Replication timing of 10 developmentally regulated genes in Physarum polycephalum.
We have tested the hypothesis which stipulates that only early-replicating genes are capable of expression. Within one cell type of Physarum - the plasmodium - we defined the temporal order of replication of 10 genes which were known to be variably expressed in 4 different developmental stages of the Physarum life cycle. Southern analysis of density-labeled, bromodesoxyuridine-substituted DNA reveals that 4 genes presumably inactive within the plasmodium, were not restricted to any temporal compartment of S-phase: 1 is replicated in early S-phase, 2 in mid S-phase and 1 in late S-phase. On the other hand, 4 out of 6 active genes analysed are duplicated early, with the first 30% of the genome. Surprisingly, the two others active genes are replicated late in S-phase. By gene-dosage analysis, based on quantitation of hybridization signals from early and late replicating genes throughout S-phase, we could pinpoint the replication of one of these two genes at a stage where 80-85% of the genome has duplicated. Our results demonstrate that late replication during S-phase does not preclude gene activity.
Pierron
G
G
Institut de Recherches Scientifiques sur le Cancer, Villejuif, France.
Benard
M
M
Puvion
E
E
Flanagan
R
R
Sauer
H W
HW
Pallotta
D
D
D015139:Blotting, Southern; D004261:DNA Replication; D004271:DNA, Fungal / Q000096:biosynthesis / Q000502:physiology*; D004303:Dosage Compensation, Genetic; D005796:Genes; D005800:Genes, Fungal; D007399:Interphase; D009693:Nucleic Acid Hybridization; D010804:Physarum / Q000235:genetics / Q000254:growth & development*
D004271:DNA, Fungal