Regulation of protein synthesis in mammalian cells: II. Inhibition of protein synthesis at the level of initiation during mitosis

Abstract

The decline in the rate of protein synthesis during mitosis in eukaryotic cells was studied using Chinese hamster ovary cells arrested in metaphase with Colcemid. The rate of protein synthesis in mitotic cells is approximately 30% of the interphase rate. Ribosomes become attached to messenger RNA and initiate polypeptide synthesis at a reduced rate. After initiation of polypeptide synthesis, ribosomes are translated at a normal rate. Reducing the rate of translation with low levels of cycloheximide mobilizes a large proportion of monomeric ribosomes into active polyribosomes. The amount of messenger RNA associated with polyribosomes is also increased in mitotic cells treated with cycloheximide. It appears that the reduced protein synthesis during mitosis results from a lowered rate of attachment of ribosomes to messenger RNA and initiation of polypeptide synthesis.