Thyroglobulin Messenger RNA: Translation of a 33‐S mRNA into a Peptide Immunologically Related to Thyroglobulin

Publisher Website
Google Scholar
Abstract
Poly(U)‐Sepharose chromatography of the RNA extracted from a thyroid fraction sedimenting between 800 ×g and 27000×g allows the purification of two RNA fractions amounting each to 1% of the applied material. The first one is loosely bound to the column from which it is eluted at 25°C. It is mainly composed of 16‐S and 12‐S RNA comprising no poly(A) sequences. This could correspond to mitochondrial rRNA. The second one, which is eluted at 50°C, is poly(A)‐rich and represents 33‐S and 17‐18‐S RNA species. The 33‐S RNA resists heating at 80°C, suggesting that it is composed of one polynucleotide chain. When injected into Xenopus oocytes, the 33‐S RNA specifically promotes the synthesis of a peptide with an apparent molecular weight of 185000 and an apparent sedimentation coefficient of 10‐S. This peptide is immunologically related to thyroglobulin and could represent its main precursor. Under the conditions tested it does not polymerize spontaneously into 19‐S thyroglobulin, suggesting that assembly of the molecule could require specific, post‐translational alterations of the precursor and/or the presence of additional lighter subunits.