Differential Regulation of Drosha and Dicer Homologues by Stress in Tetrahymena thermophila

Tetrahymena thermophila are free-living ciliated protozoans that possess two nuclei; a diploid micronucleus used only for mating, and a polyploid macronucleus which governs gene regulation and cellular homeostasis. When environmental conditions are favorable, the micronucleus exists as heterochromatin and the macronucleus is active. However, when conditions are unfavorable, Tetrahymena will attempt to conjugate with another mating type of the same species, in order to obtain new genetic information. During conjugation, the old macronucleus breaks down and a new polyploid macronucleus is regenerated. Macronuclear breakdown in Tetrahymena is governed by small RNAs, similar to miRNAs in multicellular eukaryotes. Our previous research, using the Tetrahymena Genome Database, along with the findings of other scientists, indicates that Tetrahymena possess a number of enzymes homologous to the miRNA processing enzymes, Drosha and Dicer. In our current study, we immunolocalized these enzymes in the presence and absence of cellular stress. Our immunofluorescence data indicate that Dicer-like proteins were expressed at a higher level in stressed cells than in our control cells, while Drosha-like proteins remained at the same level in both cell types