In This Issue

摘要

A major hurdle in the therapeutic use of stem cells involves determining the internal and external factors that give them unique properties such as immortality and sustainability. One cluster of genes that might play an intrinsic role, called the Polycomb-group (PcG) genes, encodes a set of multiprotein complexes called PcG complex 1 and 2. Genetic studies suggest a role for PcG complex 1 in many types of stem cells, but the molecular functions of this complex remain unclear. To investigate the function of PcG complex 1, Motoaki Ohtsubo el al. focused on Geminin-a protein recruited to PcG complex 1 and known to suppress DNA replication licensing-in mouse hematopoietic stem cells (HSCs). They found that PcG complex 1 acts as an E3 ubiquitin ligase for Geminin, tagging Geminin to induce its degradation and facilitating turnover of the protein. Because Geminin expression is higher in HSCs, Ohtsubo et al. say that it may be a key support molecule for HSCs, regulating their proliferation, differentiation, and genomic stability. The authors also suggest that regulation of Geminin by PcG complex 1 could provide a potential target for altering stem cell properties for therapeutic use. - M.M.