FIGURE 2.
Analysis of unlabeled nuclear proteins by sucrose gradient fractionation and immunoprecipitation using anti-U1 70k antibody, mAb 2.73. Unlabeled nucleoplasmic extract was fractionated on a 5%–30% sucrose gradient. Every other fraction was immunoprecipitated with mAb 2.73 as in Figure 1. The precipitates were then separated on a 10% SDS-PAGE gel and subjected to Western analysis probing with mAb 2.73. The position of U1 70K protein, the unknown 120–130-kD proteins (X), and the immunoglobulin heavy chain (hc) are indicated.
