PROTEIN SYNTHESIS DURING DEVELOPMENT: CONTROL THROUGH MESSENGER RNA.

Utilization of long-lived messenger RNA appears to be the exception rather than the rule in cells which are differentiating and synthesizing large amounts of specialized product at the same time. The fact that polyribosomes synthesize protein after RNA synthesis is turned off by actinomycin D is used to demonstrate messenger RNA of long half-life. The data suggest that most tissues examined have short-lived messenger RNA's, but the ocular lens can synthesize protein after an incubation of 24 hours in 40 microg of actinomycin D per milliliter. A common basis for the presence of long-lived messenger RNA in the cells of the lens, the feather, and in reticulocytes is discussed.