By. Chu et al., HEAT-SHOCK INHIBITS RELEASE OF THE SIGNAL RECOGNITION PARTICLE FROM THE ENDOPLASMIC-RETICULUM IN BARLEY ALEURONE LAYERS, The Journal of biological chemistry, 272(11), 1997, pp. 7306-7313
When barley (Hordeum vulgare) aleurone layers are subjected to heat sh
ock there is a selective degradation of the normally stable mRNAs enco
ding secreted proteins, Messages for nonsecreted proteins are not degr
aded. The synthesis of heat shock proteins is not required for this se
lective message degradation. Our hypothesis explaining this phenomenon
is that a component of the early steps in the synthesis of secreted p
roteins is damaged by heat shock, resulting in a selective halt in tra
nslation on secretory mRNAs, which may in turn lead to degradation of
those messages, The first committed step in the synthesis of secreted
proteins is the binding of the nascent signal sequence to the signal r
ecognition particle. We have obtained cDNA clones and antibodies for t
he barley 54-kDa subunit of the signal recognition particle. In cell f
ractionation experiments, more signal recognition particle was bound t
o the endoplasmic reticulum membranes and less was in the free particl
e fraction following a heat shock. The results suggest that heat shock
inhibits the release of the signal recognition particle from the endo
plasmic reticulum. This would, in turn, inhibit the resumption of tran
slation and may be the underlying cause of the secretory message degra
dation.