Quantitative Electron Microscopy of Intracytoplasmic Type A Particles at Kinetochores of Metaphase Chromosomes Isolated from Chinese Hamster and Murine Cell Lines

Abstract

Individual chromosomes of [Chinese hamster ovary] CHO-KI cells were successfully isolated and spread for EM karotyping. Controlled preparation permitted a quantitative evaluation of the association between endogenous intracytoplasmic type A virus precursor particles and the centromeric region (kinetochores) of isolated chromosomes at prophase and metaphase. The transfer of type A particles from the cytoplasmic to the centromeric regions during early metaphase in conjunction with microtubule assembly at a time when the kinetochores are structurally mature and capable of binding microtubules. Preliminary comparable studies of the endogenous M432 virus propagated in murine cells support these findings. The results are discussed with respect to mechanisms of intracellular movement of virus precursor particles and the interference with components of both the cytoskeleton and the mitotic apparatus.