Purification of low-abundance messenger RNAs from rat liver by polysome immunoadsorption.

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Abstract
Three low-abundance hepatic mRNA were purified to near homogeneity by polysome immunoadsorption. The mRNA coding for the precursor of ornithine transcarbamoylase [carbamoylphosphate:L-ornithine carbamoyltransferase, EC 2.1.3.3], the precursor of the .beta.-subunit of propionyl-CoA carboxylase [propionyl-CoA:carbon dioxide ligase (ADP-forming), EC 6.4.1.3] and cystathionine .beta.-synthase [L-serine hydro-lyase (adding homocysteine), EC 4.2.1.22], representing approximately 0.20, 0.02 and 0.015% of total hepatic mRNA, respectively, were purified 450-6300-fold. The following steps were used: interaction of rat liver polysomes with an IgG fraction of monospecific antisera raised against each polypeptide; immobilization of polysome-antibody complexes on a protein A-Sepharose column; removal of the bulk of polysomes by extensive washing; dissocation of ribosomal subunits and elution of specific mRNA with EDTA; and isolation of the eluted mRNA by chromatography on an oligo(dT)-cellulose column. This procedure will permit isolation of other low-abundance mRNA and subsequent cloning of their respective c[complementary]DNA.