Immunocytochemical localization of nucleophosmin and RH-II/Gu protein in nucleoli of HeLa cells after treatment with actinomycin D

HeLa cells were studied with the use of light microscopical immunocytochemi stry to obtain more information on the nucleolar localization of nucleophos min (B23 protein) and RH-II/Gu protein. In control cells these proteins are colocalized. After structural rearrangement of nucleoli induced by actinom ycin D, nucleophosmin was present in the nucleolar periphery and nucleolar peripheral caps. In contrast, RH-II/Gu protein was observed mainly in centr al regions of nucleoli as a compact body. However, in some nucleoli the pro teins colocalized in a small portion of the peripheral nucleolar cap. The p roteins were also colocalized in micronucleoli but occasionally RH-II/Gu pr otein was absent or both proteins were not present.