title: Conversion of partially single-stranded replicating DNA to double-stranded DNA is delayed in megaloblastic anaemia.
abstract: DNA from phytohaemagglutinin-stimulated lymphocytes which had been pulse-labelled for 1 min with [3H]deoxycytidine eluted as partially single-stranded DNA from columns of benzoylated napthoylated DEAE-cellulose. The label was transferred progressively into the double-stranded DNA fraction upon incubation in the presence of unlabelled deoxycytidine. The rate of transfer was slower in untreated lymphocytes from patients with megaloblastic anaemia than in corresponding control cells. A similar delay was also observed in normal lymphocytes treated with methotrexate or hydroxyurea. A close temporal correlation between the joining of Okazaki pieces (measured by alkaline sucrose gradients) and the transfer of the pulse label to double-stranded DNA suggested that the latter process represented the filling of gaps between Okazaki pieces. We suggest that this gap-filling step is retarded in megaloblastic anaemia and in cells treated with methotrexate or hydroxyurea.
mesh_terms: D000748:Anemia, Macrocytic / Q000097:blood*; D000749:Anemia, Megaloblastic / Q000097:blood*; D002846:Chromatography, Affinity; D004261:DNA Replication; D004277:DNA, Single-Stranded / Q000097:blood*; D006801:Humans; D006918:Hydroxyurea / Q000494:pharmacology; D007700:Kinetics; D008214:Lymphocytes / Q000187:drug effects / Q000378:metabolism*; D008727:Methotrexate / Q000494:pharmacology
chemical_list: D004277:DNA, Single-Stranded; D006918:Hydroxyurea; D008727:Methotrexate