Rate of Ovalbumin Messenger Ribonucleic Acid Synthesis in the Oviduct of Estrogen-primed Chicks

Abstract

Abstract The concentration of translatable ovalbumin messenger RNA in the tubular gland cells of the chicken oviduct was determined from estimates of relative rate of ovalbumin synthesis, polysome concentration, size of ovalbumin-synthesizing polysomes, DNA concentration, and percentage of tubular gland cells in the oviduct. During secondary stimulation with estrogen, the concentration of ovalbumin messenger RNA rose from undetectable levels to approximately 70,000 molecules per tubular gland cell after 5 days when a steady state was reached. The initial rate of ovalbumin messenger RNA accumulation was about 22 molecules per min per tubular gland cell. Nearly all the translatable ovalbumin messenger RNA was localized in polysomes, even at very early times after hormonal stimulation, suggesting that there is no free pool of untranslated messenger. The half-life of ovalbumin messenger RNA was estimated to be about 24 hours by labeling the RNA in vivo followed by subsequent purification and determination of its specific activity. Two other potential approaches for determining messenger half-life were shown to be unsuitable. Using the half-life value of 24 hours, the steady state rate of ovalbumin messenger RNA synthesis was about 34 molecules per min per tubular gland cell. Based on theoretical values for the maximum rate of messenger RNA transcription in eukaryotes, one ovalbumin gene per haploid genome is sufficient to maintain the observed rate of ovalbumin messenger RNA synthesis.