The exposure of cells, tissues and organs to "stress," such as elevated temperature, stimulates production of active heat stress transcription factors (HSF), which in turn, induce expression of genes regulated by stress promoters. Normally, the activity of stress promoters declines after cells, tissues and organs are returned to a normal condition. The present invention relates to molecular circuits that provide for sustained expression of a gene of interest subsequent to a single application of stress. Generally, the molecular circuits of the invention comprise (a) a first nucleic acid molecule that comprises a gene encoding a transcription factor and a first promoter or a combination promoter activatable by stress and by the transcription factor, wherein the first promoter or the combination promoter and the transcription factor gene are operably linked, and (b) a second nucleic acid molecule that comprises a gene of interest and a second promoter activatable by the transcription factor, wherein the second promoter and the gene of interest are operably linked.