Translational control during early Dictyostelium development: possible involvement of poly(A) sequences.

A rapid decrease in the translational efficiency of mRNA synthesized during vegetative growth is associated with the initiation of development in Dictyostelium discoideum. In contrast, newly synthesized mRNA associates with polysomes with high efficiency. Discrimination between these two mRNA populations correlates with a rapid shortening of the poly(A) tract on the preexisting mRNA. A model is proposed in which a critical poly(A) length regulates the pattern of protein synthesis by affecting the efficiency with which mRNAs can interact with the translational machinery. The model suggests that transcriptional and translational controls can be coupled by altering the state of adenylation of the preexisting mRNA population. The model allows radical changes in the pattern of protein synthesis without wholesale destruction of preexisting mRNA.