Comparison of RNase T₁ Fingerprints of U1, U2, and U3 Small Nuclear RNA's of HeLa Cells, Human Normal Fibroblasts, and Novikoff Hepatoma Cells¹

To determine whether there are differences between the U1, U2, and U3 small nuclear RNA's of human cancer cells (HeLa cells) and human normal fibroblasts (IMR-90 cells), and between these uridine-rich small nuclear RNA's of human and Novikoff hepatoma cells, the cells were first incubated in Eagle's medium with [³²P]P₁ to label these RNA's uniformly.

No differences were found between the RNase T₁ fingerprints of the purified U1, U2, and U3 RNA's of HeLa cells and IMR-90 cells. The RNase T₁ fingerprints of U1 RNA's from human tissues were very similar to that of the U1 RNA of Novikoff hepatoma cells. The RNase T₁ fingerprints of U2 and U3 RNA's from human tissues had many similarities to those of Novikoff hepatoma cells, but a few differences were found, such as a point mutation of the U-U-Gp in the rat U2 RNA to A-U-Gp (U → A) in human U2 RNA. Unlike the three U3 RNA's of Novikoff hepatoma cells, U3 RNA from human tissues appears to be only one species.

These results indicate that U1, U2, and U3 RNA's of human cancer cells are essentially the same as those of human normal cells. In addition, the uridine-rich small nuclear RNA's appear to be conserved through evolution.