EIF6 exists both in nucleolus and cytoplasm. The 40S pre-ribosome is transported out of the nucleolus and into the cytoplasm. In eukaryotes, it takes place both in the cytoplasm and in the nucleolus. Their nuclei are irregularly shaped, contain clear chromatin, and possess an eosinophilic nucleolus. The nucleolus also disappears during early prophase. The main roles of the nucleolus are to synthesize rRNA and assemble ribosomes. The nucleolus, which makes ribosomes in the cell, also disappears. It has a nucleus with a prominent nucleolus. Besides the nucleolus, the nucleus contains a number of other nuclear bodies. In mammals, the nucleolus of the oocyte is derived solely from maternal cells. The mature r-proteins are then "imported" back into the nucleus and finally the nucleolus. The rRNA and RNA processing factors form large aggregates called the nucleolus. CBs are bound to the nucleolus by coilin proteins. Three of the rRNA molecules are synthesized in the nucleolus, and one is synthesized elsewhere. It accumulates mainly in the nucleolus where it forms stable complexes with NPM or Mdm2.