title: Is the initiation of macronuclear DNA synthesis in Euplotes dependent on micronuclear functions?
abstract: To determine whether the micronucleus makes essential contributions during asexual reproduction, observations were made on cells of Euplotes octocarinatus from which the micronucleus had been removed with a micropipette. Most cells underwent one postenucleation division, then became arrested in macronuclear G1, slowed down in food uptake, developed macronuclear deformations, and finally died. Such cells could be rescued if a micronucleus was reimplanted before macronuclear deformations had developed. When provided with a new micronucleus, cells initiated macronuclear DNA synthesis about 12-16 h later. The data suggest that the micronucleus is involved in the control of the cell's transition from macronuclear G1 to S, and a model is proposed which postulates that in Euplotes macronuclear DNA synthesis is initiated when a micronucleus-encoded "initiator protein" has accumulated to a critical amount.
mesh_terms: D000818:Animals; D002453:Cell Cycle; D002467:Cell Nucleus / Q000502:physiology*; D002470:Cell Survival; D016798:Ciliophora / Q000378:metabolism / Q000502:physiology*; D004261:DNA Replication; D005247:Feeding Behavior; D012098:Reproduction