A Tetrahymena Piwi Bound to Mature tRNA 3 ' Fragments Activates the Exonuclease Xrn2 for RNA Processing in the Nucleus
Mary T Couvillion, Gergana Bounova, Elizabeth Purdom, Terence P Speed, Kathleen Collins
MOLECULAR CELL | CELL PRESS | Published : 2012
Emerging evidence suggests that Argonaute (Ago)/Piwi proteins have diverse functions in the nucleus and cytoplasm, but the molecular mechanisms employed in the nucleus remain poorly defined. The Tetrahymena thermophila Ago/Piwi protein Twi12 is essential for growth and functions in the nucleus. Twi12-bound small RNAs (sRNAs) are 3' tRNA fragments that contain modified bases and thus are attenuated for base pairing to targets. We show that Twi12 assembles an unexpected complex with the nuclear exonuclease Xrn2. Twi12 functions to stabilize and localize Xrn2, as well as to stimulate its exonuclease activity. Twi12 function depends on sRNA binding, which is required for its nuclear import. Depl..View full abstract
Awarded by NIH
Awarded by NATIONAL INSTITUTE OF GENERAL MEDICAL SCIENCES
This work was supported by NIH grant GM54198 (K.C.) and a predoctoral fellowship from the Genentech Foundation (M.T.C.). We thank members of the Collins lab for helpful discussion and Emily Egan for critical reading of the manuscript.