Stability of nuclear RNA in mammalian cells (original) (raw)

The kinetics of entry of [3H]adenosine into ATP, cellular RNA, and nuclear RNA of mouse L cells were determined and analyzed. A molar accumulation curve for RNA was estimated from the specific radioactivities of RNA and ATP; this curve wss resolved graphically into stable and unstable components. The stability of the unstable component (mostly heterogeneous nuclear RNA) was estimated by applying h&-order decay analysis. Heterogeneous, nuclear RNA decays with an apparently uniform half-life of 23 minutes, considerably greater than some previous estimates. It is synthesized at an instantaneous rate of 5.4 x 10e2 pg/cell per minute and reaches a steady-state level of l-8 pg/cell in the nucleus, or 7% of the total cellular RNA. Only about 2% of the heterogeneous RNA synthesized in L cells enters polysomes as messenger RNA. The implications of these values are discussed with reference to similarly determined values for sea urchin embryos.