Project description:Microarray analyses were performed to compare the gene expression profiles of wild-type and several mutant strains of the ciliated protozoan Tetrahymena thermophila. Elimination of H3K4 methylation (hht2-K4Q) and knockout of either of the ubiquitylation enzymes (delta-UBC2 and delta-BRE1) affects a broader spectrum of genes than elimination of H2B ubiquitylation (htb1-K115R). Cells at mid-logarithmic growing phase (cell density of 200,000 cells/ml) were collected. Then total RNAs were extracted and hybridized.
Project description:Microarray analyses were performed to compare the gene expression profiles of wild-type and several mutant strains of the ciliated protozoan Tetrahymena thermophila. Elimination of H3K4 methylation (hht2-K4Q) and knockout of either of the ubiquitylation enzymes (delta-UBC2 and delta-BRE1) affects a broader spectrum of genes than elimination of H2B ubiquitylation (htb1-K115R).
Project description:Distinct classes of small RNAs are often selectively sorted to different Argonaute proteins. Various properties of small RNAs, such as length, terminal nucleotide, thermodynamic asymmetry and duplex mismatches, can impact sorting in different RNA silencing pathways in diverse eukaryotes. The developmentally regulated ~26-32 nt siRNAs, which are involved in programmed DNA elimination in Tetrahymena, show a strong bias for uracil at the 5' end. In this study, we analyzed loaded and unloaded populations of ~26-32 nt siRNAs by deep RNA sequencing. We show that the production process is the main determinant of size, whereas the 5' uracil bias is attributed not only to the process of loading siRNAs into the Argonaute protein Twi1p but also significantly to the initial processing of the siRNAs. We also show that both the loaded and the unloaded ~26-32 nt siRNAs have a strong bias for adenine as the 3rd base from the 3' terminus, suggesting that most of these siRNAs are direct Dicer products and little post-processing amplification of this class of siRNAs occurs. Further, we demonstrate that the siRNA-loading process in vivo can be deduced from the fraction of siRNAs with uracil as the first base. These findings provide biochemical bases for the attributes of ~26-32 nt siRNAs, which should help improve our understanding of their production and turnover in vivo. Examination of siRNA populations in wild-type and TWI1 KO Tetrahymena cells
