In Vitro Propagation of the Prion-Like State of Yeast Sup35 Protein

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Science  18 Jul 1997:
Vol. 277, Issue 5324, pp. 381-383
DOI: 10.1126/science.277.5324.381

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The yeast cytoplasmically inherited genetic determinant [PSI +] is presumed to be a manifestation of the prion-like properties of the Sup35 protein (Sup35p). Here, cell-free conversion of Sup35p from [psi ] cells (Sup35ppsi ) to the prion-like [PSI +]-specific form (Sup35pPSI +) was observed. The conversion reaction could be repeated for several consecutive cycles, thus modeling in vitro continuous [PSI +] propagation. Size fractionation of lysates of [PSI +] cells demonstrated that the converting activity was associated solely with Sup35pPSI + aggregates, which agrees with the nucleation model for [PSI +] propagation. Sup35pPSI + was purified and showed high conversion activity, thus confirming the prion hypothesis for Sup35p.

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