Some properties of mammalian DNA-like RNA isolated by chromatography on methylated bovine serum albumin-kieselguhr columns

The Chromatographic behavior of mammalian DNA-like RNA on columns of methylated bovine serum albumin adsorbed on kieselguhr (MAK) has been studied. The peculiarly tenacious binding of the DNA-like RNA to MAK permits its separation from the other nucleic acids during salt elution. MAK columns will differentiate between two forms of DNA-like RNA; one is eluted by the salt gradient and has a high sedimentation velocity (50 s), the other needs more vigorous elution and has a lower modal sedimentation coefficient (16 s). Both types of DNA-like RNA are rapidly synthesized. The kinetics of ³²P incorporation into them are qualitatively consistent with a role for the 50 s moiety as precursor to the 16 s fraction. The 16 s type of DNA-like RNA resembles messenger RNA in rate of synthesis, sedimentation pattern, composition, tenacity of binding to MAK and in the relative amount in the cell, and is, therefore, tentatively identified with it, at least in part. It is proposed that the synthesis of at least some of the DNA-like RNA of the mammalian cell, like that of ribosomal RNA, is polycistronic.The tenacious binding of the DNA-like RNA to MAK columns can be used to isolate this RNA rapidly. The resulting fraction is purified at least sevenfold with respect to the other nucleic acids of the cell. This DNA-like RNA constitutes approximately 7% of the cell nucleic acid.The 28 s and 18 s units of HeLa cell ribosomal RNA were found to differ considerably in composition. They were shown to be eluted from MAK columns in the order of increasing sedimentation values.