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Base Composition of High Molecular Weight Nuclear RNA of Walker Tumor and Liver of the Rat¹

( Department of Pharmacology, Baylor University College of Medicine, Houston, Texas)

The high molecular weight nuclear RNA³ of the Walker 256 carcinosarcoma and normal rat liver was fractionated into 45 S and 55 S components by means of repeated sucrose density gradient centrifugations. The RNA was characterized by base composition determined by ultraviolet analysis and by distribution of ³²P-orthophosphate after pulse-labeling in vivo. In both the tumor and normal liver, the 45 S RNA had a relatively higher content of guanylic and cytidylic acid than the 55 S fraction. Ultraviolet absorption analysis showed that both the 45 S and the 55 S RNA of the Walker tumor had a significantly lower content of adenylic and uridylic acids than the corresponding fractions from the normal liver. Studies with ³²P-orthophosphate revealed that the rapidly-labeled high molecular weight RNA of the Walker tumor had a markedly lower content of adenylic acid than the rapidly-labeled RNA of the liver. These data are supportive of the concept that there are significant differences in the RNA produced by the Walker tumor and the liver.

¹ These studies were supported in part by grants from the National Science Foundation, the USPHS (CA-05421, CA-07201), the Jane Coffin Childs Fund, and the American Cancer Society.

³ The following abbreviations are used: A, adenine or adenylic acid; A+U/G+C, ratio of the sum of the percentages of bases in adenylic and uridylic acids to the sum of the bases in guanylic and cytidylic acids, or the ratio of the sum of the percentages of the total ³²P in adenylic and uridylic acids to the sum of the percentages of the total ³²P in guanylic and cytidylic acids; C, cytosine or cytidylic acid; DNA, deoxyribonucleic acid; EDTA, disodium ethylenediamine tetraacetate; G, guanine or guanylic acid; PCA, perchloric acid; RNA, ribonucleic acid; S, sedimentation coefficient; SDS, sodium dodecylsulfate; U, uracil or uridylic acid.

² On leave from the Research Institute for Tuberculosis, Leprosy and Cancer, Tohoku University, Sendai, Japan.

Received 12/11/64.