Gtsf1 and Gtsf1L bind Siwi and BmAgo3, respectively, and activate each PIWI protein. (A) Western blot analysis of immunoprecipitated tagged-Gtsf1 and -Gtsf1L from BmN4 cells. After immunoprecipitation, the sample was divided into two and one half was treated with RNase A. (B,C) In vitro target cleavage assay of immunoprecipitated Siwi (B) or BmAgo3 (C) from BmN4 cells. Target RNA against an abundant endogenous Siwi- (B) or BmAgo3-bound (C) piRNA was used. The graphs show the fraction cleaved normalized to that of the buffer-only sample. The values are means of three independent experiments. Dots, individual values. Paired t-test with Bonferroni adjusted P-values are 0.0046 (Buffer vs. Gtsf1 in B), 0.0049 (Gtsf1 vs. Gtsf1L in B), 0.04 (Buffer vs. Gtsf1L in C), and 0.039 (Gtsf1 vs. Gtsf1L in C). N.S., not significant.
