FIG. 5.

A 40-kDa protein in nuclear extracts from 0- to 6-h embryos is UV cross-linked to probe 5-4. End-labeled probe 5-4 was incubated with nuclear extracts from 0- to 6-h embryos (lanes 2 to 9) or 6- to 12-h embryos (lanes 11 to 18), or with buffer only (lanes 1 and 10), under the same conditions as those used for EMSA except that a lower concentration of poly(dI-dC) was used. After a 30-min incubation at room temperature, the samples were treated with UV light (using a UV cross-linker) for 10 min and then analyzed on a 10% acrylamide-SDS gel. Competition experiments using either wild-type (wt) or mutant 5-4 probes (lanes 3 to 9 and 12 to 18) were performed as described for the EMSA experiments in Fig. 4C. The positions of size markers and the ∼40-kDa band (solid arrowhead) are indicated on the left.