Physical and chemical characterization of RNA incorporated by rabbit spleen cells

Rabbit spleen cells can incorporate a small but measurable amount of radioactively labeled rabbit lymph node RNA. At saturation, each cell can incorporate 4 × 10¹⁰ D of RNA that are resistant to the action of added RNase. Part of the incorporated ³H-RNA is protected from substantial degradation inside the cell for at least a few hours since high mol. wt (S > 12) ³H-RNA can be obtained from host cells upon re-extraction. Incorporated RNA was found in all three subcellular fractions analysed and had a nucleotide composition similar to that of input RNA. When bacterial RNA is used, the incorporation is significantly reduced and the incorporated RNA is rapidly degraded inside the cell. The presence of actinomycin D does not affect these results, indicating that the radioactivity inside the cells is not due to de novo synthesis utilizing degraded RNA.