Hairy And Enhancer Of Split 1 (HES1)

HES1 belongs to a family of basic helix-loop-helix (bHLH) proteins that are essential for neurogenesis, myogenesis, hematopoiesis, and sex determination. HES1 is a transcriptional repressor for a number of genes, but it can also function as a transcriptional activator. Increased expression of the gene encoding HES1 was required for quiescence to be reversible, because HES1 prevented both premature senescence and inappropriate differentiation in quiescent fibroblasts. In some human tumors, the HES1 pathway was activated, which allowed these cells to evade differentiation and irreversible cell cycle arrest. HES1 safeguards against irreversible cell cycle exit both during normal cellular quiescence and pathologically in the setting of tumorigenesis.