The isolation of wool keratin messenger RNA from sheep

A method for the isolation of polysomal RNA from plucked wool follicle tissue is described. When translated in a reticulocyte lysate cell-free system, the products encoded by the RNA are electrophoretically identical to the low-sulfur and high-sulfur wool keratins. Since non-keratin translation products were not detected, the keratin mRNA species appear to be the predominant messenger component of the polysomal RNA. Sucrose gradient fractionation of the polysomal RNA gave rise to 2 discrete peaks of keratin mRNA, with mean sizes of 21S and 11S. The 21S fraction coded for the low-sulfur and larger high-sulfur wool keratins, while the 11S fraction coded for proteins smaller than about 20000 daltons, possibly the high-tyrosine keratins and smaller high-sulfur keratins. The keratin mRNA can be separated from the bulk ribosomal RNA by oligo(dT) cellulose chromatography, and hence is presumed to contain a terminal poly(rA) tract.