FIG. 4.

The p175 isoform is present in a multiprotein complex. (A) Western blot analysis of fractions (numbers above the lanes) obtained by fractionation of the nuclear extract from Drosophila embryos on a Superose 6 column for the presence of TRF2 isoforms. The column was calibrated with thyroglobulin (670K) and ferritin (440K) standards. The same fractions were tested with antibodies against TBP and TAF4 as a control. (B) Western blot analysis of fractions eluted from a heparin-Ultrogel column for the presence of TRF2 isoforms. The nuclear extract was loaded in 0.15 M KCl. The bound proteins were eluted with a 0.25 to 0.75 M KCl gradient. The same fractions were stained with antibodies against TBP and TAF4 as a control. (C) Immunoprecipitation of the nuclear extract from Drosophila embryos with antibodies against p175 (Ab1). The immunoprecipitated complexes were washed with 500 mM KCl-containing immunoprecipitation buffer before complexes bound to antibody-coated beads were loaded on a sodium dodecyl sulfate-polyacrylamide gel electrophoresis gel for Western blot analysis with the indicated antibodies. To check the specificity of coimmunoprecipitation, the proteins bound to antibody-coated beads were stained with antibodies against TBP.