文摘
RNAi is a highly conserved mechanism in almost every eukaryote with a few exceptions including the model organism Saccharomyces cerevisiae. A recent study showed that the introduction of the two core components of canonical RNAi systems, Argonaute and Dicer, from another budding yeast, Saccharomyces castellii, restores RNAi in S. cerevisiae. We report here that a functional RNAi system can be reconstituted in yeast with the introduction of only S. castellii Dicer and human Argonaute2. Interestingly, whether or not TRBP2 was present, human Dicer was unable to restore RNAi with either S. castellii or human Argonaute. Contrary to previous reports, we find that human Dicer, TRBP2 and Argonaute2 are not sufficient to reconstitute RNAi in yeast when bona fide RNAi precursors are co-expressed. We and others have previously reported that Hsp90 regulates conformational changes in human and Drosophila Argonautes required to accommodate the loading of dsRNA duplexes. Here we show that the activities of both human and S. castellii Argonaute are subject to Hsp90 regulation in S. cerevisiae. In summary, our results suggest that regulation of the RNAi machinery by Hsp90 may have evolved at the same time as ancestral RNAi.
