[A novel group of nucleolar organizer region associating proteins]

With the scleroderma autoantinucleolar antiserum which was discribed in our previous paper, we identified a novel group of nucleolar organizer associating proteins, ANOP. By means of immunoblotting, it was found that ANOP mainly consists of three polypeptides with molecular weights of 65, 76, and 78 KD respectively. Immunoelectron microscopy demonstrated that ANOP is localized in the shells of dense fibril components surrounding fibrillar centers of nucleolus. Moreover, indirect immunofluorescence studies on various cells of vertebrate animals indicated that ANOP is a group of highly conserved nucleolar antigens. The fibrillar centers of human, mouse, chinese hamster, chicken, frog and crucian carp cells can all be brightly stained by ANOP specific antiserum. However, it was found that in amphibian, the erythrocytes and the early embryo cells prior to gastrulation are devoid of ANOP. During gastrulation, ANOP begins to appear in the nuclei, and then, the content of ANOP in nucleoli apparently increases gradually. These phenomena suggest that ANOP may take a role in rRNA gene activity.