The heat shock response (HSR) is a highly conserved cellular process that promotes survival during stress. A hallmark of the HSR is the rapid induction of heat shock proteins (HSPs), such as HSP-70, by transcriptional activation. Once the stress is alleviated, HSPs return to near basal levels through incompletely understood mechanisms. Here, we show that the microRNA pathway acts during heat shock recovery in Caenorhabditis elegans. We present evidence that
hsp-70 is repressed by miR-85 and sequences in the
hsp-70 3'UTR that include target sites for this miRNA. Regulation of
hsp-70 by miR-85 was found to be particularly important during recovery from HS, as animals that lacked miR-85 or its target sites in the
hsp-70 3'UTR overexpressed HSP-70 and exhibited reduced viability. In summary, our findings show that down-regulation of
hsp-70 by miR-85 after HS promotes survival, highlighting a previously unappreciated role for the miRNA pathway during recovery from an episode of stress.