Cyclin A Is Redundant in Fibroblasts but Essential in Hematopoietic and Embryonic Stem Cells

摘要: Cyclins are regulatory subunits of cyclin-dependent kinases. Cyclin A, the first cyclin ever cloned, is thought to be an essential component cell-cycle engine. Mammalian cells encode two A-type cyclins, testis-specific A1 and ubiquitously expressed A2. Here, we tested requirement for A function using conditional knockout mice lacking both cyclins. We found that acute ablation in fibroblasts did not affect cell proliferation, but led prolonged expression another cyclin, E, across cycle. However, combined all A- E-type cyclins extinguished division. In contrast, was progression hematopoietic embryonic stem cells. Expression particularly high these compartments, which might render dependent on whereas E play redundant roles proliferation.