FIG. 4.

A specific amino-terminal region of SAP 155 is sufficient to mediate the interaction with U2AF. (A) Structure of SAP 155. The amino-terminal RWDETP and TPGH repeats and carboxy-terminal PP2A-like repeats are shown (29). Numbers indicate amino acids. The portions of SAP 155 that were used to make fusion proteins are indicated. (B) Coomassie stain of GST fusion proteins. Markers are indicated to the left in kilodaltons. (C) Lanes 1 to 6: GST fusion proteins bound to glutathione beads were incubated with a 25-μl aliquot of nuclear extract and washed, and then Western analysis of the bound proteins was carried out. Total nuclear extract (NE) (4 μl) is shown in lane 7. The blot was probed successively with U2AF⁶⁵, U2AF³⁵, and SAP 130 antibodies.