K562 cells implicate increased chromatin accessibility in Alu transcriptional activation

Alu repeats in K562 cells are unusually hypomethylated and far more activel y transcribed than those in other human cell lines and somatic tissues. Als o, the level of Alu RNA in K562 cells is relatively insensitive to cell str esses, namely heat shock, adenovirus infection and treatment with cyclohexi mide, which increase the abundance of Alu RNA in HeLa and 293 cells. Recent advances in understanding the interactions between DNA methylation, transc riptional activation and chromatin conformation reveal reasons for the cons titutively high level of Alu expression in K562 cells, Methylation represse s transcription of transiently transfected Alu templates in all cell lines tested but cell stresses do not relieve this repression suggesting that the y activate Alu transcription through another pathway, A relatively large fr action of the Alus within K562 chromatin is accessible to restriction enzym e cleavage and cell stresses increase the chromatin accessibility of Alus i n HeLa and 293 cells, Cell stress evidently activates Alu transcription by rapidly remodeling chromatin to recruit additional templates.