Intracytoplasmic signals for DNA replication in lymphocyte proliferation.
Cytoplasmic extracts prepared from continuously proliferating lymphoblastoid cells, as well as mitogen-activated normal lymphocytes, contain a protein or proteins (ADR) capable of inducing DNA synthesis in isolated quiescent nuclei. Lymphocytes obtained from aged donors with depressed proliferative responses have normal levels of ADR, but depressed nuclear responses to exogenous ADR, suggesting a nuclear defect in these cells. In no instance could an effect of ADR on intact cells be demonstrated. Moreover, it is not released into the extracellular milieu by cells that contain it. These observations suggest that it serves as an intracellular mitogenic signal in replicating cells. Thus, it may be an important intermediate in the pathway leading from cell membrane activation to nuclear activation.
D000818:Animals; D002453:Cell Cycle; D002455:Cell Division; D002467:Cell Nucleus / Q000502:physiology; D003593:Cytoplasm / Q000502:physiology; D004261:DNA Replication; D006801:Humans; D008213:Lymphocyte Activation; D008934:Mitogens; D011898:Ranidae
D008934:Mitogens