Modulation of the synthesis in vitro of a hormone-induced protein by transfer RNA

Abstract

WE have shown that transfer RNAs (tRNAs) and the enzymes which modify their structure at the macromolecular level (tRNA methyltransferases) are under hormonal control in the target tissue1–3. Oestrogen-induced, cell-specific protein synthesis in immature chick oviducts has been extensively studied4–6. Oestrogen induces cytodifferentiation of the primitive oviduct and the consequent synthesis by the tubular gland cells of ovalbumin, conalbumin, ovomucoid and lysozyme7. Continuous presence of oestrogen is required for the sustained synthesis of these proteins in immature chicks; withdrawal of oestrogen is accompanied by a gradual decline in cell-specific protein synthesis6. The tubular gland cells in the oviduct magnum, however, continue synthesising non-secretory proteins. Readministration of oestrogen to chicks after withdrawal (secondary stimulation) results in the restoration of the synthesis of cell-specific proteins without concomitant need for DNA synthesis. We report here that in an in vitro tRNA-dependent protein-synthesising system from Ehrlich ascites cells, stimulation of the translation of ovalbumin mRNA was significantly enhanced by tRNA extracted from the oviduct of oestrogen-stimulated immature chicks or from the oviduct of laying hens compared with tRNA from oviducts of withdrawn chicks. Therefore, the efficiency of synthesis in vitro of a hormone-induced protein can be regulated by tRNA.