Fig. 1.

Basic steps in prion formation and propagation. Soluble proteins interact to form non-amyloid oligomers (step 1). These aggregates undergo a structural conversion to form amyloidogenic oligomers (step 2). The amyloidogenic aggregates recruit additional soluble proteins to form amyloid fibrils and to grow these fibrils (step 3). Fragmentation of these fibrils (step 4) creates new fiber ends for growth, while also creating new independently segregating aggregates to offset dilution by cell division