Effect of over-expressed hsp26 on cell growth of yeast.

Mammalian small heat shock protein (s-hsp) has been suggested to participate not only in stress tolerance but also in the growth regulation and differentiation of cells. To confirm the role of s-hsp in cell growth, we investigated the relationship between the expression of hsp26 and yeast cell growth. Cells lacking constitutive hsp70, ssa1ssa2, have been known to have a poor growth rate and to over-express hsp26 and some other hsps. We obtained several cell clones of ssa1ssa2 whose doubling times were different from one another. The amount of hsp26 was closely linked to the doubling time of ssa1ssa2 cells. This result suggests that the expression of hsp26 modulates the growth rate of yeast cells lacking constitutive hsp70, similarly to mammalian cells.