A new colour assay for [URE3] prion in a genetic background used to score for the [PSI⁺] prion.

Most scoring assays for yeast prions are dependent on specific genetic markers and constructs that differ for each prion. Here we describe a simple colour assay for the [URE3] prion that works in the 74D-964 strain frequently used to score the [PSI(+)] prion. Although this assay can only be used to score for [URE3] in the [psi(-)] version of the strain, it makes it easier to examine the effects of host mutations or environmental changes on [URE3] or [PSI(+)] using a colour assay in the identical genetic background.