Premature replication of late S period DNA regions in early S nuclei transferred to late S cytoplasm by fusion in Physarum polycephalum.
Fusion of a late S period plasmodium of Physarum polycephalum to an early S period plasmodium causes premature replication of late S replicating regions in the nuclei of the early S plasmodium. The extent of ahead-of-schedule replication of late S replicating regions in early S period nuclei increases to a plateau of 16-20% for fusions with 40-70 min of phase difference, then declines for larger phase differences. The stimulatory factors for late S replicative units are present only in late S plasmodia and appear to act only on late S regions. Once replicated, early S replicating regions are not stimulated to replicate again by fusion to a plasmodium entering the S period. Our data do not discriminate between anti-termination of replication by factors of stop sites on long replicons, and a sequential initiation of replication on new, possibly non-adjacent regions, but does provide evidence that the stimulatory factors are distinct from one another and specific for certain target replicative units.
D002455:Cell Division; D002459:Cell Fusion; D002467:Cell Nucleus / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism; D004261:DNA Replication; D009235:Myxomycetes / Q000378:metabolism*; D010804:Physarum / Q000254:growth & development / Q000378:metabolism*; D013997:Time Factors