SUMMARY PARAGRAPH for HSP42 HSP26 and HSP42 encode the cytosolic
members of the small heat shock protein (sHSP) family of
molecular chaperones (6, 2). sHSPs bind and prevent unfolded
substrate proteins from irreversibly forming large protein
aggregates. Bound substrate proteins can eventually be released
and refolded in either a spontaneous or chaperone-assisted
manner (reviewed in 7). Hsp42p functions in both unstressed and
stressed cells, while Hsp26p activity is found only under stress
conditions; the target substrate profiles of the two chaperones
overlap by approximately 90% (4). Null mutations in hsp26 or
hsp42 cause abnormal cell morphology that resembles the effects
of dehydration, aging, cytoskeleton damage, or cell wall damage
(4). A basal level of the HSP42 transcript is found under all
conditions but expression is induced by stresses such as heat
shock, salt shock, and starvation (2). This upregulation of
transcription is mediated by the transcription factors Hsf1p and
Msn2p/Msn4p which respective