Msn2p/Msn4p-activation is essential for the recovery from freezing stress in yeast

Since it seems quite difficult for frozen cells to repair the damage caused by freezing, the adequate responses appear to be induced during and/or after the thawing process to recover from the damage due to freezing. In this study, the cellular events happening upon the return from freezing at −30 °C to a growth temperature (28 °C) were investigated. Yap1p, an oxidative stress-responsive transcription factor, was not activated in the thawed cells, indicating that no serious oxidative stress was generated in the frozen-thawed cells. On the other hand, Msn2p and Msn4p, general stress-responsive transcription factors, were activated in the thawed cells and caused the increased expression of a number of Msn2p/Msn4p-target genes including SOD1, SOD2, and several HSP genes. Since almost no expression of Msn2p/Msn4p-target genes was induced before thawing, these results indicate that Msn2p and Msn4p play a role during the recovery process from freezing.