDNA termini also provided the first indication that telomeres exist in a non-nucleosomal DNA–protein complex. Subsequent studies from Oxytricha macronuclei have generated further insights into telomere structure. The terminal ∼135 bp of Oxytricha macronuclear DNA molecules are packaged in a non-nucleosomal protein complex. Internal to the non-nucleosomal telomeric complex are several precisely positioned nucleosomes, a phenomenon that has been observed on the extrachromosomal rDNA molecules from Tetrahymena and Dictyostelium.
All Science Journal Classification (ASJC) codes
- Molecular Biology
- Cell Biology