Tia1/Pub1 is a stress granule component carrying a Q/N-rich prion domain. We 
provide direct evidence that Tia1 forms a prion in yeast. Moreover, Tia1/Pub1 
acts cooperatively with release factor Sup35/eRF3 to establish a two-protein 
self-propagating state. This two-protein prion driven by the Q/N-rich prion 
domains of Sup35 and Tia1/Pub1 can be visualized as distinctive line structures 
along tubulin cytoskeleton. Furthermore, we find that tubulin-associated complex 
containing Pub1 and Sup35 oligomers normally exists in yeast, and its assembly 
depends on prion domains of Pub1 and Sup35. This Sup35/Pub1 complex, which also 
contains TUB1 mRNA and components of translation machinery, is important for the 
integrity of the tubulin cytoskeleton: PUB1 disruption and Sup35 depletion from 
the complex lead to cytoskeletal defects. We propose that the complex is 
implicated in protein synthesis at the site of microtubule assembly. Thus our 
study identifies the role for prion domains in the assembly of multiprotein 
complexes.