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A yeast prion provides a mechanism for genetic variation and phenotypic diversity

Naturevolume 407pages477483 (2000) | Download Citation



A major enigma in evolutionary biology is that new forms or functions often require the concerted effects of several independent genetic changes. It is unclear how such changes might accumulate when they are likely to be deleterious individually and be lost by selective pressure. The Saccharomyces cerevisiae prion [PSI+] is an epigenetic modifier of the fidelity of translation termination, but its impact on yeast biology has been unclear. Here we show that [PSI+] provides the means to uncover hidden genetic variation and produce new heritable phenotypes. Moreover, in each of the seven genetic backgrounds tested, the constellation of phenotypes produced was unique. We propose that the epigenetic and metastable nature of [PSI+] inheritance allows yeast cells to exploit pre-existing genetic variation to thrive in fluctuating environments. Further, the capacity of [PSI+] to convert previously neutral genetic variation to a non-neutral state may facilitate the evolution of new traits.

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We thank members of the Lindquist lab and M. Jensen for discussion and comments on the manuscript, and V. Iyer, P.O. Brown, J. Henikoff and S. Henikoff for collaborative efforts and for allowing us to cite unpublished work. This research was supported by the Jane Coffin Childs Memorial Fund for Medical Research (H.L.T.), the National Institutes of Health and the Howard Hughes Medical Institute.

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  1. Department of Molecular Genetics and Cell Biology, Howard Hughes Medical Institute, The University of Chicago, Chicago, 60637, Illinois, USA

    • Heather L. True
    •  & Susan L. Lindquist


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