Protein synthesis, retinoid control

The experiments of Lotan et al. (1982a) showed decreases in the poly(A)+RNA population of S91 melanoma cells cultured for 5 days in the presence of 10 retinoic acid as compared to controls. Such treatment results in nearly 90% inhibition of the growth of the cells. Protein synthesis by these cells was depressed relative to control cultures, as evidenced not only by the decreased poly(A) + RNA levels but also by decreases in the proportions of ribosomes in polysomes and decreases in polysome-associated mRNA. In contrast to the effects of Omori and Chytil (1982) on a differentiating epithelial tissue, Lotan et al. (1982a) found little qualitative differences in the protein patterns of treated or control cells. Further experiments should help answer the question of whether the underlying mechanisms of retinoid control of growth and differentiation are distinct or identical. 

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