ABSTRACT
This chapter presents the intranuclear protein accumulation and its biological significance by the experimental findings on an SV40 virus-induced tumor and chicken erythrocyte hybrid. It shows that Platelet Derived Growth Factor (PDGF), by binding to elements of the cytoskeleton, modifies the intracellular protein transport in favor of an accumulation of proteins into the nuclei. The facilitated cell growth, either the activation of dormant cells or the reactivation of both daughter cells after division in case of tumor cells, has long been considered to be one of the most important open questions of cell biology. The growth factor peptides, including the PDGF and the transforming factors of tumor cells, have been considered as the signal molecules for activation of the cell growth. PDGF induced a significant intranuclear accumulation of the labeled proteins, but there was no difference in the total grain number of the PDGF-treated and -untreated cells.
