Isolation of oligo(U)-containing heterogeneous nuclear RNA from control and 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole-treated HeLa cells

Comparison of polyadenylic acid and oligouridylic acid messenger RNA associated proteins

Various subclasses of messenger ribonucleoprotein particles were prepared from free cytoplasmic and polysome fractions of rat liver on the basis of the homopolymeric content of the constituent RNA's. Two major proteins were evident in the free cytoplasmic preparations: the poly(A)-binding protein was the major constituent of polyadenylated components and a 60 kilodalton protein was the major protein in oligouridylated components. In addition to the poly(A)-binding protein, the polysome fractions contained a 74 kilodalton protein that was present in all subclasses of particles. With both free cytoplasmic and polysome preparations, chromatography on columns of poly(U)-sepharose separated poly-adenylated mRNP's largely on the basis of the length of the poly(A) tract; mRNP's containing short poly(A) tracts (fragment distribution centered on 34 residues) were not retained by the columns, presumably because of the interaction of the poly(A) with poly(A)-binding protein.

Improved preparation of poly(A) Sepharose and the isolation of oligo(U) containing heterogeneous nuclear RNA from Friend erythroleukemic cells

When poly(A) sepharose (prepared according to previously published procedures) was stored in aqueous buffer at 4 degrees C for 5 days or longer, it bound nonspecifically a high percentage of the input RNA which could not be eluted with formamide. We have found that treatment with ethanolamine, followed by dehydration with ethanol yielded poly(A) sepharose which was stable for many months and possessed a low degree of nonspecific binding. Chromatography on poly(A) sepharose permitted the specific isolation of that fraction of Friend erythroleukemic cell heterogeneous nuclear RNA (hnRNA) which contained oligo(U) sequences. Approximately 10% of the hnRNA which contained a poly(A) sequence [poly(A+)] also contained an oligo(U) sequence. Interestingly, prior HCHO denaturation of the hnRNA enhanced binding of the poly(A+) oligo(U+) hnRNA to poly(A) sepharose by tenfold. This suggested that the oligo(U) sequence may be in a region with secondary structure, possibly an intramolecular duplex with the 3' poly(A). Friend cell oligo(U) sequences ranged from 20 to 50 nucleotides in length and, thus, were similar to the oligo(U) sequences which heretofore had only been shown to be present in HeLa cell hnRNA. These results established that rodent cell hnRNA contain oligo(U) sequences and demonstrate, for the first time, that hnRNA containing both a poly(A) and an oligo(U) sequence can be separated from other classes of hnRNA. In addition, conditions are presented for the removal of HCHO from nucleic acid.