Analysis of Piwi-Loaded Small RNAs in Terahymena

: Scan RNAs (scnRNAs) are developmentally regulated siRNAs of ~26-32 nucleotides in length that are involved in programmed DNA elimination in Tetrahymena. scnRNAs are loaded onto the Piwi-related protein Twi1p and 2'-O-methylated at their 3' termini. We describe two alternative strategies for analyzing the Twi1p-loaded scnRNAs: preparation of loaded scnRNAs by immuno-purification of the Twi1p-scnRNA complex and exclusion of non-methylated scnRNAs during cDNA library construction using periodate oxidation.