Figure 2. Transcriptional memory takes several forms.
Inducible genes that are activated (or repressed) by a stressor respond rapidly but transiently to stressor. However, in some cases transcriptional memory of stress exposure forms at stress-responsive genes. Transcriptional memory can take one of four forms. In sustained activation, genes that are induced by a stressor can remain at high levels of transcription instead of returning to a baseline state. In sustained repression, genes repressed by a stressor remain repressed, instead of returning to a baseline state. In positive priming, genes induced by a stressor return to baseline after stress ceases, but induction is faster or stronger on re-stimulation. In negative priming, genes induced by a stressor return to baseline after stress ceases, but induction is decreased or absent on re-stimulation.