Prions beget prions:: the [PIN+] mystery!

Prions are infectious proteins. [PIN+] is a non-chromosomal genetic element of Saccharomyces cerevisiae that is necessary for the de novo induction of the [PSI+] prion. Recently, [PIN+] has been found to be itself a prion of the Rnq1 protein. [URE3], another yeast prion, can also promote [PSI+] generation. Thus, one prion can promote the generation of another.