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MCB Accepts, published online ahead of print on 10 March 2008
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28/10/3313    most recent
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Mol. Cell. Biol. doi:10.1128/MCB.01900-07
Copyright (c) 2008, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

A Regulatory Role of the Rnq1 Non-Prion Domain for Prion Propagation and Polyglutamine Aggregates

Hiroshi Kurahashi, Masao Ishiwata, Shoichiro Shibata, and Yoshikazu Nakamura*

Department of Basic Medical Sciences, Institute of Medical Science, University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108-8639, Japan

* To whom correspondence should be addressed. Email: nak{at}ims.u-tokyo.ac.jp.


   Abstract

Prions are infectious, self-propagating protein conformations. Rnq1 is required for the yeast prion [PIN+], which is necessary for the de novo induction of a second prion, [PSI+]. Here we isolate a [PSI+]-eliminating mutant, Rnq1{Delta}100, that deletes the non-prion domain of Rnq1. Rnq1{Delta}100 inhibits not only [PSI+] prion propagation but also [URE3] prion and huntingtin's polyglutamine aggregate propagation in a [PIN+] background, but not in a [pin-] background. Rnq1{Delta}100, however, does not eliminate [PIN+]. These findings are interpreted as showing a possible involvement of Rnq1 prion in the maintenance of heterologous prions and polyQ aggregates. Rnq1 and Rnq1{Delta}100 form a SDS-stable and Sis1 (a Hsp40 chaperone protein)-containing co-aggregate in [PIN+] cells. Importantly, Rnq1{Delta}100 is highly QN-rich and prone to self-aggregate or co-aggregate with Rnq1 when co-expressed in [pin-] cells. However, the [pin-] Rnq1-Rnq1{Delta}100 co-aggregate does not represent a prion-like aggregate. These findings suggest that [PIN+] Rnq1-Rnq1{Delta}100 aggregates interact with other transmissible and non-transmissible amyloids to destabilize them, and that the non-prion domain of Rnq1 plays a crucial role to self-regulate the highly reactive QN-rich prion domain of Rnq1.







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