Enhancement of the seed-target recognition step in RNA silencing by a PIWI/MID domain protein.

ABSTRACT: Target recognition in RNA silencing is governed by the "seed sequence" of a guide RNA strand associated with the PIWI/MID domain of an Argonaute protein in RISC. Using a reconstituted in vitro target recognition system, we show that a model PIWI/MID domain protein confers position-dependent tightening and loosening of guide-strand-target interactions. Over the seed sequence, the interaction affinity is enhanced up to approximately 300-fold. Enhancement is achieved through a reduced entropy penalty for the interaction. In contrast, interactions 3' of the seed are inhibited. We quantified mismatched target recognition inside and outside the seed, revealing amplified discrimination at the third position in the seed mediated by the PIWI/MID domain. Thus, association of the guide strand with th

SUBMITTER: Parker JS 

PROVIDER: S-EPMC2642989 | biostudies-literature | 2009 Jan

REPOSITORIES: biostudies-literature