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A Tetrahymena Hsp90 co‐chaperone promotes si RNA loading by ATP ‐dependent and ATP ‐independent mechanisms
Author(s) -
Woehrer Sophie L,
Aronica Lucia,
Suhren Jan H,
Busch Clara JanaLui,
Noto Tomoko,
Mochizuki Kazufumi
Publication year - 2015
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.15252/embj.201490062
Subject(s) - biology , tetrahymena , microbiology and biotechnology , chaperone (clinical) , hsp90 , biochemistry , biophysics , heat shock protein , gene , medicine , pathology
The loading of small interfering RNA s (si RNA s) and micro RNA s into Argonaute proteins is enhanced by Hsp90 and ATP in diverse eukaryotes. However, whether this loading also occurs independently of Hsp90 and ATP remains unclear. We show that the Tetrahymena Hsp90 co‐chaperone Coi12p promotes si RNA loading into the Argonaute protein Twi1p in both ATP ‐dependent and ATP ‐independent manners in vitro . The ATP ‐dependent activity requires Hsp90 and the tetratricopeptide repeat ( TPR ) domain of Coi12p, whereas these factors are dispensable for the ATP ‐independent activity. Both activities facilitate si RNA loading by counteracting the Twi1p‐binding protein Giw1p, which is important to specifically sort the 26‐ to 32‐nt si RNA s to Twi1p. Although Coi12p lacking its TPR domain does not bind to Hsp90, it can partially restore the si RNA loading and DNA elimination defects of COI 12 knockout cells, suggesting that Hsp90‐ and ATP ‐independent loading of si RNA occurs in vivo and plays a physiological role in Tetrahymena .