PML and Sp1 are tightly associated in the core nuclear matrix.

<p>U2OS/Vec (a) and U2OS/PML (b) cells were treated with 100 µM ZnSO₄ for 12 h to induce PML4 expression. Numbers 1 though 5 represent different protein fractions isolated from a and b cells according to the procedure described in the material and methods. Different fractions obtained from the NM fractionation were resolved in an acrylamide gel, stained with Coomassie blue (A), and Western blotting analysis with the indicated antibodies (B). Lamin B1 was used as a marker for nuclear matrix-associated fraction. C. A small portion of the remaining cells from fraction 5 were cytocentrifuged onto microscope slides and then double-color immunofluorescence staining of PML and Sp1 in the nuclear matrix core was performed using PML monoclonal and Sp1 polyclonal antibodies.