Why molecular chaperones buffer mutational damage: a case study with a yeast Hsp40/70 system.

The malfunctioning of molecular chaperones may result in uncovering genetic variation. The molecular basis of this phenomenon remains largely unknown. Chaperones rescue proteins unfolded by environmental stresses and therefore they might also help to stabilize mutated proteins and thus mask damages.

Small fitness effects and weak genetic interactions between deleterious mutations in heterozygous loci of the yeast Saccharomyces cerevisiae.

Rare, random mutations were induced in budding yeast by ethyl methanesulfonate (EMS). Clones known to bear a single non-neutral mutation were used to obtain mutant heterozygotes and mutant homozygotes that were later compared with wild-type homozygotes. The average homozygous effect of mutation was an approximately 2% decrease in the growth rate.