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EMBO reports 5, 2, 189–194 (2004)
doi:10.1038/sj.embor.7400070
AOP Published online: 16 January 2004
Characterization of the interactions between mammalian PAZ PIWI domain proteins and Dicer
Nasser Tahbaz1, 3, Fabrice A Kolb2, 4, Haidi Zhang2, 4, Katarzyna Jaronczyk1, 3, Witold Filipowicz2, 4 & Tom C Hobman1, 3
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1 Department of Cell Biology, University of Alberta, Edmonton, Alberta, Canada
2 Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland
3 Department of Cell Biology, University of Alberta, Edmonton, Alberta, Canada T6G 2H7
4 Friedrich Miescher Institute for Biomedical Research, POB 2542 4002 Basel, Switzerland
To whom correspondence should be addressed
Witold Filipowicz Tel: +41 61 6976993; Fax: +41 61 6973976; E-mail: filipowi@fmi.ch
Tom C Hobman Tel: 780 492 6485; Fax: 780 492 0450; E-mail: tom.hobman@ualberta.ca
Received 4 September 2003; Accepted 21 November 2003; Published online 16 January 2004.
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Abstract
PAZ PIWI domain (PPD) proteins, together with the RNA cleavage products of Dicer, form ribonucleoprotein complexes called RNA-induced silencing complexes (RISCs). RISCs mediate gene silencing through targeted messenger RNA cleavage and translational suppression. The PAZ domains of PPD and Dicer proteins were originally thought to mediate binding between PPD proteins and Dicer, although no evidence exists to support this theory. Here we show that PAZ domains are not required for PPD protein–Dicer interactions. Rather, a subregion of the PIWI domain in PPD proteins, the PIWI-box, binds directly to the Dicer RNase III domain. Stable binding between PPD proteins and Dicer was dependent on the activity of Hsp90. Unexpectedly, binding of PPD proteins to Dicer inhibits the RNase activity of this enzyme in vitro. Lastly, we show that PPD proteins and Dicer are present in soluble and membrane-associated fractions, indicating that interactions between these two types of proteins may occur in multiple compartments.
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