Transcriptional memory is a biological phenomenon, initially discovered in yeast, [1] during which cells primed with a particular cue show increased rates of gene expression after re-stimulation at a later time. This event was shown to take place: in yeast during growth in galactose [1] [2] and inositol starvation; [3] plants during environmental stress; [4] [5] [6] in mammalian cells during LPS [7] and interferon [8] [9] [10] induction. Prior work has shown that certain characteristics of chromatin may contribute to the poised transcriptional state allowing faster re-induction. These include: activity of specific transcription factors, [11] [12] [13] retention of RNA polymerase II at the promoters of poised genes, [9] activity of chromatin remodeling complexes, [2] propagation of H3K4me2 [8] [13] and H3K36me3 [10] histone modifications, occupancy of the H3.3 histone variant, [10] as well as binding of nuclear pore components. [9] [14] Moreover, locally bound cohesin was shown to inhibit establishment of transcriptional memory in human cells during interferon gamma stimulation. [15]
