Most, but not all, yeast strains in the deletion library contain the [PIN(+)] prion

The yeast deletion library is a collection of over 5100 single gene deletions that has been widely used by the yeast community. The presence of a non-Mendelian element, such as a prion, within this library could affect the outcome of many large-scale genomic studies. We previously showed that the deletion library parent strain contained the [PIN(+)] prion. [PIN(+)] is the misfolded infectious prion form of the Rnq1 protein that displays distinct fluorescent foci in the presence of RNQ1-GFP and exists in different physical conformations, called variants. Here, we show that over 97% of the library deletion strains are [PIN(+)]. Of the 141 remaining strains that have completely (58) or partially (83) lost [PIN(+)], 139 deletions were able to efficiently maintain three different [PIN(+)] variants despite extensive growth and storage at 4 degrees C. One strain, cue2Delta, displayed an alteration in the RNQ1-GFP fluorescent shape, but the Rnq1p prion aggregate shows no biochemical differences from the wild-type. Only strains containing a deletion of either HSP104 or RNQ1 are unable to maintain [PIN(+)], indicating that 5153 non-essential genes are not required for [PIN(+)] propagation.