Figure 4.

Nucleolar localization of MYBBP1A depends on nucleolar RNA. (A) Purification and identification of MYBBP1A-associated proteins. Nucleolar extracts prepared from MCF-7 cells (Control) or those stably expressing FLAG-tagged MYBBP1A (FLAG-MYBBP1A) were incubated with anti-FLAG antibody-conjugated agarose beads, and the bound proteins were eluted by FLAG peptides. Using mass spectrometry, MYBBP1A-interacting proteins were identified. NPM and EBP2 were identified in the same protein band. ^*Proteins that showed nonspecific binding. (B) MYBBP1A was translocated from the nucleolus to the nucleoplasm by RNase treatment. (Upper) Permeabilized MCF-7 cells were incubated in the absence (−) or presence (+) of RNase. They were subsequently fixed and stained with the indicated antibodies or DAPI. (Lower) The percentage of cells that showed translocation of UBF, MYBBP1A, or NPM from the nucleolus. Values are given as the mean±s.d. for triplicate experiments.