formation of [PSI+] through a templating mechanism. Two modified versions of Sup35 have been created that can induce PSI+ in the absence of [PIN+] when overexpressed. One version was created by digestion of the gene with the restriction enzyme Bal2, which results in a protein consisting of only the M and N portions of Sup35. The other is a fusion of Sup35NM with HPR, a human membrane receptor protein. Epigenetics Prions act as an alternative form of non-Mendelian, phenotypic inheritance due to their self-templating ability. This makes prions a metastable, dominant mechanism for inheritance that relies solely on the conformation of the protein. Many proteins containing prion domains play a role in gene expression or RNA binding, which is how an alternative conformation can give rise to phenotypic variation. For example, the [psi-] state of Sup35 in yeast is a translation termination factor. When Sup35 undergoes a conformational change to the [PSI+] prion state, it forms amyloid fibrils and is sequestered, leading to more frequent stop codon read-through and the development of novel phenotypes. With over 20 prion-like domains identified in yeast, this gives rise to the opportunity for a significant amount of variation from a single proteome. It has been posited that this increased variation gives a selectable advantage to a population of genetically homogeneous yeast. List of characterized prions [*The original paper that proposed Mca1 is a prion was retracted ] See also Prion Sup35p Epigenetics Amyloid Proteopathy JUNQ and IPOD References Prions Fungal proteins