RING1 and acute myeloid leukemia: However, Ash1l-deficient mice could survive even without quiescent HSCs, indicating that their function is most likely as a quality reservoir for stem cells that also can be used under extreme conditions such as cytotoxic stress or the stressful repopulation of an empty niche in another animal.130 Interestingly, the PRC1 component Ring1 mediates gene expression in quiescent B cells and prevents cell death of these resting cells.131 Also, in stem cells of acute myelogenous leukemia, Ring1 maintains the stemness of the cancer cells.132