C. elegans Mediator complexes are expressed in all cell types and are localized in the nuclei. Wild-type embryos were stained with CeMed6 preimmune serum (A), CeMed6 Ab (B), or CeMed10/CeNut2 Ab (C). To compare the localization pattern of CeMed6 with that of pol II, wild-type embryos were stained with CeMed6 Ab (E) or pol II Ab (F), and the proteins were visualized by using indirect immunofluorescence. Embryos also were stained with 4′,6-diamidino-2-phenylindole (D) to show the location of nuclear DNA.