Determining the effect of SSB on [LSB+] prion-based stress memory
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Prions are self-perpetuating protein isoforms, that are usually based on ordered fibrous protein aggregates (amyloids), cause disease in humans and control non-Mendelian heritable traits in yeast. Formation and loss of yeast prions are modulated by environmental and physiological conditions, including heat stress. [LSB+], a metastable prion generated by the cytoskeleton-associated protein Lsb2 and influencing aggregation of other proteins, is induced by heat stress and persists in a fraction of yeast cells for a number of cell generations after stress, thus generating a cellular memory of stress. Chaperone proteins control protein folding, play an important role in adaptation during stress conditions, and are involved in prion formation and propagation. Ssb is member of the Hsp70 chaperone family and is normally associated with translating ribosomes. Previous studies in our lab indicated that Hsp70-Ssb has an anti-prion effect. We show that the formation and mitotic stability of the [LSB+] prion are greatly increased in the absence of Ssb. This links the ribosome-associated chaperone machinery to the cellular memory of stress.