Figure 6.

Immunoblot analysis of RNP complexes immunopurified from metaphase-arrested HeLa cells. RNP complexes were immunopurified with either monoclonal antibody 4F4 or 7G2 from metaphase-arrested HeLa cells (lanes +). The proteins in the respective complexes were resolved by SDS-PAGE and blotted onto nitrocellulose. Identical filters were probed with antiserum to fibrillarin, a monoclonal antibody to B23, or 4B10 monoclonal antibody to hnRNP A1, as indicated. Lanes - contain mock immunopurifications carried out without HeLa cell lysate, to ascertain whether any of the signal observed is due to the antibodies used in the immunopurification. Ig l.c. refers to the Ig light chains originating from the antibody used for immunopurification, and which are detected by the secondary antibody used in the immunoblot.