Mapping of a Physarum chromosomal origin of replication tightly linked to a developmentally-regulated profilin gene.
We compared the pattern of replication of two cell-type specific profilin genes in one developmental stage of the slime mold Physarum polycephalum. Taking advantage of the natural synchrony of S-phase within the plasmodium, we established that the actively transcribed profilin P gene is tightly linked to a chromosomal replication origin and is replicated at the onset of S-phase. In contrast, the inactive profilin A gene is not associated with a replication origin and it is duplicated in mid S-phase. Mapping by two-dimensional gel electrophoresis defines a short DNA fragment in the proximal upstream region of the profilin P gene from which bidirectional replication is initiated. We further provide an estimate of the kinetics of elongation of the replicon and demonstrate that the 2 alleles of the profilin P gene are coordinately replicated. All these results were obtained on total DNA preparations extracted from untreated cells. They provide a strong evidence for site specific initiation of DNA replication in Physarum.
Bénard
M
M
Laboratoire de Biologie et Ultrastructure du Noyau, UPR 272, CNRS, Villejuif, France.
Pierron
G
G
D000818:Animals; D015139:Blotting, Southern; D015825:Chromosomes, Fungal / Q000378:metabolism; D003285:Contractile Proteins / Q000235:genetics; D004261:DNA Replication / Q000235:genetics*; D004271:DNA, Fungal / Q000235:genetics; D015180:Electrophoresis, Gel, Two-Dimensional; D005656:Fungal Proteins / Q000235:genetics*; D015966:Gene Expression Regulation, Fungal / Q000502:physiology; D008840:Microfilament Proteins / Q000235:genetics*; D016839:Physarum polycephalum / Q000235:genetics*; D051304:Profilins; D015800:Protozoan Proteins / Q000235:genetics*
D003285:Contractile Proteins; D004271:DNA, Fungal; D005656:Fungal Proteins; D008840:Microfilament Proteins; D051304:Profilins; D015800:Protozoan Proteins