The first correct interpretation of this phenomenon was given by Johnson and Rao following their carefully designed experiment (Johnson and Rao, 1970). They observed a typical appearance of “shattered” or “pulverized” chromosomes following virus infection of cells, and they thought that the “pulverized” chromatin represented chromosomal fragments induced by the virus. The first observation of PCC was reported in virus mediated multinucleated fused cells of interphase and mitotic cells (Kato and Sandberg, 1967). This phenomenon is known as premature chromosome condensation (PCC). However, in certain circumstances, chromosome condensation may be uncoupled from mitotic events. In ordinary circumstances, chromosomes condense in mitotic phase only, under highly ordered molecular events. This method is much simpler than fusion-induced PCC, and has already proven useful in different fields. While fusion-induced PCC exploits the action of external maturation/mitosis promoting factor (MPF), migrating from the inducer mitotic cell to the interphase recipient, drug-induced PCC exploits protein phosphatase inhibitors, which can activate endogenous intracellular MPF. The novel drug-induced PCC method was introduced about 10 years ago. The method paved the way to a great number of fundamental discoveries in cytogenetics, radiation biology, and related fields, but it has been hampered by technical difficulties. More than 30 years ago, the first report of PCC in interphase cells fused to mitotic cells using Sendai virus was described (virus-mediated PCC). For example, using PCC we can visualize genetic damage shortly after the exposure to clastogenic agents. Besides, PCC has proved to be an useful tool for analyzing chromosomes in interphase. This phenomenon is known as “premature chromosome condensation (PCC).” PCC provides insights in the mechanisms of chromosome condensation, thus helping clarifying the key molecular events leading to the mitosis. However, condensation can be uncoupled from mitotic events under certain circumstances.
A basic principle of cell physiology is that chromosomes condense during mitosis.
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