Synthesis and turnover of nuclear proteins

Abstract

1. The turnover of proteins labeled with tritiated amino acids has been followed over several cell cycles in Chinese hamster cells in culture. Radioactive proteins are no longer detectable in chromosomes of the third metaphases following labeling. The experiment is interpreted as evidence of general turnover of chromosomal proteins (including histones) during cell growth and division. 2. In labeling experiments with amoeba all nuclear proteins were found to undergo turnover, even in the absence of cell division. 3. C14 amino acid labeling suggests that a small amount of histone synthesis may take place in the pre- and post-DNA synthesis periods.