Sequencing of a Novel Rearrangement Site on Micronuclear Chromosome 1 of Tetrahymena thermophila
- Eileen Hamilton, Project Scientist, University of California Santa Barbara
- Eduardo Orias, Principal Investigator, University of California Santa Barbara
Tetrahymena thermophila is a unicellular eukaryote extensively used in biological research. It exhibits both sexual and asexual reproductive stages. Its genome is contained in two nuclei. The micronucleus (MIC) is the germline nucleus; it contains five pairs of chromosomes and is phenotypically silent. The macronucleus (MAC) is the somatic nucleus; it contains 181 chromosomes and it is the site of gene expression. Both genomes have been sequenced, however, the MIC genomic sequence contains many gaps. During the sexual stage, a mitotic copy of the MIC gives rise to the MAC. This process is known as macronuclear differentiation and involves programmed genome rearrangements; similar events have been observed in other eukaryotes. A newly discovered type of genome rearrangement causes MIC DNA segments that are far apart in the MIC to come together during the formation of a new MAC chromosome. The first step in investigating this mechanism is determining the sequence of the MIC segments being joined. I am confirming the sequence of a MIC chromosome 1 region that is involved in this type of genome rearrangement. I used polymerase chain reaction to amplify MIC DNA fragments, then cloned and sequenced the products. In addition to filling sequence gaps, small errors were found and corrected in the MIC genomic sequence. The complete, corrected sequence of this region will facilitate the understanding of these novel rearrangement mechanisms in eukaryotes.