title: Multiple forms of nuclear deoxyribonucleic acid polymerases and their relationship with the soluble enzyme.
abstract: 1. DNA polymerase from nuclear and supernatant fractions of cultured mouse L929 cells was fractionated on columns of Sephadex G-200, Sepharose 4B and of DEAE-cellulose. Several peaks of activity are found on Sephadex chromatography and the distribution of activity between these depends on: (a) the source of the enzyme, i.e. nuclear or supernatant fraction; (b) the mode of extraction of the enzyme from the nucleus; (c) the amount of enzyme applied to the column. 2. The DNA polymerase activity in the lower-molecular-weight peaks (approximate molecular weights are 35000, 70000 and 140000) is firmly bound within the cell nucleus and shows a preference for native DNA as template, whereas the high-molecular-weight peak (peak I, molecular weight 250000 or greater) is found in supernatant fractions and shows greater activity with a denatured DNA template. 3. During periods of DNA synthesis the high-molecular-weight enzyme becomes more firmly bound within the nucleus. 4. Peak I enzymic activity is relatively unstable and is inhibited by thiol-blocking reagents and deoxycholate, but it is stimulated by univalent cations. 5. Very little endonuclease is present in the polymerase preparations, but a very active exonuclease and nucleoside diphosphokinase are present. On Sephadex chromatography, however, it was shown that the immediate precursors for DNA synthesis, at least by peak I enzyme, are the deoxyribonucleoside triphosphates. 6. Attempts to decrease the molecular weight of the peak I enzyme while still retaining activity failed.
mesh_terms: D000818:Animals; D002247:Carbon Isotopes; D002455:Cell Division; D002460:Cell Line; D002467:Cell Nucleus / Q000201:enzymology*; D002848:Chromatography, DEAE-Cellulose; D002850:Chromatography, Gel; D004247:DNA; D004254:DNA Nucleotidyltransferases / Q000037:antagonists & inhibitors / Q000302:isolation & purification / Q000378:metabolism*; D003840:Deoxycholic Acid; D004720:Endonucleases / Q000378:metabolism; D005092:Exonucleases / Q000378:metabolism; D005347:Fibroblasts / Q000166:cytology / Q000201:enzymology; D008566:Membranes / Q000201:enzymology; D051379:Mice; D009691:Nucleic Acid Denaturation; D009711:Nucleotides; D010770:Phosphotransferases / Q000378:metabolism; D011485:Protein Binding; D012995:Solubility; D013439:Sulfhydryl Reagents; D013698:Templates, Genetic; D014316:Tritium
chemical_list: D002247:Carbon Isotopes; D009711:Nucleotides; D013439:Sulfhydryl Reagents; D003840:Deoxycholic Acid; D014316:Tritium; D004247:DNA; D010770:Phosphotransferases; D004254:DNA Nucleotidyltransferases; D004720:Endonucleases; D005092:Exonucleases