title: Misincorporation of deoxyuridine in human cells: consequences of antifolate exposure.
abstract: Treatment of B and T lymphoblastoid cell lines (SB and MOLT-4, respectively) and a promyelocytic leukemia cell line (HL-60) with the lipid soluble antifolate, 2,4-diamino-5-methyl-6-(2',5'-dimeth-oxybenzyl) -pyrido (2,4-d) pyrimidine (BW301U), led to drug dose-dependent inhibition of [3H]deoxyuridine (dU) incorporation into DNA as thymidine, and to misincorporation of [3H]dU as dUMP. After a 15 min preincubation with up to 50 microM BW301U and a further 15 min incubation after addition of [3H]dU, the number of alkaline labile apyrimidinic sites increased with increasing drug dose, as demonstrated by alkaline sucrose gradient analysis. Significantly, new replication of DNA was inhibited only approximately 50% by 50 microM BW301U when [3H]dU incorporation was greater than or equal to 97% inhibited. Additional preliminary findings suggest that newly replicated DNA containing misincorporated dUMP is rapidly degraded in vivo by extensive excision-repair processes.
mesh_terms: D001402:B-Lymphocytes / Q000378:metabolism; D002460:Cell Line; D002843:Chromatin / Q000187:drug effects / Q000378:metabolism; D004247:DNA / Q000096:biosynthesis*; D004261:DNA Replication / Q000187:drug effects; D003839:Deoxyadenosines / Q000378:metabolism; D003856:Deoxyuracil Nucleotides / Q000378:metabolism; D003857:Deoxyuridine / Q000378:metabolism*; D005493:Folic Acid Antagonists; D006801:Humans; D007951:Leukemia, Myeloid / Q000378:metabolism; D008836:Micrococcal Nuclease / Q000378:metabolism; D011743:Pyrimidines / Q000494:pharmacology*; D013601:T-Lymphocytes / Q000378:metabolism
chemical_list: D002843:Chromatin; D003839:Deoxyadenosines; D003856:Deoxyuracil Nucleotides; D005493:Folic Acid Antagonists; D011743:Pyrimidines; D004247:DNA; C007267:2'-deoxyuridylic acid; D008836:Micrococcal Nuclease; C024530:piritrexim; D003857:Deoxyuridine