Physical relationship between a gene and its origin of replication in Physarum polycephalum.
Taking advantage of the natural synchrony of the S-phase within the plasmodium of Physarum polycephalum, we extracted highly synchronous DNA samples at precise time points in early S-phase. We then separated, by electrophoresis under denaturating conditions, the newly synthesized DNA strands of the nascent chromosomal replicons from the parental DNA template. Using the cDNA clone of the early-replicating LAV1-2 gene as a probe, we could establish by filter hybridization that the elongation rate of the replicon which encompasses this gene is constant, at a rate of 1 kb/min during the first 30 min of S-phase. The smallest replication intermediate (RI) that we have detected by probing with the LAV1-2 cDNA was 5 kb long, suggesting that the LAV1-2 gene and its origin of replication are closely associated within the chromosome. This procedure should facilitate the mapping of replication origins within the genome of Physarum.
Benard
M
M
Laboratoire de Biologie et Ultrastructure du Noyau, Institut de Recherches Scientifiques sur le Cancer, Villejuif, France.
Pierron
G
G
D015342:DNA Probes; D004261:DNA Replication; D004262:DNA Restriction Enzymes; D004271:DNA, Fungal / Q000235:genetics* / Q000302:isolation & purification; D015246:Deoxyribonuclease EcoRI; D015870:Gene Expression; D005800:Genes, Fungal; D007399:Interphase; D007700:Kinetics; D009693:Nucleic Acid Hybridization; D010804:Physarum / Q000235:genetics*; D012150:Polymorphism, Restriction Fragment Length
D015342:DNA Probes; D004271:DNA, Fungal; D004262:DNA Restriction Enzymes; D015246:Deoxyribonuclease EcoRI