Monoclonal antibodies detect conformational abnormality of uracil DNA glycosylase in Bloom's syndrome cells.

The immunoreactivity of normal human and Bloom's syndrome uracil DNA glycosylase was examined using a series of three anti-human placental uracil DNA glycosylase monoclonal antibodies. Immunoreactivity was determined by three separate and independent criteria: enzyme-linked immunosorbent assay (ELISA), enzyme inhibition studies and immunoblot analysis. As defined by each criteria, normal human uracil DNA glycosylase was immunoreactive with each antibody (37.04.12, 40.10.09 and 42.08.07). In contrast, each glycosylase purified from two separate non-transformed Bloom's syndrome cell strains was not reactive with antibody 40.10.09. First, no ELISA reactivity was observed with each glycosylase protein. Second, catalysis by each Bloom's syndrome glycosylase was not inhibited by antibody 40.10.09. However, each Bloom's syndrome enzyme was immunoreactive with antibodies 37.04.12 and 42.08.07. No immunoreactive glycosylase species was observed during the induction of the Bloom's syndrome enzyme during cell proliferation. However, immunoreactivity of the denatured Bloom's syndrome enzyme with 40.10.09 antibody was observed by immunoblot analysis. These results suggest that Bloom's syndrome uracil DNA glycosylase is characterized by a structural alteration in the native glycosylase protein secondary to the primary antigenic site recognized by the 40.10.09 antibody. This altered antigenicity may provide an immunological marker for the identification of this human genetic syndrome.