Production and characterization of monoclonal antibodies to the steroid receptor coactivator AIB1

The steroid coactivator AIB1 (Ampified In Breast cancer 1) is a member of t he SRC-1 family of transactivation coactivators that is amplified in about 7% of breast tumor samples. Hybridomas were established that secreted monoc lonal antibodies (MAbs) to a recombinant glutathione-S-transferase (GST) fu sion protein expressing the steroid receptor interacting domain of AIB1 (GS T-AIB.T1: a.a. 605-1294). Four MAbs from these hybridomas were characterize d and designated AX15.1, AX15.2, AX15.3, and AX15.4. The MAbs were shown to be specific to AIB1 and did not cross-react with two similar coactivators SRC-1 and TIF2 as shown in Western blot analysis and enzyme-linked immunoad sorbent assay (ELISA), Western blot analysis using the four MAbs showed spe cific recognition of AIB1 protein as a 160 kDa band in lysates from cell li nes containing AIB1 gene-amplification. The MAbs immunoprecipitated in vitr o-translated AIB1 and cellular AIB1 from metabolically labeled cells. The r esults show that these newly described MAbs are useful in studies of AIB1 f unction and expression.