DNA synthesis by the isolated nuclear matrix from synchronized plasmodia of Physarum polycephalum.
Nuclear matrices were isolated from plasmodia of a true slime mold, Physarum polycephalum, and the DNA synthetic activity in vitro was examined. These matrices isolated in S-phase catalyzed DNA synthesis requiring Mg2+, deoxyribonucleoside 5'-triphosphates and ATP, without exogenous templates. The activity changed during S-phase with the rate of in vivo DNA replication. Product analysis by gel electrophoresis revealed that the matrices produced Okazaki fragments. These results suggest that DNA synthesis partially reflects in vivo DNA replication. DNA synthesis was sensitive to aphidicolin, heparin and N-ethylmaleimide, indicating involvement of the alpha-like DNA polymerase of Physarum. Exogenous addition of activated DNA stimulated DNA synthesis 4-10-fold and suggested that only some of the existing enzymes are involved in endogenous DNA synthesis. Matrices isolated in G2-phase were also associated with a similar DNA synthetic activity, but they did not produce Okazaki fragments in vitro. It is, therefore, concluded that nuclear matrices are associated with alpha-like DNA polymerase throughout the cell cycle, and that some of the enzymes participate in in vivo DNA replication in S-phase; thus, DNA replication is possibly controlled by this process. The relationship between DNA synthetic activities by the isolated nuclei and matrices was also discussed.
Shioda
M
M
Department of Physiological Chemistry and Nutrition, Faculty of Medicine, University of Tokyo, Japan.
Matsuzawa
Y
Y
Murakami-Murofushi
K
K
Ohta
J
J
D000255:Adenosine Triphosphate / Q000494:pharmacology; D002453:Cell Cycle; D002467:Cell Nucleus / Q000502:physiology* / Q000648:ultrastructure; D002474:Cell-Free System; D004247:DNA / Q000096:biosynthesis*; D004261:DNA Replication; D004259:DNA-Directed DNA Polymerase / Q000145:classification / Q000378:metabolism*; D004587:Electrophoresis, Agar Gel; D066298:In Vitro Techniques; D019384:Nucleic Acid Synthesis Inhibitors; D010804:Physarum / Q000502:physiology*; D013997:Time Factors
D019384:Nucleic Acid Synthesis Inhibitors; D000255:Adenosine Triphosphate; D004247:DNA; D004259:DNA-Directed DNA Polymerase