In the yeast Saccharomyces cerevisiae, the non-Mendelian inherited genetic
element [URE3] behaves as a prion. A hypothesis has been put forward which
states that [URE3] arises spontaneously from its cellular isoform Ure2p (th
e product of the URE2 gene), and propagates through interactions of the N-t
erminal domain of the protein, thus leading to its aggregation and loss of
function. In the present study, various N- and C-terminal deletion mutants
of Ure2p were constructed and their cross-interactions were tested in vitro
and in vivo using affinity binding and a two-hybrid analysis. We show that
the self-interaction of the protein is mediated by at least two domains, c
orresponding to the first third of the protein (the so-called prion-forming
domain) and the C-terminal catalytic domain.