Spatial association of prekinetochores and chromocentres in the interphase nuclei of mouse cultured fibroblasts.

The structure and spatial distribution of prekinetochores and chromocentres (centromeric heterochromatin) in the interphase nuclei of mouse fibroblasts were studied by light and electron microscopy. Using the autoimmune serum GS reacting with centromeric proteins CENP-A, B, C in mammalian cells, we showed that most interphase prekinetochores were associated with chromocentres. During the interphase S period, including DNA replication in chromocentres, the macroorganization of chromocentres and their association with prekinetochores were maintained. Using cryosections and the electron microscopy immunogold technique, we found that centromeric proteins were mainly located at the chromocentre periphery. Nevertheless, we failed to find any definite kinetochore structures including those usually observed during mitosis at the sites of protein binding. Only small associates of fibrous material, presumably, corresponding to centromeric proteins, could be observed in association with the interphase mouse chromocentres in both cryosections and conventionally fixed sections.