QUANTITATIVE VARIATION IN SERINE TRANSFER RIBONUCLEIC ACID DURING ESTROGEN-INDUCED PHOSPHOPROTEIN SYNTHESIS IN ROOSTER LIVER

In roosters, hepatic synthesis of the yolk phosphoprotein, phosvitin, is induced by estrogen treatment. Phosvitin has an unusually high content of serine residues (over 50%), and an attempt was made to correlate phosvitin induction with changes in the benzoylated DEAE-cellulose chromatographic profile of in vitro acylated seryl transfer ribonucleic acid. Plasma phosvitin was used as an indicator of phosvitin induction, as newly synthesized phosvitin does not accumulate in the liver. Plasma phosvitin levels increased 150-fold after a single injection of estradiol-17β. Transfer ribonucleic acid and aminoacyl transfer ribonucleic acid ligases were prepared from livers of normal and estrogen-treated roosters. Unfractionated transfer ribonucleic acid isolated during the initial stimulatory period of phosvitin synthesis was acylated with serine to a significantly greater extent than was transfer ribonucleic acid from control animals, regardless of the source or concentration of ligase, concentration of transfer ribonucleic acid, duration of acylation incubation, or isotopic label. At least four seryl transfer ribonucleic acid peaks were observed in chromatograms of acylated transfer ribonucleic acid derived from control or estrogen-treated roosters. A marked relative increase in one major and in one minor peak was found during the rapid phase of phosvitin synthesis. This change in seryl transfer ribonucleic acid chromatographic pattern was independent of the isotopic label and the source of ligase. With decreasing levels of plasma phosvitin these changes in seryl transfer ribonucleic acid diminished and approached the control profile. Identical seryl transfer ribonucleic acid changes were again noted after a second dose of estradiol-17β. Similar chromatographic comparisons of aminoacyl transfer ribonucleic acids for glycine, alanine, valine, leucine, phenylalanine, tyrosine, threonine, methionine, arginine,histidine, lysine, and aspartic and glutamic acids before estrogen injection and during the initial rapid phase of phosvitin synthesis did not reveal major specific changes comparable to those observed in seryl transfer ribonucleic acid. Only small changes in minor species of glycyl, histidyl, and glutamyl transfer ribonucleic acid were observed. The correlation between phosvitin synthesis and specific seryl transfer ribonucleic acid levels, the relative lack of change in other aminoacyl transfer ribonucleic acids, and the predominance of serine in phosvitin suggest that the estrogen-induced seryl transfer ribonucleic acid alterations are related to phosvitin induction. © 1969, American Chemical Society. All rights reserved.