Association of a possible DNA ligase deficiency with T-cell acute leukemia.

DNA ligase activities were determined in blood samples of 431 different cases of lymphoblastic and nonlymphoblastic leukemia. Less activity was observed in samples from lymphoblastic patients. RNA translation together with ligase immunoprecipitation experiments show that in T-cell acute lymphoblastic leukemic cells, no ligase is translated.

[Enzymes involved in the metabolism, replication and repair of DNA in acute leukemias (DNA ligases)].

DNA ligases are involved in DNA replication, repair and recombination. Consecutively to partial purification, these enzymes have been studied in acute leukemias and subclasses. There is a good correlation between this enzyme activity and the percentage of cells in S phase in acute myeloblastic leukemia.

Differentiation of thymocytes during human ontogeny: stage-specific DNA ligase in relation to terminal deoxynucleotidyl transferase, cell size and surface antigen.

The activities of two forms (7.5 and 5.5 S) of DNA ligase and of terminal deoxynucleotidyl transferase (TdT) have been studied in human thymocytes at different ages from 20 weeks pre-natal to 37 years after birth.

Inhibition of DNA ligase from human thymocytes and normal or leukemic lymphocytes by antileukemic drugs.

Human DNA ligase was purified from both normal and leukemic peripheral lymphocytes and normal thymocytes. The activity of the purified enzymes was assayed in the presence of several widely used antileukemic drugs. Melphalan and prednisone at 5 mM had no effect.

Effects of antileukemic agents on the activity of terminal deoxynucleotidyl transferase from human normal thymic and leukemic cells "in vitro".

Several widely used and experimental antileukemic drugs have been tested on the activity of Terminal deoxynucleotidyl Transferase (TdT) purified from normal human thymocytes and T-derived acute lymphoblastic leukemia peripheral blood lymphoblasts. The majority of these inhibitors were equally potent inhibitors of the enzyme from thymocytes or leukemic lymphocytes. Adriamycine and etoposide were more potent inhibitors of the enzyme purified from thymocytes.