title: Rapid incorporation of label from ribonucleoside disphosphates into DNA by a cell-free high molecular weight fraction from animal cell nuclei.
abstract: A readily sedimentable nuclear fraction from Chinese hamster embryo fibroblast (CHEF/18) cells catalyzes incorporation of 14C-rCDP into DNA. Data indicated that this incorporation is made possible by the conversion of rCDP into a small and functionally compartmentalized, rather than a large and freely diffusible, pool of dCTP. This catalytically active sedimentable fraction from S phase CHEF/18 cells or actively replicating calf thymus cells contains nascent and template DNA, and numerous enzymes required for DNA biosynthesis including ribonucleoside diphosphate reductase, thymidylate synthetase, dihydrofolate reductase, DNA methylase, topoisomerase and DNA polymerase. We have named this catalytically active macromolecule the replitase. The replitase fraction contained spherical particles with a diameter of approximately 24 to 30 nm and had an estimated molecular weight on the order of 5 X 10(6).
mesh_terms: D000818:Animals; D002460:Cell Line; D002467:Cell Nucleus / Q000201:enzymology*; D006224:Cricetinae; D003565:Cytidine Diphosphate / Q000378:metabolism*; D003597:Cytosine Nucleotides / Q000378:metabolism*; D004247:DNA / Q000096:biosynthesis*; D004261:DNA Replication; D004259:DNA-Directed DNA Polymerase / Q000378:metabolism; D003845:Deoxycytosine Nucleotides / Q000378:metabolism; D005347:Fibroblasts; D007399:Interphase; D008970:Molecular Weight; D009097:Multienzyme Complexes / Q000378:metabolism*; D009701:Nucleoside-Diphosphate Kinase / Q000378:metabolism; D012262:Ribonucleoside Diphosphate Reductase / Q000378:metabolism; D013347:Subcellular Fractions; D013762:Tetrahydrofolate Dehydrogenase / Q000378:metabolism; D013940:Thymidylate Synthase / Q000378:metabolism
chemical_list: D003597:Cytosine Nucleotides; D003845:Deoxycytosine Nucleotides; D009097:Multienzyme Complexes; C037117:replitase; C024107:2'-deoxycytidine 5'-triphosphate; D003565:Cytidine Diphosphate; D004247:DNA; D012262:Ribonucleoside Diphosphate Reductase; D013762:Tetrahydrofolate Dehydrogenase; D013940:Thymidylate Synthase; D009701:Nucleoside-Diphosphate Kinase; D004259:DNA-Directed DNA Polymerase