Entry of mRNA into polyribosomes during recovery from starvation in mouse sarcoma 180 cells.

Starvation in mouse sarcoma 180 cells leads to a block in initiation of protein synthesis which results in the conversion of polysomes to 80-S ribosomes. The mRNA is released as nucleoprotein particles. Addition of nutrients to the starved cell causes the rapid uptake of the mRNA into large polysomal structures. The ribosomes enter these structures more gradually, without much effect on the sedimentation profile of the labeled mRNA. The results indicate that the stored mRNA in starved cells is readily available for uptake into polysomes. They also suggest that the mRNA may be binding to components other than ribosomes during the initial stages of polysome formation.