The effect of protein and RNA synthesis inhibitors on the synthesis and secretion of hCG, α- and β-hCG subunits, in organ culture

Abstract

The relationship between the rate of RNA and protein synthesis and that of hCG and its α- and β-subunits was studied in an organ culture system using RNA and protein synthesis inhibitors. It was found that inhibiting protein synthesis by puromycin or cycloheximide results also in a nearly complete inhibition of the synthesis and/or processing of RNA molecules. Protein synthesis was found to be dependent upon continuous poly A(−) RNA synthesis. The intracellular content of hCG, α-hCG and β-hCG remains constant during the entire incubation period and does not change in response to any of the inhibitors used. However, in the presence of some inhibitors, changes are observed in the amount of the secreted hormone and its two subunits as well as in the association ability of the subunits to form the complete native hormone. Nevertheless, synthesis and secretion of hCG, α-hCG and β-hCG were almost identically affected by α-amanitin. These results might suggest that the mRNAs coding for the two subunits have the same relative metabolic stability and/or that these mRNAs are mobilized molecules from free cytoplasmic mRNP pools. The specific α- and β-mRNAs seem to be less stable, however, than the mRNAs coding for the other newly synthesized proteins, since the inhibition of α- and β-hCG synthesis by α-amanitin was consistently higher than the corresponding average inhibition of total protein synthesis.