An important finding by Chernoff, in a collaboration between the Liebman and Lindquist laboratories, was that a protein chaperone was required for to be maintained. Because the only function of chaperones is to help proteins fold properly, this finding strongly supported Wickner's hypothesis that [PSI+ was a heritable protein state (i.e. a prion). Likewise, this finding also provided evidence for the general hypothesis that prions, including the originally proposed mammalian PrP prion, are heritable forms of protein. Because of the action of chaperones, especially Hsp104, proteins that code for and [URE3 can convert from non-prion to prion forms. For this reason, yeast prions are good models for studying factors like chaperones that affect protein aggregation. Also, the IPOD is the sub-cellular site to which amyloidogenic proteins are sequestered in yeast, and where prions like [PSI+] may undergo maturation. Thus, prions also serve as substrates to understand the intracellular processing of protein aggregates such as amyloid.