FIG. 1.

PHO interacts with PcG proteins and the BRM complex in Drosophila embryo nuclear extracts. (A) Coimmunoprecipitation experiments with antiserum directed against PHO with Drosophila embryo nuclear extracts. Nuclear extracts were incubated with either preimmune serum (lane 2) or antiserum directed against PHO (lane 3), followed by the addition of protein A beads. Following extensive washes with a buffer containing 250 mM NaCl and detergent, associated proteins were eluted with a buffer containing 1 M NaCl, resolved by SDS-PAGE, and analyzed by Western immunoblotting with antibodies directed against BRM (39), MOR (SN670 and SN671, pooled), OSA (74), PH (SN964), PC (SN965), PSC (49), GRO (PV1 and PV2, pooled), and the 140-kDa subunit of RNA polymerase II (Pol-II; DmRP140) (PV35). Lane 1 represents 10% of the input material used in the binding reactions. (B) The ability of a GST-tagged full-length PHO to recruit PcG proteins or the BRM complex within an embryo nuclear extract was tested by GST pulldown assays. GST alone (lane 2) or GST-PHO was immobilized on glutathione-Sepharose beads and incubated with Drosophila embryo nuclear extracts. Following a series of extensive washes with a buffer containing 150 mM NaCl, bound proteins were resolved by SDS-PAGE and analyzed by Western immunoblotting. Lane 1 represents 10% of the input material used in the binding reactions.