Figure 2.

p53 prion-like aggregates can be transferred by cytoduction, from prion donor cells, to non-prion recipient cells expressing either wild-type p53 or mutant p53-R175H

(A) Cartoon illustrating cytoduction. Donor with green nucleus and pink dotted cytoplasm is mated with recipient with black nucleus and blue diagonals cytoplasm. Upon cell fusion the cytoplasms mix, but often nuclei fail to fuse because of the presence of the kar1 mutation that inhibits karyogamy. Selection is for cytoductants that bud off of the fused heterokaryon, which contain just the recipient's nucleus but a fusion of the donor and recipient cytoplasms.

(B) Data showing transmission of p53 prion via cytoduction. Subclones of L3672 containing p53 prions as well as isogenic control L3671 lacking prions were used as cytoplasmic donors by crossing them to a recipient non-prion kar1 strain, L3663, transformed with pGPD-p53-EYFP or pGPD-p53-R175H-EYFP. Cytoductants, with mixed cytoplasm but recipient nuclei, were assayed for cytoplasmic fluorescent foci. All those obtained from the non-prion donor showed >95% cells with only nuclear fluorescence, whereas 38/44 and 23/28 of the cytoductants obtained from the prion donor, respectively, into wild-type or R175H p53 recipients showed ~30%–40% cells with cytoplasmic fluorescent foci. The dramatic difference in the fraction of cells with foci (~30%–40% versus approximately <5%) seen in the cytoductants made it easy to score them as containing or lacking the prion, as there were no cytoductants with an intermediate level of foci. Scale bar, 5 μM.

See also Tables S1 and S2 for a description of strains and plasmids.