FIG. 6.

Immunoprecipitated complexes are parts of the pre-rRNP particles. (a) Nuclear extract prepared from the FLAG-NNP-1 and HA-ubiquitin cotransfected 293 EBNA cells was fractionated on a 10 to 40% sucrose gradient with continuous monitoring of the absorbance at 254 nm. The FLAG-NNP-1-associated pre-rRNP complex was immunoisolated from each of the 40S, 60S, and 90S fractions; separated by SDS-PAGE (b); and analyzed by Western blotting with anti-HA (c) and anti-FLAG (d) antibodies, respectively. N, NNP-1-associated pre-rRNP complex isolated from FLAG-NNP-1-transfected cells.