HISTONE H1O IS SYNTHESIZED BY HUMAN LYMPHOCYTIC LEUKEMIA CELLS BUT NOT BY NORMAL LYMPHOCYTES

Using a two-dimensional gel electrophoresis system (sodium dodecyl sulphate/acetic acid-urea-hexadecyltrimethylammonium bromide) coupled with fluorography, we investigated the synthesis of H1 isoproteins in leukemic cells obtained from peripheral blood of eight children suffering from acute lymphoblastic leukemia (ALL) (four T-ALL, three common ALL, and one B-ALL) and in normal peripheral lymphocytes. H1.degree. was synthesized in leukemic cells but not in normal lymphocytes. Inhibition of DNA synthesis with hydroxyurea and 1-.beta.-D-arabinofuranosylcytosine induced an increase of relative synthesis of H1.degree. in leukemic cells but did not induce any detectable synthesis of H1.degree. in normal lymphocytes. H1.degree. synthesis was also undetectable in peripheral lymphocytes of leukemic children in complete remission after chemotherapy and in lymphocytes of a homozygotic twin of a leukemic patient. H1.degree. may be a marker of malignant transformation of lymphocytes and as such could be of use for early detection of relapse in patients with acute lymphocytic leukemia in apparent complete remission.